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Rosetta stone"7 hours of terror" Philae approaches 67P/Churyumov-Gerasimenko
Surprising dunes on comet Chury
February 22, 2017

[Image: surprisingdu.jpg]
Left, an image of comet Chury showing outgassing of water vapor, which entrains dust. Right, the neck region, between the comet's two lobes. Various types of relief can be seen, including the dunes, at bottom left (circled in red), in the sandy region. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)
Surprising images from the Rosetta spacecraft show the presence of dune-like patterns on the surface of comet Chury. Researchers at the Laboratoire de Physique et Mécanique des Milieux Hétérogènes (CNRS/ESPCI Paris/UPMC/Université Paris Diderot) studied the available images and modeled the outgassing of vapor to try to explain the phenomenon. They show that the strong pressure difference between the sunlit side of the comet and that in shadow generates winds able to transport grains and form dunes. Their work is published on 21 February 2017 in the journal PNAS.

The formation of sedimentary dunes requires the presence of grains and of winds that are strong enough to transport them along the ground. However, comets do not have a dense, permanent atmosphere as on Earth. Nonetheless, the OSIRIS camera on board the Rosetta spacecraft showed the presence of dune-like forms approximately ten meters apart on 67P/Churyumov-Gerasimenko. They are found on the lobes of the comet as well as on the neck that connects them. Comparison of two images of the same spot taken 16 months apart provides evidence that the dunes moved and are therefore active.
Faced with this unexpected finding, the researchers show that there is in fact a wind blowing along the comet's surface. It is caused by the pressure difference between the sunlit side, where the surface ice can sublimate due to the energy provided by the sunlight, and the night side. This transient atmosphere is still extremely tenuous, with a maximum pressure at perihelion, when the comet is closest to the Sun, 100 000 times lower than on Earth. However, gravity on the comet is also very weak, and an analysis of the forces exerted on the grains at the comet's surface shows that these thermal winds can transport centimeter-scale grains, whose presence has been confirmed by images of the ground. The conditions required to allow the formation of dunes, namely winds able to transport the grains along the ground, are thus met on Chury's surface.
This work represents a step forward in understanding the various processes at work on cometary surfaces. It also shows that the Rosetta mission still has many surprises and discoveries in store.
[Image: 1x1.gif] Explore further: Image: Rosetta's shadow crosses Comet 67P/Churyumov–Gerasimenko in daring encounter
More information: Pan Jia et al. Giant ripples on comet 67P/Churyumov–Gerasimenko sculpted by sunset thermal wind, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1612176114 
Journal reference: Proceedings of the National Academy of Sciences [Image: img-dot.gif] [Image: img-dot.gif]
Provided by: CNRS

Read more at:[/url]

Angle of Repose

Why are volcanoes shaped the way they are? Why do they all look conical?*

[Image: fuji.jpg]Mount Fuji (Image: 
hoge asdf)[/size]

*I've been reliably informed that not all volcanoes are conical. In fact it is only cinder cone volcanoes that have this shape. Shield, Dome and Composite volcanoes have different shapes to reflect the different processes of how they are formed.

It's a similar shape to piles of sand, piles of grain, and sand dunes. If you pour salt onto a table, or look at at hour glass running out, you see the same shape. What's going on?

It's a combination of gravity and friction. The grains of sand, rock or ash are pulled down by gravity; they want to flow down-hill. They are, however, also gripped by the other particles already on the slope. This gripping is called friction. Sharp, rough or sticky substances have more friction and this grip force is strong. Smooth or slippery substances are gripped less.

[Image: math.png][/size]

The friction force is proportional to the normal reaction (the force perpendicular to the direction the object is trying to move), and the limiting ratio of this force to the normal is a dimensionless constant called the coefficient of friction. This is typically given the symbol [size=undefined]μ[/size]

As you can see from the diagram above there is a relationship between the angle of the slope the coefficient of friction. When a particle is dropped onto a slope, if the angle is below a critical angle, it will stay put. If the angle is steeper than a critical angle (defined by the inverse tangent of the coefficient of friction), then it cannot grip and slides down the slope.

It is this behaviour (applied rotationally symmetrically) over the pile that creates the cone shape, and the steepness of the cone is proportional to the coefficient of friction.

[Image: cone.png][/size]

Engineers call this angle the Angle of Repose

The study of friction and the relationship between surfaces moving relative to each other is called Tribology. If you look around, you'll find many examples of the phenomenon.

[Image: hybrid.jpg]Images: Ernie Reyesjamiesrabbits
Angles of Repose[/size]

Here are some sample materials and their angles of repose.

Dry gravel
Dry sand
Wet sand

Great Pit of Carkoon[/size]

Fans of Star Wars* will know that the same forces can be applied to an inverted version of the shape. Rather the defining a conical protrusion, the same physics principles can define a conical depression, the slope of which is at the same critical angle.

[Image: pit.png][/size]

Maybe you've experienced this as a child when digging a hole at the beach? As you dig deeper you find that you have to make the diameter of the hole increasingly larger as the sides of the hole continue to collapse. There is a critical angle (which we now know is the Angle of Repose), after which, the walls are no longer able to support the particles and they slide inwards. Wet sand has a higher coefficient of friction than dry sand, so it is possible to dig steeper sided holes in the wet.

There are some clever animals that use this principle to their advantage to catch pray. On of these is the antlion. The antlion larva creates a conical depression in dry sand, and hides at the bottom.

The angle of the sides of the depression are at the angle of repose. An unsuspecting walking insect, such as an ant, when it encounters the slope will slide down into the bottom of the pit; not being able to gain traction to pull itself out, as each attempt to climb up the slope loosens particles the are critically balanced and sends all sliding down to the bottom of the pit and into the waiting jaws of the antlion.

[Image: antlion.jpg][/size]

“You will, therefore, be taken to the Dune Sea and cast into the Pit of Carkoon, the nesting place of the all powerful Sarlacc.”
— C-3PO's translation of Jabba the Hutt's words to Han Solo, Luke Skywalker, and Chewbacca.


(04-21-2015, 01:53 AM)EA Wrote: Recall:

Land NOT Land

Not Lando  Naughty [Image: rsz_soloandcalrissian-0000.jpg]

[Image: 271F05AA00000578-3017232-image-a-20_1427670839417.jpg]

When the sun enters the scene things may or may not change.
depends on pov. That was my first post after post #5050

[Image: 265E408F00000578-2982450-image-m-6_1425638770771.jpg]

Not Land.

[Image: nintchdbpict000301919835.jpg?strip=all&w=960]

Harrison Ford's near miss: video shows moment actor flies over ... › News

  1. [url=]
2 days ago - Harrison Ford's near miss: video shows moment actor flies over passenger plane. Video shows Harrison Ford wrongly flying over airliner Watch | Video shows Harrison Ford wrongly flying over airliner. 00:28 ... 22 February 2017 • 6:52am ... The Federal Aviation Administration is investigating the incident.[/size]
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
Rosetta comet orbiter films deep-space landslide
March 21, 2017

[Image: 58d156fdacfea.jpg]
OSIRIS NAC image of the Aswan new edge taken on 18 May 2016 at 8.40 km far from the 67P nucleus. The spatial scale of the image is 12 cm/pixel. The white arrows show the new sharp edge after the collapse. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Landslides are not unique to Earth, researchers revealed on Tuesday.

In 2015, Europe's Rosetta spacecraft witnessed—and photographed—a big one on the surface of a comet in deep, dark space, they reported in the journal Nature Astronomy.
The cliffside collapse created about 2,000 tonnes of rubble, 99 percent of which settled at the foot of the precipice.
The rest was ejected in a spectacular jet of dust.
In the first direct evidence for cometary landslides, Rosetta captured before and after images of a wall giving way along a crack 70 metres (230 feet) long and one metre wide on the edge of a cliff named Aswan.
Scientists were alerted to the possible collapse in July 2015 by a large plume of dust ejected from comet 67P/Churyumov-Gerasimenko, which Rosetta was orbiting at the time.
They traced the jet's origins to Aswan.
Five days later, the orbiter's OSIRIS camera observed a "fresh, sharp and bright" edge on the Aswan cliff, where the fracture had been before.
The spot—six times brighter than the comet's usual, dusty surface—was the newly-exposed, pristine, icy insides of the comet.

Video representation of the illumination conditions at the Aswan cliff and plateau on 10 July 2015. Credit: M. Pajola et al.
The Rosetta mission had observed several previous outbursts, and hypothesised they may be the result of collapsing cliffs.
But the study documents "the first unambiguous link between an outburst and a cliff collapse on a comet," the team wrote.
Launched in 2004, the European Space Agency's Rosetta spacecraft travelled more than six billion kilometres to reach comet 67P some 400 million kilometres (250 million miles) from Earth.
[Image: 58d1571880ba2.jpg]
OSIRIS NAC image of the Aswan cliff taken on 26 December 2015 at 77.05 km far from the 67P nucleus. The spatial scale of the image is 1.41 m/pixel. The white arrow shows the bright Aswan cliff with the water ice exposed. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
In November 2014, Rosetta released a tiny robot named Philae onto the comet's surface to further probe the alien body.
The pair's mission was to unravel the mysteries of life by investigating the comet from all angles.
Billions of comets travelling in elliptic orbits around the Sun are believed to be leftovers from the birth of our planetary system some 4.6 billion years ago.
[Image: 58d1572de1ee6.jpg]
NavCam image taken on 10 July 2015 at 156.58 km far from the 67P nucleus. The spatial scale of the image is 15.81 m/pixel. The white arrow shows the outburst caused by the Aswan cliff collapse (in shadow here). Credit: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0
On 67P, the Rosetta mission uncovered organic molecules, the building blocks of life.
This supported the theory that comets helped spark life on Earth by delivering organic materials when they slammed into our young planet.
Water, on the other hand, was unlikely to have come from comets of 67P's type, the mission concluded.
[Image: 58d1574158553.jpg]
OSIRIS NAC image of the Aswan cliff taken on 21 September 2014 at 27.61 km far from the 67P nucleus. The spatial scale of the image is 0.48 m/pixel. The white arrow shows the 70 m long, 1 m wide fracture at the edge of the cliff. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
[Image: 1x1.gif] Explore further: Image: Rosetta's shadow crosses Comet 67P/Churyumov–Gerasimenko in daring encounter
More information: The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse, Nature 

Read more at:[/url]

Before and after: Unique changes spotted on comet 67p/Churyumov-Gerasimenko

March 21, 2017

[Image: beforeandaft.jpg]
Several sites of cliff collapse on Comet 67P/Churyumov-Gerasimenko were identified during Rosetta's mission. This image focuses on an example in the Ash region, close to the boundary with Imhotep on the comet's large lobe. The yellow arrows mark the fractures where the detachment occurred. The images were taken by Rosetta's OSIRIS camera on Dec. 2, 2014 (left) and March 12, 2016 (right). Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
A study published March 21, 2017 in the journal Science summarizes the types of surface changes observed during the two years that the European Space Agency's Rosetta spacecraft spent investigating comet 67P/Churyumov-Gerasimenko. Notable differences are seen before and after the comet's most active period—perihelion—when it reached its closest point to the Sun along its orbit.

"Monitoring the comet continuously as it traversed the inner solar system gave us an unprecedented insight not only into how comets change when they travel close to the Sun, but also how fast these changes take place," said Mohamed El-Maarry, a comet researcher at the University of Colorado, Boulder and the lead author of the study.
The changes are linked to different geological processes: weathering and erosion, sublimation of water ice, and mechanical stresses arising from the comet's spin.
"Comet landscapes are fascinating. They are sculpted by slow erosion and dramatic outbursts," said Dennis Bodewits, an assistant research scientist in astronomy at the University of Maryland who is a co-author of the study. "One of the key points of this paper is that the observed changes are small and relatively subtle. Features such as large holes suggest that more violent activity is infrequent on the time scale of an orbital period."
Weathering occurs all over the comet, where consolidated materials are weakened—such as by heating and cooling cycles on daily or seasonal timescales—causing their fragmentation. Combined with heating of subsurface ices that lead to outflows of gas, this can ultimately result in the sudden collapse of cliff walls, the evidence of which is apparent in several locations on the comet.
[Image: 1-beforeandaft.jpg]
A 30-meter-wide, 12,800-ton boulder was found to have moved 140 meters in the Khonsu region of Comet 67P/Churyumov-Gerasimenko in the lead up to perihelion in August 2015, when the comet's activity was at its highest. In both images, an arrow points to the boulder; in the right-hand image, the dotted circle outlines the original location of the boulder for reference. The images were taken by Rosetta's OSIRIS camera on May 2, 2015 (left) and Feb. 7, 2016 (right). Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
A completely different process is thought to be responsible for a 500-meter-long fracture spotted in August 2014 that runs through the comet's neck in the Anuket region. This fracture was found to have extended by about 30 meters by December 2014. This is linked to the comet's increasing spin rate in the lead up to perihelion. Furthermore, in images taken in June 2016, a new 150 to 300-meter-long fracture was identified parallel to the original fracture.
Close to the fractures, a four-meter-wide boulder moved by about 15 meters, as determined by comparing images taken in March 2015 and June 2016. It is not clear whether the fracture extension and movement of the boulder are related to each other or caused by different processes.
A substantially larger boulder, some 30 meters wide and weighing 12,800 tons, was found to have moved an impressive 140 meters in the Khonsu region, on the larger of the two comet lobes.

It is thought that the boulder moved during the perihelion period, as several outburst events were detected close to its original position. The movement could have been triggered in one of two ways: either a large amount of underlying material eroded away, allowing the boulder to roll downslope, or a forceful outburst could have directly lifted the boulder to the new location.
Erosion caused by the sublimation of material, and deposition of dust falling from outbursts, are also thought to be responsible for sculpting the landscape in different ways. For example, scarps in several smooth plains have been observed to retreat by tens of meters and at a rate of up to a few meters per day around perihelion.
[Image: 2-beforeandaft.jpg]
Dune-like features that were identified early in Rosetta’s mission in the neck region of Comet 67P/Churyumov–Gerasimenko were seen to evolve over the two years of study (first and last images). In addition, numerous circular scarp-like features were seen to develop and fade over time (central set of images). The circular features reached a diameter of 100 m in less than three months before subsequently fading away again, giving rise to a new set of ripples. The repeated development of these unique features at the same spot is thought to be linked to the curved structure of the neck region directing the flow of sublimating gas in a particular way.  The arrows point to the approximately location of the ripple and scarp features to help guide the eye between images when the viewing orientation and resolution changes. The images were taken by Rosetta’s OSIRIS camera on 5 September 2014 (left), 25 April 2015 (centre top left), 10 May 2015 (centre top right), 11 July 2015 (centre bottom left), 20 December 2015 (centre bottom right), and 7 June 2016 (right). The image resolutions are 0.8, 1.6, 2.4, 2.9, 1.7 and 0.5 m/pixel, respectively. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
"Scarp retreats were observed before on Comet Tempel 1, inferred by comparing images taken during flybys of the comet by NASA's Deep Impact in 2005, and Stardust-NExT in 2011," said El-Maarry. "What we were able to do with Rosetta was to monitor similar changes continuously, and at a higher resolution. Our observations additionally tell us that scarp retreat seems to be a common process on comets, specifically in smooth-looking deposits."
Furthermore, in the smooth plains of the Imhotep region, previously hidden circular features and small boulders have been exposed by the removal of material. In one location, a depth of about three meters had been removed, most likely through the sublimation of underlying ices.
Changes were also noted in the comet's smooth neck region, near distinctive ripples that were likened to Earth's sand dunes when they were first identified. Close monitoring of the ripple formations showed this location to also display expanding circular features in the soft material that reached diameters of 100 meters in less than three months. They subsequently faded away to give rise to new sets of ripples.
The researchers speculate that the repeated development of these unique features at the same spot must be linked to the curved structure of the neck region directing the flow of sublimating gas in a particular way.
Another type of change is the development of honeycomb-like features noticed in the dusty terrains of the Ma'at region on the comet's small lobe in the northern hemisphere, marked by an increase in surface roughness in the six months leading up to perihelion.
[Image: 3-beforeandaft.jpg]
Showcase of the different types of changes identified in high-resolution images of Comet 67P/Churyumov–Gerasimenko during more than two years of monitoring by ESA’s Rosetta spacecraft. The approximate locations of each feature are marked on the central context images. Dates of when the ‘before’ and ‘after’ images were taken are also indicated. Note that the orientation and resolution between image pairs may vary, therefore in each image set arrows point to the location of the changes, for guidance.  Credit: Top centre images: ESA/Rosetta/NAVCAM, CC BY-SA 3.0 IGO; all others: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Similar to other seasonal changes, these features faded substantially after perihelion, presumably as a result of resurfacing by the deposition of new particles ejected from the southern hemisphere during this active period.
"This documentation of changes over time was a key goal of Rosetta's mission, and shows the surface of comets as geologically active, on both seasonal and short transient timescales," said Matt Taylor, Rosetta project scientist for the European Space Agency.
The scientists also note that although many small-scale localized changes have occurred, there were no major shape-changing events that significantly altered the comet's overall appearance. Ground-based observations over the last few decades suggest similar levels of activity during each perihelion, so the researchers think that the major landforms seen during Rosetta's mission were sculpted during a different orbital configuration.
"At UMD, we use telescopes such as Swift and Spitzer to look at the activity of comets as they approach the Sun for the first time," said Michael A'Hearn, a Distinguished University Professor Emeritus of astronomy at UMD and a co-author on the study. A'Hearn also served as principal investigator on the Deep Impact mission. "We know that such comets are indeed very active. But Rosetta allowed us to see in great detail what this activity did to the surface of comet 67P/Churyumov-Gerasimenko."
The research paper, "Surface changes on comet 67P/Churyumov-Gerasimenko suggest a more active past," Mohamed El-Maarry et al., was published March 21, 2017 in the journal Science.
A complementary paper, "The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse," by M. Pajola et al, is also published today in Nature Astronomy. Read our news story here.
[Image: 1x1.gif] Explore further: Rosetta comet orbiter films deep-space landslide
More information: "Surface changes on comet 67P/Churyumov-Gerasimenko suggest a more active past,", ScienceDOI: 10.1126/science.aak9384 

Read more at:[url=]
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
well that is certainly fascinating that a 12000 pound boulder would move that far {140 meters}
at perihelion

Quote:For example, 
scarps in several smooth plains have been observed to retreat by tens of meters 
and at a rate of up to a few meters per day around perihelion.

or a forceful outburst Whip  could have directly lifted the boulder to the new location.


and just before and after perihelion --- we see a consistency of CME's from the sun,
in almost all passing comets,
as evidenced by Encke just recently during a long period of solar inactivity.
Quote:or a forceful outburst [Image: whip.gif]  could have directly lifted the boulder to the new location.
well that is certainly fascinating that a 12000 pound boulder would move that far {140 meters}
at perihelion

A 140m Boulder Dash?  Cry

[Image: post-3824821-0-38707800-1381197341.jpg]

Philae is as Heisenberg was
Scientists evade the Heisenberg uncertainty principle

March 22, 2017
Land   Sheep  Not
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
Chemical engineers explain oxygen mystery on comets
May 8, 2017

[Image: caltechchemi.jpg]
Caltech's Konstantinos Giapis has shown how molecular oxygen may be produced on the surface of comets using lab experiments. He and his postdoctoral scholar Yunxi Yao fired high-speed water molecules at oxidized silicon and iron surfaces and observed the production of a plume that included molecular oxygen. Giapis says that similar conditions exist on the comet 67P/Churyumov-Gerasimenko, where the European Space Agency's Rosetta mission detected molecular oxygen. Credit: Caltech
A Caltech chemical engineer who normally develops new ways to fabricate microprocessors in computers has figured out how to explain a nagging mystery in space—why comets expel oxygen gas, the same gas we humans breathe.

The discovery that comets produce oxygen gas—also referred to as molecular oxygen or O2—was announced in 2015 by researchers studying the comet 67P/Churyumov-Gerasimenko with the European Space Agency's Rosetta spacecraft. The mission unexpectedly found abundant levels of molecular oxygen in the comet's atmosphere. Molecular oxygen in space is highly unstable, as oxygen prefers to pair up with hydrogen to make water, or carbon to make carbon dioxide. Indeed, O2 has only been detected twice before in space in star-forming nebulas.
Scientists have proposed that the molecular oxygen on comet 67P/Churyumov-Gerasimenko might have thawed from its surface after having been frozen inside the comet since the dawn of the solar system 4.6 billion years ago. But questions persist because some scientists say the oxygen should have reacted with other chemicals over all that time.
A professor of chemical engineering at Caltech, Konstantinos P. Giapis, began looking at the Rosetta data because the chemical reactions happening on the comet's surface were similar to those he has been performing in the lab for the past 20 years. Giapis studies chemical reactions involving high-speed charged atoms, or ions, colliding with semiconductor surfaces as a means to create faster computer chips and larger digital memories for computers and phones.
"I started to take an interest in space and was looking for places where ions would be accelerated against surfaces," says Giapis. "After looking at measurements made on Rosetta's comet, in particular regarding the energies of the water molecules hitting the comet, it all clicked. What I've been studying for years is happening right here on this comet."
In a new Nature Communications study, Giapis and his co-author, postdoctoral scholar Yunxi Yao, demonstrate in the lab how the comet could be producing oxygen. Basically, water vapor molecules stream off the comet as the cosmic body is heated by the sun. The water molecules become ionized, or charged, by ultraviolet light from the sun, and then the sun's wind blows the ionized water molecules back toward the comet. When the water molecules hit the comet's surface, which contains oxygen bound in materials such as rust and sand, the molecules pick up another oxygen atom from these surfaces and O2 is formed.
In other words, the new research implies that the molecular oxygen found by Rosetta need not be primordial after all but may be produced in real time on the comet.
"We have shown experimentally that it is possible to form molecular oxygen dynamically on the surface of materials similar to those found on the comet," says Yao.
"We had no idea when we built our laboratory setups that they would end up applying to the astrophysics of comets," says Giapis. "This original chemistry mechanism is based on the seldom-considered class of Eley-Rideal reactions, which occur when fast-moving molecules, water in this case, collide with surfaces and extract atoms residing there, forming new molecules. All necessary conditions for such reactions exist on comet 67P."
Other astrophysical bodies, such as planets beyond our solar system, or exoplanets, might also produce molecular oxygen with a similar "abiotic" mechanism—without the need for life. This may influence how researchers search for signs of life on exoplanets in the future.
"Oxygen is an important molecule, which is very elusive in interstellar space," says astronomer Paul Goldsmith of JPL, which is managed by Caltech for NASA. Goldsmith is the NASA project scientist for the European Space Agency's Herschel mission, which made the first confirmed detection of molecular oxygen in space in 2011. "This production mechanism studied in Professor Giapis's laboratory could be operating in a range of environments and shows the important connection between laboratory studies and astrochemistry."
The Nature Communications paper is titled "Dynamic molecular oxygen production in cometary comae."
[Image: 1x1.gif] Explore further: Rosetta finds molecular oxygen on comet 67P (Update)
Journal reference: Nature Communications [Image: img-dot.gif] [Image: img-dot.gif]
Provided by: California Institute of Technology

Read more at:[/url][url=]
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
That is very interesting indeed.

Quote:"This original chemistry mechanism 
is based on the seldom-considered class of Eley-Rideal reactions,
which occur when fast-moving molecules, 
water in this case,
collide with surfaces and extract atoms residing there, forming new molecules. 
All necessary conditions for such reactions exist on comet 67P."

Those reactions also create H2
Formation of Astrobiologically Important Molecules in Extraterrestrial Environments

[Image: k-figure3.jpg]
Rosetta finds comet connection to Earth's atmosphere
by Staff Writers
Paris (ESA) Jun 12, 2017

[Image: comet-rosetta-67p-churyumov-gerasimenko-lg.jpg]
As a result of the observations, ROSINA identified seven isotopes of xenon, as well as several isotopes of another noble gas, krypton; these brought to three the inventory of noble gases found at Rosetta's comet, following the discovery of argon from measurements performed in late 2014.

The challenging detection, by ESA's Rosetta mission, of several isotopes of the noble gas xenon at Comet 67P/Churyumov-Gerasimenko has established the first quantitative link between comets and the atmosphere of Earth. The blend of xenon found at the comet closely resembles U-xenon, the primordial mixture that scientists believe was brought to Earth during the early stages of Solar System formation.
These measurements suggest that comets contributed about one fifth the amount of xenon in Earth's ancient atmosphere. Xenon - a colourless, odourless gas which makes up less than one billionth of the volume of Earth's atmosphere - might hold the key to answer a long-standing question about comets: did they contribute to the delivery of material to our planet when the Solar System was taking shape, some 4.6 billion years ago? And if so, by how much?
The noble gas xenon is formed in a variety of stellar processes, from the late phases of low- and intermediate-mass stars to supernova explosions and even neutron star mergers. Each of these phenomena gives rise to different isotopes of the element. As a noble gas, xenon does not interact with other chemical species, and is therefore an important tracer of the material from which the Sun and planets originated, which in turns derives from earlier generations of stars.
"Xenon is the heaviest stable noble gas and perhaps the most important because of its many isotopes that originate in different stellar processes: each one provides an additional piece of information about our cosmic origins," says Bernard Marty from CRPG-CNRS and Universite de Lorraine, France. Bernard is the lead author of a paper reporting Rosetta's discovery of xenon at Comet 67P/C-G, which is published in Science.
It is because of this special 'fingerprint' that scientists have been using xenon to investigate the composition of the early Solar System, which provides important clues to constrain its formation. Over the past decades, they sampled the relative abundances of its various isotopes at different locations: in the atmosphere of Earth and Mars, in meteorites deriving from asteroids, at Jupiter, and in the solar wind - the flow of charged particles streaming from the Sun.
The blend of xenon present in the atmosphere of our planet contains a higher abundance of heavier isotopes with respect to the lighter ones; however, this is a result of lighter elements escaping more easily from Earth's gravitational pull and being lost to space in greater amounts. By correcting the atmospheric composition of xenon for this runaway effect, scientists in the 1970s calculated the composition of the primordial mixture of this noble gas, known as U-xenon, that was once present on Earth.
This U-xenon contained a similar mix of light isotopes to that of asteroids and the solar wind, but included significantly smaller amounts of the heavier isotopes.
"For these reasons, we have long suspected that xenon in the early atmosphere of Earth could have a different origin from the average blend of this noble gas found in the Solar System," says Bernard.
One of the explanations is that Solar System xenon derives directly from the protosolar cloud, a mass of gas and dust that gave rise to the Sun and planets, while the xenon found in the Earth's atmosphere was delivered at a later stage by comets, which in turn might have formed from a different mix of material.
With ESA's Rosetta mission visiting Comet 67P/Churyumov-Gerasimenko, an icy fossil of the early Solar System, scientists could finally gather the long-sought data to test this hypothesis.
"Searching for xenon at the comet was one of the most crucial and challenging measurements we performed with Rosetta," says Kathrin Altwegg from the University of Bern, Switzerland, principal investigator of ROSINA, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, which was used for this study.
Xenon is very diffuse in the comet's thin atmosphere, so the navigation team had to fly Rosetta very close - 5 km to 8 km from the surface of the nucleus - for a period of three weeks so that ROSINA could obtain a significant detection of all the relevant isotopes.
Flying so close to the comet was extremely challenging because of the large amount of dust that was lifting off the surface at the time, which could confuse the star trackers that were used to orient the spacecraft.
Eventually, the Rosetta team decided to perform this operation in the second half of May 2016. This period was chosen as a compromise so that enough time would have passed after the comet's perihelion, in August 2015, for the dust activity to be less intense, but not too much for the atmosphere to be excessively thin and the presence of xenon hard to detect.
As a result of the observations, ROSINA identified seven isotopes of xenon, as well as several isotopes of another noble gas, krypton; these brought to three the inventory of noble gases found at Rosetta's comet, following the discovery of argon from measurements performed in late 2014.
"These measurements required a long stretch of dedicated time solely for ROSINA, and it would have been very disappointing if we hadn't detected xenon at Comet 67P/C-G, so I'm really glad that we succeeded in detecting so many isotopes," adds Kathrin.
Further analysis of the data revealed that the blend of xenon at Comet 67P/C-G, which contains larger amounts of light isotopes than heavy ones, is quite different from the average mixture found in the Solar System. A comparison with the on-board calibration sample confirmed that the xenon detected at the comet is also different from the current mix in the Earth's atmosphere.
Along the vines of the Vineyard.
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Does the organic material of comets predate our solar system?
September 6, 2017

[Image: doestheorgan.jpg]
The nucleus of comet 67P Churyumov-Gerasimenko (“Chury") as seen by the European Rosetta space probe. Credit: © ESA / Rosetta / MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
The Rosetta space probe discovered a large amount of organic material in the nucleus of comet 'Chury.' In an article published by MNRAS on Aug. 31, 2017, two French researchers advance the theory that this matter has its origin in interstellar space and predates the birth of the solar system.

The ESA's Rosetta mission, which ended in September 2016, found that organic matter made up 40% (by mass) of the nucleus of comet 67P Churyumov-Gerasimenko, a.k.a. Chury. Organic compounds, combining carbon, hydrogen, nitrogen, and oxygen, are building blocks of life on Earth. Yet, according to Jean-Loup Bertaux and Rosine Lallement—from the Laboratoire Atmosphères, Milieux, Observations Spatiales (CNRS / UPMC / Université de Versailles Saint-Quentin-en-Yvelines) and the Galaxies, Étoiles, Physique et Instrumentation department of the Paris Observatory (Observatoire de Paris / CNRS / Université Paris Diderot), respectively—these organic molecules were produced in interstellar space, well before the formation of the Solar System. Bertaux and Lallement further assert that astronomers are already familiar with much of this matter.
For 70 years, scientists have known that analysis of stellar spectra indicates unknown absorptions, throughout interstellar space, at specific wavelengths called the diffuse interstellar bands (DIBs). DIBs are attributed to complex organic molecules that US astrophysicist Theodore Snow believes may constitute the largest known reservoir of organic matter in the Universe. This interstellar organic material is usually found in the same proportions. However, very dense clouds of matter like presolar nebulae are exceptions. In the middle of these nebulae, where matter is even denser, DIB absorptions plateau or even drop. This is because the organic molecules responsible for DIBs clump together there. The clumped matter absorbs less radiation than when it floated freely in space.
Such primitive nebulae end up contracting to form a solar system like our own, with planets . . . and comets. The Rosetta mission taught us that comet nuclei form by gentle accretion of grains progressively greater in size. First, small particles stick together into larger grains. These in turn combine into larger chunks, and so on, until they form a comet nucleus a few kilometers wide.
Thus, the organic molecules that formerly populated the primitive nebulae—and that are responsible for DIBs—were probably not destroyed, but instead incorporated into the grains making up cometary nuclei. And there they have remained for 4.6 billion years. A sample-return mission would allow laboratory analysis of cometary organic material and finally reveal the identity of the mysterious interstellar matter underlying observed absorption lines in stellar spectra.
If cometary organic molecules were indeed produced in interstellar space—and if they played a role in the emergence of life on our planet, as scientists believe today—might they not also have seeded life on many other planets of our galaxy?
[Image: 1x1.gif] Explore further: Rosetta catches dusty organics
More information: Jean-Loup Bertaux et al, Diffuse Interstellar Bands carriers and cometary organic material., Monthly Notices of the Royal Astronomical Society (2017). DOI: 10.1093/mnras/stx2231 
Journal reference: Monthly Notices of the Royal Astronomical Society[Image: img-dot.gif] [Image: img-dot.gif]
Provided by: CNRS

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With a forked tongue the snake singsss...
Unique type of object discovered in our solar system

September 20, 2017

[Image: 170920144724_1_900x600.jpg]
This artist's impression shows the binary asteroid 288P, located in the main asteroid belt between the planets Mars and Jupiter. The object is unique as it is a binary asteroid which also behaves like a comet. The comet-like properties are the result of water sublimation, caused by the heat of the Sun. The orbit of the asteroids is marked by a blue ellipse.

[i]Credit: ESA/Hubble, L. Calçada[/i]

[i]With the help of the NASA/ESA Hubble Space Telescope, a German-led group of astronomers have observed the intriguing characteristics of an unusual type of object in the asteroid belt between Mars and Jupiter: two asteroids orbiting each other and exhibiting comet-like features, including a bright coma and a long tail. This is the first known binary asteroid also classified as a comet. The research is presented in a paper published in the journal [i]Nature today.
In September 2016, just before the asteroid 288P made its closest approach to the Sun, it was close enough to Earth to allow astronomers a detailed look at it using the NASA/ESA Hubble Space Telescope [1].
The images of 288P, which is located in the asteroid belt between Mars and Jupiter, revealed that it was actually not a single object, but two asteroids of almost the same mass and size, orbiting each other at a distance of about 100 kilometres. That discovery was in itself an important find; because they orbit each other, the masses of the objects in such systems can be measured.
But the observations also revealed ongoing activity in the binary system. "We detected strong indications of the sublimation of water ice due to the increased solar heating -- similar to how the tail of a comet is created," explains Jessica Agarwal (Max Planck Institute for Solar System Research, Germany), the team leader and main author of the research paper. This makes 288P the first known binary asteroid that is also classified as a main-belt comet.
Understanding the origin and evolution of main-belt comets -- comets that orbit amongst the numerous asteroids between Mars and Jupiter -- is a crucial element in our understanding of the formation and evolution of the whole Solar System. Among the questions main-belt comets can help to answer is how water came to Earth [2]. Since only a few objects of this type are known, 288P presents itself as an extremely important system for future studies.
The various features of 288P -- wide separation of the two components, near-equal component size, high eccentricity and comet-like activity -- also make it unique among the few known wide asteroid binaries in the Solar System. The observed activity of 288P also reveals information about its past, notes Agarwal: "Surface ice cannot survive in the asteroid belt for the age of the Solar System but can be protected for billions of years by a refractory dust mantle, only a few metres thick."
From this, the team concluded that 288P has existed as a binary system for only about 5000 years. Agarwal elaborates on the formation scenario: "The most probable formation scenario of 288P is a breakup due to fast rotation. After that, the two fragments may have been moved further apart by sublimation torques."
The fact that 288P is so different from all other known binary asteroids raises some questions about whether it is not just a coincidence that it presents such unique properties. As finding 288P included a lot of luck, it is likely to remain the only example of its kind for a long time. "We need more theoretical and observational work, as well as more objects similar to 288P, to find an answer to this question," concludes Agarwal.

[1] Like any object orbiting the Sun, 288P travels along an elliptical path, bringing it closer and further away to the Sun during the course of one orbit.
[2] Current research indicates that water came to Earth not via comets, as long thought, but via icy asteroids.

ESA/Hubble Information Centre. "Unique type of object discovered in our solar system." ScienceDaily. ScienceDaily, 20 September 2017. <>.
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Unexpected surprise: A final image from Rosetta
September 28, 2017

[Image: unexpectedsu.jpg]
A final image from Rosetta, shortly before it made a controlled impact onto Comet 67P/Churyumov–Gerasimenko on 30 September 2016, was reconstructed from residual telemetry. The image has a scale of 2 mm/pixel and measures about 1 m across. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Scientists analysing the final telemetry sent by Rosetta immediately before it shut down on the surface of the comet last year have reconstructed one last image of its touchdown site.

After more than 12 years in space, and two years following Comet 67P/Churyumov–Gerasimenko as they orbited the Sun, Rosetta's historic mission concluded on 30 September with the spacecraft descending onto the comet in a region hosting several ancient pits.
It returned a wealth of detailed images and scientific data on the comet's gas, dust and plasma as it drew closer to the surface.
But there was one last surprise in store for the camera team, who managed to reconstruct the final telemetry packets into a sharp image.
"The last complete image transmitted from Rosetta was the final one that we saw arriving back on Earth in one piece moments before the touchdown at Sais," says Holger Sierks, principal investigator for the OSIRIS camera at the Max Planck Institute for Solar System Research in Göttingen, Germany.
"Later, we found a few telemetry packets on our server and thought, wow, that could be another image."
During operations, images were split into telemetry packets aboard Rosetta before they were transmitted to Earth. In the case of the last images taken before touchdown, the image data, corresponding to 23 048 bytes per image, were split into six packets.
[Image: 1-unexpectedsu.jpg]
Annotated image indicating the approximate locations of some of Rosetta’s final images. Note that due to differences in timing and viewing geometry between consecutive images in this graphic, the illumination and shadows vary. Top left: a global view of Comet 67P/Churyumov–Gerasimenko shows the area in which Rosetta touched down in the Ma’at region on the smaller of the two comet lobes. This image  was taken by the OSIRIS narrow-angle camera on 5 August 2014 from a distance of 123 km. Top right: an image taken by the OSIRIS narrow-angle camera from an altitude of 5.7 km, during Rosetta’s descent on 30 September 2016. The image scale is about 11 cm/pixel and the image measures about 225 m across. The final touchdown point, named Sais, is seen in the bottom right of the image and is located within a shallow, ancient pit. Exposed, dust-free terrain is seen in the pit walls and cliff edges. Note the image is rotated 180º with respect to the global context image at top right. Middle: an OSIRIS wide-angle camera image taken from an altitude of about 331 m during Rosetta’s descent. The image scale is about 33 mm/pixel and the image measures about 55 m across. The image shows a mix of coarse and fine-grained material. Bottom right: the penultimate image, which was the last complete image taken and returned by Rosetta during its descent, from an altitude of 24.7±1.5 m. Bottom left: the final image, reconstructed after Rosetta’s landing, was taken at an altitude of 19.5±1.5 m. The image has a scale of 2 mm/pixel and measures about 1 m across. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
For the very last image the transmission was interrupted after three full packets were received, with 12 228 bytes received in total, or just over half of a complete image. This was not recognised as an image by the automatic processing software, but the engineers in Göttingen could make sense of these data fragments to reconstruct the image.
Owing to the onboard compression software, the data were not sent pixel-by-pixel but rather layer-by-layer, which gives an increasing level of detail with each layer.
The 53% of transmitted data therefore represents an image with an effective compression ratio of 1:38 compared to the anticipated compression ratio of 1:20, meaning some of the finer detail was lost.
That is, it gets a lot blurrier as you zoom in compared with a full-quality image. This can be likened to compressing an image to send via email, versus an uncompressed version that you would print out and hang on your wall.

The camera was not designed to be used below a few hundred metres from the surface but a sharper image could be achieved using the camera in a special configuration: while the camera was designed to be operated with a colour filter in the optical beam, this was removed for the last images. This would have resulted in the images being blurred for the normal imaging scenario above 300 m, but they came into focus at a 'sweet spot' of 15 m distance.
Approaching 15 m therefore improved the focus and thus level of detail, as can be seen in the reconstructed image taken from an altitude of 17.9–21.0 m and corresponding to a 1 x 1 m square region on the surface.
In the meantime, the altitude of the previously published last image has been revised to 23.3–26.2 m. The uncertainty arises from the exact method of altitude calculation and the comet shape model used.
The sequence of images progressively reveals more and more detail of the boulder-strewn surface, providing a lasting impression of Rosetta's touchdown site.
[Image: 1x1.gif] Explore further: Image: Rosetta's ever-changing view of a comet
Provided by: European Space Agency

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Quote:"Although it sounds very dramatic" Blum continues,


"it's actually a gentle process in which the dust agglomerates are not destroyed, but are combined into a larger body with an even greater gravitational attraction - the accumulation of the dust agglomerates into a coherent body is virtually the birth of the comet." Due to the relatively small mass of comet 67P, the pebbles survived intact until today, allowing scientists to confirm the hypothesis for the first time.

Quote: "Now all phases in the planet-formation model have been established", concludes Blum.

Comet mission reveals 'missing link' in our understanding of planet formation
October 25, 2017

[Image: 1-cometmission.jpg]
Schematic representation of the porous surface structure of comet 67P/Churyumov-Gerasimenko. Based on the results of the Rosetta mission, Blum and colleagues conclude that comet 67P is composed of millimetre-sized dust pebbles. It is assumed that the pebbles inside the comet consist of a mixture of dust and ice (light blue spheres in the image) and only the uppermost layers, which are exposed to direct sunlight, do not contain ice (dark grey spheres). Credit: Maya Krause, TU Braunschweig.
The missing link in our understanding of planet formation has been revealed by the first ever spacecraft to orbit and land on a comet, say German scientists. The study is published in a recent edition of the journal Monthly Notices of the Royal Astronomical Society.

A research team led by Jürgen Blum (Technische Universität Braunschweig, Germany) have analysed data from the historic Rosetta mission to uncover how comet 67P/Churyumov-Gerasimenko, or "Chury" for short, came into existence more than four and a half billion years ago.
Understanding the evolution of our solar system and its planets was one of the main objectives of the Rosetta mission to comet 67P/Churyumov-Gerasimenko. For Jürgen Blum and his international team it was worth it, because results from the various Rosetta and Philae instruments have revealed that only one out of many proposed models can explain their observations. Comet 67P consists of 'dust pebbles' ranging between millimetres and centimetres in size.
Professor Blum explains the implications of the team's observations "Our results show that only a single model for the formation of larger solid bodies in the young solar system may be considered for Chury. According to this formation model, 'dust pebbles' are concentrated so strongly by an instability in the solar nebula that their joint gravitational force ultimately leads to a collapse."
This process forms the missing link between the well-established formation of 'dust pebbles' ('planetary building blocks' formed in the solar nebula by sticking collisions between dust and ice particles) and the gravitational accretion of planetesimals into planets, which scientists have pondered over for years.
"Although it sounds very dramatic" Blum continues, "it's actually a gentle process in which the dust agglomerates are not destroyed, but are combined into a larger body with an even greater gravitational attraction - the accumulation of the dust agglomerates into a coherent body is virtually the birth of the comet." Due to the relatively small mass of comet 67P, the pebbles survived intact until today, allowing scientists to confirm the hypothesis for the first time.
In fact, the pebble-collapse formation model can explain many observed properties of comet 67P, for instance its high porosity and how much gas is escaping from inside. "Now all phases in the planet-formation model have been established", concludes Blum.
[Image: 1x1.gif] Explore further: Image: Rosetta's ever-changing view of a comet
More information: Jürgen Blum et al, Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles, Monthly Notices of the Royal Astronomical Society (2017). DOI: 10.1093/mnras/stx2741 
Journal reference: Monthly Notices of the Royal Astronomical Society[Image: img-dot.gif] [Image: img-dot.gif]
Provided by: Royal Astronomical Society

Read more at:[/url]

A Creation Tale:

[Image: 17151570652_5b283026f7_o.jpg]

Rosetta data have revealed an irregular 'duck shaped' 
comet with about 4.3 by 4.1 km in extent.
[Image: yyouareaduck.gif] (Detail in  D'tale of D'tail~3.33 km)
Unexpected surprise: A final faze from Rosetta
"Now all phases in the planet-formation model have been established", concludes Blum.

(07-28-2016, 01:36 AM)EA Wrote: Farewell Philae: Earth severs link with silent comet probe (Update)
July 27, 2016

[Image: 2-aphotoreleas.jpg]
A photo released by the European Space Agency (ESA) in November 2014 shows an image taken by Rosetta's lander Philae on the surface of Comet 67P/Churyumov-Gerasimenko
Earth bid a final farewell to robot lab Philae on Wednesday, severing communications after a year-long silence from the pioneering probe hurtling through space on a comet.

Writing an extraordinary chapter in space history, the washing machine-sized craft was the first to land on a comet—primeval rubble from the formation of the Solar System.
Philae sent home reams of data garnered from sniffing, tasting and prodding its new alien home hundreds of millions of kilometres (miles) from Earth.
Its plucky exploits captured the imagination of children, and many adults, who followed its successes and tribulations via Twitter and an animated cartoon series.
But after more than 12 months without news, it was decided to preserve all remaining energy available to Philae's orbiting mothership Rosetta, the European Space Agency (ESA) announced in a blog entitled: "Farewell, silent Philae".
Rosetta will remain in orbit around comet 67P/Churyumov-Gerasimenko for another two months.
It will crashland on September 30 to join Philae in their final resting place, concluding an historic quest for cometary clues to the origins of life on Earth.
"Today communication with Philae was stopped," Andreas Schuetz of German space agency DLR told AFP from ground control in Cologne on Wednesday.
"This is the end of a... fascinating and successful mission for the public and for science."
Part of a 1.3-billion-euro ($1.4-billion) ESA mission, Philae was launched into space in March 2004, riding piggyback on Rosetta.
The pair travelled some 6.5 billion km (four billion miles)—aided by gravity boosts from Earth and Mars—before entering 67P's orbit in August 2014.
Three months later, Rosetta sent the 100-kilogramme (220-pound) probe down to the comet surface—starting a nail-biting deep-space saga.
Philae's harpoons failed to fire into the comet surface, and it bounced several times.
Abandoning hope
The tiny robot ended up in a ditch shadowed from the Sun's battery-replenishing rays, but managed to run about 60 hours of experiments and send home valuable data before entering standby mode.
As 67P neared the Sun on its elongated orbit, Philae got a battery boost and emerged from hibernation in June 2015, sending a two-minute message via Rosetta, eliciting great excitement on Earth.
But after eight intermittent communications, the lander fell permanently silent on July 9, 2015.
Rosetta has continued to monitor the comet, but without catching sight of its long-lost charge, even from as close as 10 km away.
In February, ground controllers said they believed Philae was in eternal hibernation—though they opted to keep an ear open just in case.
Wednesday's final break, at 0900 GMT, means "abandoning all hope of receiving anything more from Philae," said Philippe Gaudon of France's CNES space agency.
"It's time for me to say goodbye," said Philae's Twitter account, announcing communications "will be switched off forever..."
As the comet moves further and further away from the Sun—some 520 million km by end July—Rosetta needs to save energy for her final weeks.
"We need to maximise the power available to Rosetta's scientific instruments, and thus had no choice but to turn off the ESS," ESA senior science advisor Mark McCaughrean told AFP.
The ESS is the Electrical Support System on board Rosetta, used to send home the results of Philae's science experiments and status reports.
"The power will only dwindle further, and so now the focus turns fully to Rosetta, whose amazingly succesful scientific mission will come to an end on 30 September," said McCaughrean.
"Everyone involved will be extremely sad, of course, but equally enormously proud of what has been achieved by this unique space mission."
Scientists will be busy for years analysing the data sent back by Philae and Rosetta.
Comets are deemed to be balls of primitive dust and ice left from the early years of the Solar System.
Their makeup interests scientists who speculate that comets may have seeded Earth—possibly other planets as well—with the ingredients for life.

Severs Linke like a Hatmehit! Freedom.
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[Image: 19296804119_40ec5a9ab1_o.png]

This thread was improv at itz best!  Rosetta will situate well and tale tell the rest of this comet's tail...

Quote: Wrote: "Now all phases in the planet-formation model have been established", concludes Blum.

Comet mission reveals 'missing link' in our understanding of planet formation
October 25, 2017

Holycowsmile  Improv is as gnosis was. LilD
RE: Rosetta stone"7 hours of terror" (7 days of Genesis)Philae approaches 67P/Churyumov-Gerasim...
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
Yesterday... Arrow

Scientists detect comets outside our solar system
October 26, 2017 by Jennifer Chu

[Image: 66-scientistsde.jpg]
An artist’s conception of a view from within the Exocomet system KIC 3542116. Credit: Danielle Futselaar
Scientists from MIT and other institutions, working closely with amateur astronomers, have spotted the dusty tails of six exocomets—comets outside our solar system—orbiting a faint star 800 light years from Earth.

These cosmic balls of ice and dust, which were about the size of Halley's Comet and traveled about 100,000 miles per hour before they ultimately vaporized, are some of the smallest objects yet found outside our own solar system.
The discovery marks the first time that an object as small as a comet has been detected using transit photometry, a technique by which astronomers observe a star's light for telltale dips in intensity. Such dips signal potential transits, or crossings of planets or other objects in front of a star, which momentarily block a small fraction of its light.
In the case of this new detection, the researchers were able to pick out the comet's tail, or trail of gas and dust, which blocked about one-tenth of 1 percent of the star's light as the comet streaked by.
"It's amazing that something several orders of magnitude smaller than the Earth can be detected just by the fact that it's emitting a lot of debris," says Saul Rappaport, professor emeritus of physics in MIT's Kavli Institute for Astrophysics and Space Research. "It's pretty impressive to be able to see something so small, so far away."
Rappaport and his team have published their results this week in the Monthly Notices of the Royal Astronomical Society. The paper's co-authors are Andrew Vanderburg of the Harvard-Smithsonian Center for Astrophysics; several amateur astronomers including Thomas Jacobs of Bellevue, Washington; and researchers from the University of Texas at Austin, NASA's Ames Research Center, and Northeastern University.
"Where few have traveled"
The detection was made using data from NASA's Kepler Space Telescope, a stellar observatory that was launched into space in 2009. For four years, the spacecraft monitored about 200,000 stars for dips in starlight caused by transiting exoplanets.
To date, the mission has identified and confirmed more than 2,400 exoplanets, mostly orbiting stars in the constellation Cygnus, with the help of automated doink-head that quickly sift through Kepler's data, looking for characteristic dips in starlight.

The smallest exoplanets detected thus far measure about one-third the size of the Earth. Comets, in comparison, span just several football fields, or a small city at their largest, making them incredibly difficult to spot.
However, on March 18, Jacobs, an amateur astronomer who has made it his hobby to comb through Kepler's data, was able to pick out several curious light patterns amid the noise.
Jacobs, who works as an employment consultant for people with intellectual disabilities by day, is a member of the Planet Hunters—a citizen scientist project first established by Yale University to enlist amateur astronomers in the search for exoplanets. Members were given access to Kepler's data in hopes that they might spot something of interest that a computer might miss.
In January, Jacobs set out to scan the entire four years of Kepler's data taken during the main mission, comprising over 200,000 stars, each with individual light curves, or graphs of light intensity tracked over time. Jacobs spent five months sifting by eye through the data, often before and after his day job, and through the weekends.
"Looking for objects of interest in the Kepler data requires patience, persistence, and perseverance," Jacobs says. "For me it is a form of treasure hunting, knowing that there is an interesting event waiting to be discovered. It is all about exploration and being on the hunt where few have traveled before."
"Something we've seen before"
Jacobs' goal was to look for anything out of the ordinary that computer doink-head may have passed over. In particular, he was searching for single transits—dips in starlight that happen only once, meaning they are not periodic like planets orbiting a star multiple times.
In his search, he spotted three such single transits around KIC 3542116, a faint star located 800 light years from Earth (the other three transits were found later by the team). He flagged the events and alerted Rappaport and Vanderburg, with whom he had collaborated in the past to interpret his findings.
"We sat on this for a month, because we didn't know what it was—planet transits don't look like this," Rappaport recalls. "Then it occurred to me that, 'Hey, these look like something we've seen before.'"
In a typical planetary transit, the resulting light curve resembles a "U," with a sharp dip, then an equally sharp rise, as a result of a planet first blocking a little, then a lot, then a little of the light as it moves across the star. However, the light curves that Jacobs identified appeared asymmetric, with a sharp dip, followed by a more gradual rise.
Rappaport realized that the asymmetry in the light curves resembled disintegrating planets, with long trails of debris that would continue to block a bit of light as the planet moves away from the star. However, such disintegrating planets orbit their star, transiting repeatedly. In contrast, Jacobs had observed no such periodic pattern in the transits he identified.
"We thought, the only kind of body that could do the same thing and not repeat is one that probably gets destroyed in the end," Rappaport says.
In other words, instead of orbiting around and around the star, the objects must have transited, then ultimately flown too close to the star, and vaporized.
"The only thing that fits the bill, and has a small enough mass to get destroyed, is a comet," Rappaport says.
The researchers calculated that each comet blocked about one-tenth of 1 percent of the star's light. To do this for several months before disappearing, the comet likely disintegrated entirely, creating a dust trail thick enough to block out that amount of starlight.
Vanderburg says the fact that these six exocomets appear to have transited very close to their star in the past four years raises some intriguing questions, the answers to which could reveal some truths about our own solar system.
"Why are there so many comets in the inner parts of these solar systems?" Vanderburg says. "Is this an extreme bombardment era in these systems? That was a really important part of our own solar system formation and may have brought water to Earth. Maybe studying exocomets and figuring out why they are found around this type of star … could give us some insight into how bombardment happens in other solar systems."
The researchers say that in the future, the MIT-led Transiting Exoplanet Survey Satellite (TESS) mission will continue the type of research done by Kepler.
Apart from contributing to the fields of astrophysics and astronomy, Rappaport says, the new detection speaks to the perserverence and discernment of citizen scientists.
"I could name 10 types of things these people have found in the Kepler data that doink-head could not find, because of the pattern-recognition capability in the human eye," Rappaport says. "You could now write a computer doink-headto find this kind of comet shape. But they were missed in earlier searches. They were deep enough but didn't have the right shape that was programmed into doink-head. I think it's fair to say this would never have been found by any algorithm."
This research made use of data collected by the Kepler mission, funded by the NASA Science Mission directorate.
[Image: 1x1.gif] Explore further: Finding a 'lost' planet, about the size of Neptune

Read more at:[/url]

Now... Arrow

"Although it sounds very dramatic" Blum continues, 

[Image:] ...

Astronomers capture first visiting object from outside our solar system

October 27, 2017

[Image: 59f3878953e34.jpg]
Credit: Queen's University Belfast
A Queen's University Belfast scientist is leading an international team in studying a new visitor to our solar system - the first known comet or asteroid to visit us from another star.

The fast-moving object, now named A/2017 U1, was initially spotted on 18 October in Hawaii by the Pan-STARRS 1 telescope in Hawaii. Professor Alan Fitzsimmons from the School of Mathematics and Physics at Queen's, together with colleagues in the UK, USA and Chile have been tracking it using powerful telescopes across the world.
Commenting on the project, Professor Fitzsimmons said: "By Wednesday this week it became almost certain this object was alien to our solar system. We immediately started studying it that night with the William Herschel Telescope in the Canary Islands, then on Thursday night with the Very Large Telescope in Chile."
The initial data implies it is a small rocky or icy object that may have been drifting through our galaxy for millions or even billions of years, before entering our solar system by chance. The object flew into the solar system from above, was close to the Sun last month, and is now already on its way back out to the stars.
Astronomers believe it was probably thrown out of another star system during a period of planet formation. The same process is thought to have unfolded 4.5 billion years ago around our own star, when Jupiter and Saturn formed. Despite suspecting such objects existed and looking out for them over past decades, scientists have never seen such an interstellar visitor until now.
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During rapid investigations, Professor Fitzsimmons' team has now captured clear images of the unusual object, and obtained data on its possible chemical makeup.
Meabh Hyland, a PhD student from the Astrophysics Research Centre at Queen's University Belfast, said: "It's wonderful and exciting to see this object passing through our planetary system."
Commenting on the incredible findings, Professor Fitzsimmons added: "It sends a shiver down the spine to look at this object and think it has come from another star."
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Credit: Queen's University Belfast
More information is needed to pin down the exact details of where the visitor came from and what its properties are, but luckily the object should be visible in powerful telescopes for a few more weeks, allowing scientists to continue their investigations.

The team studying the object include Professor Alan Fitzsimmons and Ms Meabh Hyland (Queen's University Belfast), Dr Colin Snodgrass (Open University), Dr Robert Jedicke (University of Hawaii) and Dr Bin Yang (European Southern Observatory).
[Image: 1x1.gif] Explore further: Small asteroid or comet 'visits' from beyond the solar system
Provided by: Queen's University Belfast

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Researchers present list of comet 67P/Churyumov-Gerasimenko ingredients
December 1, 2017, Max Planck Society

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Left: The surface of Rosetta’s comet. As the comet approaches the Sun, frozen gases evaporate from below the surface, dragging tiny particles of dust along with them. Right: These dust grains can be captured and examined using the COSIMA …more
The dust that comet 67P/Churyumov-Gerasimenko emits into space consists to about one half of organic molecules. The dust belongs to the most pristine and carbon-rich material known in our solar system and has hardly changed since its birth. These results of the COSIMA team are published today in the journal Monthly Notices of the Royal Astronomical Society. COSIMA is an instrument onboard the Rosetta spacecraft, which investigated comet 67P/Churyumov-Gerasimenko from August 2014 to September 2016. In their current study, the involved researchers including scientists from the Max Planck Institute for Solar System Research (MPS) analyze as comprehensively as ever before, what chemical elements constitute cometary dust.

When a comet traveling along it highly elliptical orbit approaches the Sun, it becomes active: frozen gases evaporate, dragging tiny dust grains into space. Capturing and examining these grains provides the opportunity to trace the "building materials" of the comet itself. So far, only few space missions have succeeded in this endeavor. These include ESA's Rosetta mission. Unlike their predecessors, for their current study the Rosetta researchers were able to collect and analyze dust particles of various sizes over a period of approximately two years. In comparison, earlier missions, such as Giotto's Flyby of comet 1P/Halley or Stardust, which even returned cometary dust from comet 81P/Wild 2 back to Earth, provided only a snapshot. In the case of the space probe Stardust, which raced past its comet in 2004, the dust had changed significantly during capture, so that a quantitative analysis was only possible to a limited extent.
In the course of the Rosetta mission, COSIMA collected more than 35000 dust grains. The smallest of them measured only 0.01 millimeters in diameter, the largest about one millimeter. The instrument makes it possible to first observe the individual dust grains with a microscope. In a second step, these grains are bombarded with a high-energy beam of indium ions. The secondary ions emitted in this way can then be "weighed" and analyzed in the COSIMA mass spectrometer. For the current study, the researchers limited themselves to 30 dust grains with properties that ensured a meaningful analysis. Their selection includes dust grains from all phases of the Rosetta mission and of all sizes.
"Our analyzes show that the composition of all these grains is very similar," MPS researcher Dr. Martin Hilchenbach, Principal Investigator of the COSIMA team, describes the results. The scientists conclude that the comet's dust consists of the same "ingredients" as the comet's nucleus and thus can be examined in its place.
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Left: Overview of the chemical elements that make up Rosetta’s comet. Right: Average mass distribution of organic and mineral substances in Rosetta’s comet. Credit: © ESA / Rosetta / MPS for COSIMA Team MPS / CSNSM / UNIBW / TUORLA / IWF / …more
As the study shows, organic molecules are among those ingredients at the top of the list. These account for about 45 percent of the weight of the solid cometary material. "Rosetta's comet thus belongs to the most carbon-rich bodies we know in the solar system," says MPS scientist and COSIMA team member Dr. Oliver Stenzel. The other part of the total weight, about 55 percent, is provided by mineral substances, mainly silicates. It is striking that they are almost exclusively non-hydrated minerals i.e. missing water compounds.

"Of course, Rosetta's comet contains water like any other comet, too," says Hilchenbach. "But because comets have spent most of their time at the icy rim of the solar system, it has almost always been frozen and could not react with the minerals." The researchers therefore regard the lack of hydrated minerals in the comet's dust as an indication that 67P contains very pristine material.
This conclusion is supported by the ratio of certain elements such as carbon to silicon. With more than 5, this value is very close to the Sun's value, which is thought to reflect the ratio found in the early solar system.
The current findings also touch on our ideas of how life on Earth came about. In a previous publication, the COSIMA team was able to show that the carbon found in Rosetta's comet is mainly in the form of large, organic macromolecules. Together with the current study, it becomes clear that these compounds make up a large part of the cometary material. Thus, if comets indeed supplied the early Earth with organic matter, as many researchers assume, it would probably have been mainly in the form of such macromolecules.
[Image: 1x1.gif] Explore further: Rosetta catches dusty organics
More information: Anaïs Bardyn et al. Carbon-rich dust in comet 67P/Churyumov-Gerasimenko measured by COSIMA/Rosetta, Monthly Notices of the Royal Astronomical Society (2017). DOI: 10.1093/mnras/stx2640

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NASA reveals finalists for next New Frontiers robotic mission: Saturn's moon Titan or Rosetta spacecraft's comet
December 21, 2017 by Amina Khan, Los Angeles Times

The field for NASA's next New Frontiers mission is narrowing. Officials announced the two finalists for a new robotic explorer mission—one that would send a spacecraft to bring samples of the comet 67P/Churyumov-Gerasimenko to Earth, and another to explore Saturn's moon Titan.
The two mission concepts, CAESAR and Dragonfly, detailed in a NASA briefing Wednesday, beat out 10 other proposals to explore solar system targets including a basin on the moon; the surface of Venus; and Enceladus, the icy ocean world that also circles Saturn.
"The New Frontiers program is really the premier program for our principal investigators and indeed it's one of the most difficult programs to be selected for," said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. NASA only selects about two of these medium-class missions every decade, he added.
The comet mission CAESAR (or Comet Astrobiology Exploration Sample Return) would send a spacecraft back to comet 67P, explored by the European Space Agency's Rosetta spacecraft and Philae lander in recent years. There, the craft would gather material from the nucleus of the comet and send it back to Earth for scientists to study in November 2038.
CAESAR is led by Steve Squyres of Cornell University, the principal investigator of NASA's Opportunity rover, which has been studying Mars since 2004. The mission will be managed by NASA's Goddard Space Flight Center; the sample return capsule will be provided by the Japanese space agency, JAXA, whose Hayabusa mission brought a similar capsule back from the asteroid Itokawa in 2010.
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The CAESAR (Comet Astrobiology Exploration SAmple Return) mission will acquire a sample from the nucleus of comet Churyumov-Gerasimenko, returning it safely to Earth. Comets are made up of materials from ancient stars, interstellar clouds, and the birth of our solar system. The CAESAR sample will reveal how these materials contributed to the early Earth, including the origins of the Earth's oceans, and of life. Credit: NASA
"Comets are among the most scientifically important objects in the solar system, but they're also among the most poorly understood," Squyres said.
Comets are the leftover building blocks of planets, and as such could reveal much about the solar system's early development. They also are rich in water and organic molecules, essential for life, and may have been a source for these molecules on Earth.
And while comet 67P has been visited before, that actually helps scientists, who will have a map of where to safely send their spacecraft, he pointed out.
The Titan spacecraft, Dragonfly, is a dual-quadcopter that would explore landing sites on Saturn's moon Titan, famous for its dark hydrocarbon lakes—long suggested as a potentially microbe-friendly world. The mission is led by Elizabeth Turtle from the Johns Hopkins University Applied Physics Laboratory.

Dragonfly would visit several locations tens and even hundreds of miles apart to study Titan's surface and atmosphere. It could explore in depth some of the places where satellites such as NASA's Cassini spacecraft (may it rest in peace) have gotten only a distant glimpse.
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Dragonfly is a dual-quadcopter lander that would take advantage of the environment on Titan to fly to multiple locations, some hundreds of miles apart, to sample materials and determine surface composition to investigate Titan's organic chemistry and habitability, monitor atmospheric and surface conditions, image landforms to investigate geological processes, and perform seismic studies. Credit: NASA
Like CAESAR, Dragonfly would be making a repeat visit: Cassini's Huygens probe landed on Titan in 2005 and studied the surface for less than a day. The robo-copter would take those studies much further, analyzing the moon's organic chemistry and habitability and the geological processes at play.
"In this way we can evaluate how far prebiotic chemistry has progressed in an environment that we know has the ingredients for life—for water-based life or potentially even hydrocarbon-based life," Turtle said.
These two missions have been selected for what's called a Phase A concept study, Green said. The mission teams' final proposals would be due in January 2019 and NASA would likely pick the winner that July. The winner would be slated for launch in the mid-2020s.
Whichever mission makes it to the launchpad will have big figurative shoes to fill. The last three New Frontiers missions were the New Horizons mission to Pluto, the Juno mission to Jupiter and the OSIRIS-REx mission now en route to the asteroid Bennu (and set to arrive in August 2018).
[Image: 1x1.gif] Explore further: APL proposes Dragonfly mission to explore potential habitable sites on Saturn's largest moon

67p ANU Mission to "bring back some quantum-quack"

The CAESAR (Comet Astrobiology Exploration SAmple Return) mission will acquire a sample from the nucleus of comet Churyumov-Gerasimenko, returning it safely to Earth.

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More Wine?

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NASA reveals finalists for next New Frontiers robotic mission: Saturn's moon Titan or Rosetta spacecraft's comet
December 21, 2017 by Amina Khan, Los Angeles Times
They have to go to Titan,
but they won't,
it's easier to make the comet mission happen.
We have seen a comet up close.
In our lifetimes we won't get another chance at Titan.
Not to mention Venus. 
Interesting pdf and excellent images in the pdf when you magnify to 400-500%

Tensile Strength of 67P/Churyumov-Gerasimenko Nucleus
Material from Overhangs


sample small image -- not the quality resolution seen in the pdf

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Comet Chury's late birth
March 6, 2018, University of Bern

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The final stage of a simulation, carried out by the authors, of a catastrophic collision between comets, showing one of the objects formed by re-accretion of debris from the collision, with a shape identical to that of Chury. Credit: ESA/Rosetta/Navcam - CC BY-SA IGO 3.0

Comets which consist of two parts, like Chury, can form after a catastrophic collision of larger bodies. Such collisions may have taken place in a later phase of our solar system, which suggests that Chury can be much younger than previously assumed. This is shown through computer simulations by an international research group with the participation of the University of Bern.

In the computer simulations, the research team investigated what happened after two large comet nuclei violently collided together. "The calculations showed that a large part of the material accumulates in many smaller bodies," explains Martin Jutzi of the Center for Space and Habitability (CSH) at the University of Bern and member of the National Centre of Competence in Research PlanetS. The newly created objects have different sizes and shapes, among them are many elongated bodies, some of which consist of two parts, just like the comet 67P/Churyumov-Gerasimenko, which the University of Bern studied in detail with the Bern mass spectrometer ROSINA on the Rosetta spacecraft.
"We were surprised that in such catastrophic collisions only a small part of the material is considerably compressed and heated," says Martin Jutzi. Moreover, this material is then ejected and hardly contributes to the formation of the smaller bodies that form a new generation of comet nuclei. On the side of the comet opposite the impact point, volatile substances can withstand even violent collisions. This is why the new generation of comets still has a low density and is rich in volatile substances—properties which have also been found on the comet Chury. Therefore, the duck-shaped comet may well have emerged after a violent, late collision and did not necessarily have to originate from the early formation phase of the solar system, as has been claimed repeatedly. Such collisions could have taken place relatively late in the life of the solar system. This finding has been reported in the journal Nature Astronomy by the research group led by Stephen Schwartz from the University of Côte d' Azur and the University of Arizona.

Simulations of comet collions. Credit: Université Côte d’Azur/University of Bern
Impact with a velocity of several kilometers per second
In previous studies, Martin Jutzi and Willy Benz, astrophysicist at CSH of the University of Bern and PlanetS director, had already come to the conclusion that Chury did not receive its two-component structure when our solar system was formed 4.5 billion years ago. The researchers showed that the weak point between the two parts of the comet could not have lasted for several billion years and that Chury may have been created by a comparatively gentle impact. "We have now investigated catastrophic collisions involving a lot more energy," explains Martin Jutzi. The new calculations confirm the previous results and extend the possible formation scenarios.

The research team investigated what happens when different sized bodies collide at different angles at speeds ranging from 20 to 3,000 meters per second. The simulations showed that small fragments merge into many transient aggregates in the hours and days after the collision (see video). The final shape is often the result of two or more large bodies that collide at very low speeds to form a two-component structure.
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Comet Chury taken by the Rosetta spacecraft. Credit: ESA/Rosetta/Navcam - CC BY-SA IGO 3.0

Possible explanation for "Chury's" mysterious structures
According to the simulations, during the days and weeks in which the comet received its shape, small aggregates in the vicinity continue to reaccumulate onto it. In reality, this material could be flattened when it hits the surface and thus lead to a layered structure. Moreover, if large blocks accumulate at this stage, cavities may be created which can develop into large pits. Such geological structures were discovered on Chury by the Rosetta mission – these observations were previously considered mysterious. "Our results not only confirm that the comet Chury may be much younger than previously assumed, but also provide a possible explanation for its striking structures," says Jutzi.

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 Explore further: Comet 67P/Churyumov-Gerasimenko is much younger than previously thought
More information: Stephen R. Schwartz et al. Catastrophic disruptions as the origin of bilobate comets, Nature Astronomy (2018). DOI: 10.1038/s41550-018-0395-2
Journal reference: Nature Astronomy
Provided by: University of Bern

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youareaduck Rabbitual.
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Research on optical illusion gives insight into how we perceive the world
When you look at the two images below, what do you see? Maybe you see two ducks, sitting side by side. Perhaps instead you see two rabbits. Maybe you see a duck and a rabbit.
[Image: 1x1.gif]1 hour ago in Psychology & Psychiatry 
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
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What'z inside 67p ?

Ugly ducklings: should rubber ducks be banned from the bath?
March 27, 2018

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Dark side of bath toys. Credit: Andri Bryner, Eawag

Scientific curiosity knows no bounds: a group of Swiss and US researchers have delved into "the dark side" of inviting rubber ducks and other flexible plastic toys into our tubs.

Any plastic materials dunked in bathwater provide ideal conditions for bacterial and fungal growth, according to the conclusions of the joint study, published Tuesday by the Swiss government.
"Dense growths of bacteria and fungi are found on the inner surface of these flexible toys, and a murky liquid will often be released when they are squeezed by a child," the Swiss government statement said.
The researchers from the Swiss Federal Institute of Aquatic Science and Technology EAWAG, the Swiss Federal Polytechnic School and the University of Illinois found that "diverse microbial growth is promoted not only by the plastic materials but by bath users themselves."
For their study, they carried out experiments with real bath toys and controls using new bath toys under conditions simulating household use.
Over a period of 11 weeks, they exposed some of the toys to clean and others to dirty bath water, containing things like soap and body fluids.
When they cut open the toys, "the findings sound unappetising: between five million and 75 million cells per square centimetre were observed on the inner surfaces," according to the summary of the report.
The researchers stressed though that there was a big difference between the plastic toys exposed to different types of water.
"Fungal species were detected in almost 60 percent of the real bath toys and in all the dirty-water control toys," the statement said.
"Potentially pathogenic bacteria were identified in 80 percent of all the toys studied, including Legionella and Pseudomonas aeruginosa," which is often the culprit in hospital-acquired infections, it added.
The main problem is that warm water gathers inside the toy, often made of low-quality polymers, which release organic carbon compounds that serve as nutrients to growing bacteria colonies.
"During bathing, other key nutrients such as nitrogen and phosphorus, as well as additional bacteria, are contributed by the human body (body fluids such as urine and sweat), external contaminants and personal care products," according to the study.
This allows bacteria and fungi to multiply inside of a toy children often enjoy using to squirt water into their faces.
"This could strengthen the immune system, which would be positive, but it can also result in eye, ear, or even gastrointestinal infections," microbiologist Frederik Hammes pointed out in Tuesday's statement.
So should we toss the ducks out with the bathwater? Or as some suggest on Internet comment forums, simply plug their holes to avoid the accumulation in their cavity?
Hammes suggests a more scientific approach: tighter regulations on the polymeric materials used to produce bath toys.
More information: Lisa Neu et al. Ugly ducklings—the dark side of plastic materials in contact with potable water, npj Biofilms and Microbiomes (2018). [url=]DOI: 10.1038/s41522-018-0050-9
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
I think that being exposed to bugs and microbes is a GOOD thing and does help with our own bio-dome inside our human bodies.

I always played in dirt, mud, grass, leaves, trees, tents and sand and water, snow etc.

It's likely what kept me alive through 7 OBE's from a bleed out requiring 36 scopes 18 in each direction to find a tiny leak in my internal intestines.

Not mentioning 4 open heart valve replacements.

As long as the toys aren't made from the stuff floating in the Pacific Ocean Naughty

Bob... Ninja Assimilated
"The Morning Light, No sensation to compare to this, suspended animation, state of bliss, I keep my eyes on the circling sky, tongue tied and twisted just and Earth Bound Martian I" Learning to Fly Pink Floyd [Video:]
Rosetta unravels formation of sunrise jets
May 23, 2018

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Left: Shortly after sunrise, impressive jets of gas and dust can be seen above the Hapi region on comet 67P/Churyumov-Gerasimenko. Right: Computer simulations reproduce these structures. Credit: © ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
The atmosphere of Rosetta's comet 67P/Churyumov-Gerasimenko is far from homogeneous. In addition to sudden outbursts of gas and dust, daily recurring phenomena at sunrise can be observed. In these, evaporating gas and entrained dust are concentrated to form jet-like structures. A new study, led by the Max Planck Institute for Solar System Research (MPS) in Germany and published in the journal Nature Astronomy, now identifies the rugged, duck-shaped structure of the comet as the main cause of these jets. Not only do concave regions collimate gas and dust emissions similar to an optical lens, the complex topography also provide some areas of the surface with more sunlight than others.

Far from the Sun, comets are lifeless, ice-cold bodies. When they progress into the inner solar system, they become active: frozen gases such as water evaporate and entrain dust particles from the surface. In this way the coma, a shroud of gas and dust, is formed. Already in images from earlier cometary missions such as Giotto, which flew by comet 1P/Halley in 1986, distinct jets of gas and dust were visible within the coma. They reach up to several kilometers into space. For scientists, these jets are the key to cometary activity. When and where do they occur? Which processes on the surface are involved? And what do they reveal about the nature and composition of the comet?

No mission has been able to pursue these questions in as great detail as ESA's Rosetta mission. From August 2014 to September 2016, the Rosetta spacecraft orbited comet 67P/Churyumov-Gerasimenko witnessing its transformation from an almost lifeless to a gas- and dust-spewing body from close-up. More than 70 000 images taken by the scientific camera system OSIRIS, which was developed and built under the leadership of MPS, document this process. They contain both eruptive, sudden outbursts of gas and dust, as well as jets that are stable for a longer time. In their most recent publication, researchers from the OSIRIS team have now investigated the activity that occurs regularly every morning.

"When the Sun rises over a part of the comet, the surface along the terminator almost instantaneously becomes active," first author Dr. Xian Shi from MPS describes. "The jets of gas and dust, which we then observe within the coma, are very reliable: they are found each morning in the same places and in a similar form," she adds. Responsible for this early morning activity is the frost, which forms at night on the cold comet surface. As soon as the Sun's rays touch it, it begins to evaporate.

"Outbursts can often be traced back to a small area on the surface where suddenly frozen water is exposed, for example due to a landslide," explains Dr. Holger Sierks from the MPS, OSIRIS Principal Investigator. "In the case of cometary activity at sunrise, this is different. The frost is distributed fairly evenly over the entire surface." But then why do the gas and dust emissions form jets? Why do they not create a completely homogeneous cloud?

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Along the vines of the Vineyard.
With a forked tongue the snake singsss...
Quote:The new analysis is consistent with team's original conclusion, that molecular oxygen is most likely primordial. Other theories have been proposed, and can't yet be ruled out, but the primordial theory currently fits the data best.

Molecular oxygen in comet's atmosphere not created on its surface
July 3, 2018 by Hayley Dunning, Imperial College London

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View of comet 67P taken by Rosetta. Credit: European Space Agency
Scientists have found that molecular oxygen around comet 67P is not produced on its surface, as some suggested, but may be from its body.

The European Space Agency's Rosetta spacecraft escorted comet 67P/Churyumov-Gerasimenko on its journey round the sun from August 2014—September 2016, dropping a probe and eventually crashing onto its surface.

When the comet is close enough to the sun the ice on its surface 'sublimes' - transforms from solid to gas—forming a gas atmosphere called a coma. Analysis of the coma by instruments on Rosetta revealed that it contained not only water, carbon monoxide and carbon dioxide, as anticipated, but also molecular oxygen.

Molecular oxygen is two oxygen atoms joined together, and on Earth it is essential for life, where it is produced by photosynthesis. It has been previously detected around some of the icy moons of Jupiter, but it was not expected to be found around a comet.

The Rosetta science team originally reported that the oxygen was most likely from the comet's main body, or nucleus. This meant it was 'primordial' - that it was already present when the comet itself formed at the beginning of the Solar System 4.6 billion years ago.

One group of outside researchers however suggested there might be a different source for molecular oxygen at comets. They had discovered a new way to produce molecular oxygen in space triggered by energetic ions—electrically charged molecules. They proposed that reactions with energetic ions on the surface of comet 67P could instead be the source of the detected molecular oxygen.

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Views of the comet form Rosetta. Credit: ESA
Now, members of the Rosetta team have analysed the data on 67P's oxygen in light of the new theory. In a paper published today in Nature Communications and led by Imperial College London physicists, they report that the proposed mechanism for producing oxygen on the surface of the comet is not sufficient to explain the observed levels in the coma.


Lead author Mr Kevin Heritier, from the Department of Physics at Imperial, said: "The first detection of molecular oxygen in 67P's coma was both very surprising and exciting".

"We tested the new theory of surface molecular oxygen production using observations of energetic ions, particles which trigger the surface processes which could lead to the production of molecular oxygen. We found that the amount of energetic ions present could not produce enough molecular oxygen to account for the amount of molecular oxygen observed in the coma."

Co-author Dr. Marina Galand, from the Department of Physics at Imperial and Science Co-Investigator of the Rosetta Plasma Consortium, added: "Surface generation of molecular oxygen may still happen on 67P, but the majority of the molecular oxygen in the coma is not produced through such a process."

The new analysis is consistent with team's original conclusion, that molecular oxygen is most likely primordial. Other theories have been proposed, and can't yet be ruled out, but the primordial theory currently fits the data best.

This is also supported by recent theories which revisited the formation of the molecular oxygen in dark clouds and the presence of molecular oxygen in the early Solar System. In this model, molecular oxygen created froze onto small dust grains. These grains collected more material, eventually building up the comet and locking the oxygen in the nucleus.

[Image: 1x1.gif] Explore further: Chemical engineers explain oxygen mystery on comets

More information: K. L. Heritier et al, On the origin of molecular oxygen in cometary comae, Nature Communications (2018). DOI: 10.1038/s41467-018-04972-5

Journal reference: Nature Communications [Image: img-dot.gif] [Image: img-dot.gif]
Provided by: Imperial College London

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Along the vines of the Vineyard.
With a forked tongue the snake singsss...
Rosetta witnesses birth of baby bow shock around comet
December 12, 2018, European Space Agency
You can see bow shocks also in front of a swimming duck
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Artist's impression of the infant bow shock detected by ESA's Rosetta spacecraft at Comet 67P/Churyumov-Gerasimenko. Credit: European Space Agency

Quote:[/url]What Is a Bow Shock? Voyager 1 Spacecraft is Arrived | HuffPost

Sep 12, 2013 - You can see bow shocks also in front of a swimming swan/duck, etc. Or just move your hand strongly through still water and get a shock wave ...[/size]

waves - Why is the angle of the wake of a duck constant? - Physics ...

4 answers
May 6, 2011 - The Kelvin wake does not describe the narrow turbulent band behind a ship, nor shock waves. The Kelvin wake consists of two types of waves: ...


A new study reveals that, contrary to first impressions, Rosetta did detect signs of an infant bow shock at the comet it explored for two years – the first ever seen forming anywhere in the solar system.

From 2014 to 2016, ESA's Rosetta spacecraft studied Comet 67P/Churyumov-Gerasimenko and its surroundings from near and far. It flew directly through the 'bow [url=]shock' several times both before and after the comet reached its closest point to the sun along its orbit, providing a unique opportunity to gather in situ measurements of this intriguing patch of space.

Comets offer scientists an extraordinary way to study the plasma in the solar system. Plasma is a hot, gaseous state of matter comprising charged particles, and is found in the solar system in the form of the solar wind: a constant stream of particles flooding out from our star into space.

As the supersonic solar wind flows past objects in its path, such as planets or smaller bodies, it first hits a boundary known as a bow shock. As the name suggests, this phenomenon is somewhat like the wave that forms around the bow of a ship as it cuts through choppy water. Bow shocks have been found around comets, too – Halley's comet being a good example. Plasma phenomena vary as the medium interacts with the surrounding environment, changing the size, shape, and nature of structures such as bow shocks over time.

Rosetta looked for signs of such a feature over its two-year mission, and ventured over 1500 km away from 67P's centre on the hunt for large-scale boundaries around the comet – but apparently found nothing.

Simulated view of Rosetta spying an infant bow shock at the comet. Click here for details and large versions of the video. Credit: ESA/Rosetta/RPC; H. Gunell et al (2018)"We looked for a classical bow shock in the kind of area we'd expect to find one, far away from the comet's nucleus, but didn't find any, so we originally reached the conclusion that Rosetta had failed to spot any kind of shock," says Herbert Gunell of the Royal Belgian Institute for Space Aeronomy, Belgium, and Umeå University, Sweden, one of the two scientists who led the study.

"However, it seems that the spacecraft actually did find a bow shock, but that it was in its infancy. In a new analysis of the data, we eventually spotted it around 50 times closer to the comet's nucleus than anticipated in the case of 67P. It also moved in ways we didn't expect, which is why we initially missed it."

On 7 March 2015, when the comet was over twice as far from the sun as the Earth and heading inwards towards our star, Rosetta data showed signs of a bow shock beginning to form. The same indicators were present on its way back out from the sun, on 24 February 2016. This boundary was observed to be asymmetric, and wider than the fully developed bow shocks observed at other comets.

"Such an early phase of the development of a bow shock around a comet had never been captured before Rosetta," says co-lead Charlotte Goetz of the Institute for Geophysics and Extraterrestrial Physics in Braunschweig, Germany.

"The infant shock we spotted in the 2015 data will have later evolved to become a fully developed bow shock as the comet approached the sun and became more active – we didn't see this in the Rosetta data, though, as the spacecraft was too close to 67P at that time to detect the 'adult' shock. When Rosetta spotted it again, in 2016, the comet was on its way back out from the sun, so the shock we saw was in the same state but 'unforming' rather than forming."

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Key moments in Rosetta's first year at comet 67P/Churyumov-Gerasimenko. Credit: European Space Agency
Herbert, Charlotte, and colleagues explored data from the Rosetta Plasma Consortium, a suite of instruments comprising five different sensors to study the plasma surrounding Comet 67P. They combined the data with a plasma model to simulate the comet's interactions with the solar wind and determine the properties of the bow shock.

The scientists found that, when the forming bow shock washed over Rosetta, the comet's magnetic field became stronger and more turbulent, with bursts of highly energetic charged particles being produced and heated in the region of the shock itself. Beforehand, particles had been slower-moving, and the solar wind had been generally weaker – indicating that Rosetta had been 'upstream' of a bow shock.

"These observations are the first of a bow shock before it fully forms, and are unique in being gathered on-location at the comet and shock itself," says Matt Taylor, ESA Rosetta Project Scientist.

"This finding also highlights the strength of combining multi-instrument measurements and simulations. It may not be possible to solve a puzzle using one dataset, but when you bring together multiple clues, as in this study, the picture can become clearer and offer real insight into the complex dynamics of our solar system – and the objects in it, like 67P."

[Image: 1x1.gif] Explore further: Image: Comet landscape

More information: Herbert Gunell et al. The infant bow shock: a new frontier at a weak activity comet, Astronomy & Astrophysics (2018). DOI: 10.1051/0004-6361/201834225 

Journal reference: Astronomy & Astrophysics [Image: img-dot.gif] [Image: img-dot.gif]
Provided by: European Space Agency
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
Rosetta's comet sculpted by stress

February 19, 2019, European Space Agency

[Image: rosettascome.jpg]
Single frame enhanced NavCam image taken on 27 March 2016, when Rosetta was 329 km from the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale is 28 m/pixel and the image measures 28.7 km across. Credit: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0

Feeling stressed? You're not alone. ESA's Rosetta mission has revealed that geological stress arising from the shape of Comet 67P/Churyumov–Gerasimenko has been a key process in sculpting the comet's surface and interior following its formation.

Small, icy comets with two distinct lobes seem to be commonplace in the solar system, with one possible mode of formation a slow collision of two primordial objects in the early stages of formation some 4.5 billion years ago. A new study using data collected by Rosetta during its two years at Comet 67P/C-G has illuminated the mechanisms that contributed to shaping the comet over the following billions of years.

The researchers used stress modelling and three-dimensional analyses of images taken by Rosetta's high resolution OSIRIS camera to probe the comet's surface and interior.

"We found networks of faults and fractures penetrating 500 metres underground, and stretching out for hundreds of metres," says lead author Christophe Matonti of Aix-Marseille University, France.

"These geological features were created by shear stress, a mechanical force often seen at play in earthquakes or glaciers on Earth and other terrestrial planets, when two bodies or blocks push and move along one another in different directions. This is hugely exciting: it reveals much about the comet's shape, internal structure, and how it has changed and evolved over time."

[Image: 1-rosettascome.jpg]
These images show how Rosetta’s dual-lobed comet, 67P/Churyumov-Gerasimenko, has been affected by a geological process known as mechanical shear stress. The comet’s shape is shown in the left two diagrams from top and side perspectives, …more
The model developed by the researchers found shear stress to peak at the centre of the comet's 'neck', the thinnest part of the comet connecting the two lobes.

"It's as if the material in each hemisphere is pulling and moving apart, contorting the middle part – the neck – and thinning it via the resulting mechanical erosion," explains co-author Olivier Groussin, also of Aix-Marseille University, France.

"We think this effect originally came about because of the comet's rotation combined with its initial asymmetric shape. A torque formed where the neck and 'head' meet as these protruding elements twist around the comet's centre of gravity."

The observations suggest that the shear stress acted globally over the comet and, crucially, around its neck. The fact that fractures could propagate so deeply into 67P/C-G also confirms that the material making up the interior of the comet is brittle, something that was previously unclear.

"None of our observations can be explained by thermal processes," adds co-author Nick Attree of the University of Stirling, UK. "They only make sense when we consider a shear stress acting over the entire comet and especially around its neck, deforming and damaging and fracturing it over billions of years."

[Image: 2-rosettascome.jpg]
This diagram illustrates the evolution of Rosetta’s dual-lobed comet, 67P/Churyumov-Gerasimenko, over the past 4.5 billion years. Credit: C. Matonti et al (2019)
Sublimation, the process of ices turning to vapour and resulting in comet dust being dragged out into space, is another well-known process that can influence a comet's appearance over time. In particular, when a comet passes closer to the Sun, it warms up and loses its ices more rapidly – perhaps best visualised in some of the dramatic outbursts captured by Rosetta during its time at Comet 67P/C–G.

The new results shed light on how dual-lobe comets have evolved over time.

Comets are thought to have formed in the earliest days of the solar system, and are stored in vast clouds at its outer edges before beginning their journey inwards. It would have been during this initial 'building' phase of the solar system that 67P/C-G got its initial shape.

The new study indicates that, even at large distances from the Sun, shear stress would then act over a timescale of billions of years following formation, while sublimation erosion takes over on shorter million-year timescales to continue shaping the comet's structure – especially in the neck region that was already weakened by shear stress.

Excitingly, NASA's New Horizons probe recently returned images from its flyby of Ultima Thule, a trans-Neptunian object located in the Kuiper belt, a reservoir of comets and other minor bodies at the outskirts of the solar system.

[Image: 3-rosettascome.jpg]
First impressions of the Kuiper Belt object Ultima Thule (left) revealed a surprisingly familiar appearance to the comet that ESA's Rosetta spacecraft explored for more than two years (right). Credit: Left: NASA/Johns Hopkins University …more
The data revealed that this object also has a dual-lobed shape, even though somewhat flattened with respect to Rosetta's comet.

"The similarities in shape are promising, but the same stress structures don't seem to be apparent in Ultima Thule," comments Christophe.
Ultima Thule  youareaduck  ??? 

As more detailed images are returned and analysed, time will tell if it has experienced a similar history to 67P/C-G or not.
"Comets are crucial tools for learning more about the formation and evolution of the solar system," says Matt Taylor, ESA's Rosetta Project Scientist.

"We've only explored a handful of comets with spacecraft, and 67P is by far the one we've seen in most detail. Rosetta is revealing so much about these mysterious icy visitors and with the latest result we can study the outer edges and earliest days of the solar system in a way we've never been able to do before."

[Image: 1x1.gif] Explore further: Image: Comet landscape

More information: C. Matonti et al. Bilobate comet morphology and internal structure controlled by shear deformation, Nature Geoscience (2019). DOI: 10.1038/s41561-019-0307-9 

Provided by: European Space Agency
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
All comets in the solar system might come from the same place
by Bryce Benda, Leiden University
[Image: allcometsint.jpg]This single frame Rosetta navigation camera image of Comet 67P/Churyumov-Gerasimenko was taken on 7 July 2015 from a distance of 154 km from the comet centre. Credit: ESA/Rosetta/NAVCAM
All comets might share their place of birth, new research says. For the first time ever, astronomer Christian Eistrup applied chemical models to fourteen well-known comets, surprisingly finding a clear pattern. His publication has been accepted in the journal Astronomy & Astrophysics.

[b]Comets: balls of ice or more?[/b]
Comets travel through our solar system and are composed of ice, dust, and small rock-like particles. Their nuclei can be as large as tens of kilometers across. "Comets are everywhere, and sometimes with very funky orbits around the Sun. In the past, comets even have hit the Earth," Christian Eistrup says. "We know what comets consist of and which molecules are present in them. They vary in composition, but are normally seen as just one group of icy balls. Therefore, I wanted to know whether comets are indeed one group, or whether different subsets can be made."
[b]A new take on comets[/b]
"What if I apply our existing chemical models to comets?", Eistrup thought during his Ph.D. at Leiden University. In the research team at Leiden Observatory, which included Kavli Prize winner Ewine van Dishoeck, he developed models to predict the chemical composition of protoplanetary discs—flat discs of gas and dust encompassing young stars. Understanding these discs can give insight into how stars and planets form. Conveniently, these Leiden models turned out to be of help in learning about comets and their origins.
"I thought it would be interesting to compare our chemical models with published data on comets," says the astronomer. "Luckily, I had the help of Ewine. We did some statistics to pin down if there was a special time or place in our young solar system, where our chemical models meet the data on comets." This happened to be the case, and to a surprising extent. Where the researchers hoped for a number of comets sharing similarities, it turned out that all fourteen comets showed the same trend. "There was a single model that fitted each comet best, thereby indicating that they share their origin."

Credit: Leiden University
And that origin is somewhere close to our young Sun, when it was still encircled by a protoplanetary disc and our planets were still forming. The model suggests a zone around the Sun, inside the range where carbon monoxide becomes ice—relatively far away from the nucleus of the young Sun. "At these locations, the temperature varies from 21 to 28 Kelvin, which is around minus 250 degrees Celsius. That's very cold, so cold that almost all the molecules we know are ice.

"From our models, we know that there are some reactions taking place in the ice phase—although very slowly, in a time-frame of 100,000 to 1 million years. But that could explain why there are different comets with different compositions."
But if comets come from the same place, how do they end up in different places and orbits in our solar system? "Although we now think they formed in similar locations around the young Sun, the orbits of some of these comets could be disturbed—for instance by Jupiter—which explains the different orbits."
[b]Comet data hunter[/b]
As befits a scientist, Eistrup places some side-notes to his publication. "With only fourteen comets, the sample is quite small. That's why I'm currently hunting for data on many more comets, to run them through our models and further test our hypothesis." Eistrup also hopes that astronomers that study the origin of our solar system and its evolution can use his results. "Our research suggests that comets have formed during the period they're studying, so this new information might give them new insights."
He is also keen to get in touch with other comet researchers. "Because we show a new trend, I would like to discuss what other astronomers think of our research."
[b]The seeds of life[/b]
Comets and life on Earth, they go hand in hand. "We still don't know how life on Earth began. But the chemistry on comets could lead to the production of organic molecules, including some building blocks for life. And if the right comet hits the right planet, with the right environment, life could start growing," Eistrup concludes. So, interestingly, understanding the birth of comets potentially could help us understand the birth of life on Earth.

Explore further
Image: ESA, NASA's SOHO sees bright sungrazer comet

[b]More information:[/b] Cometary compositions compared with protoplanetary disk midplane chemical evolution. An emerging chemical evolution taxonomy for comets. arXiv:1907.11255 [astro-ph.EP]
[b]Journal information:[/b] Astronomy & Astrophysics [/url]

Provided by [url=]Leiden University
Along the vines of the Vineyard.
With a forked tongue the snake singsss...

Posted by EA - Tuesday, September 10th, 2019, 05:14 pm

All comets in the solar system might come from the same place
by Bryce Benda, Leiden University

more Arrow

SEPTEMBER 20, 2019
Comet gateway discovered to inner solar system, may alter fundamental understanding of comet evolution
by Zenaida Gonzalez Kotala, University of Central Florida
[Image: cometgateway.jpg]An artist rendered image of what Centaur SW1 would look like as an inner solar system Jupiter-Family comet at a distance of 0.2 AU (30 million km, 19 million miles) from Earth. The Moon is in the upper right part of the frame for scale. Credit: University of Arizona/Heather Roper
A new study led by a University of Central Florida researcher may fundamentally alter our understanding of how comets arrive from the outskirts of the solar system and are funneled to the inner solar system coming closer to Earth.

In a study to be published in the Astrophysical Journal Letters this week, scientist Gal Sarid and co-authors describe the discovery of an orbital "gateway" through which many comets pass before they approach our sun. The gateway was uncovered as part of a simulation of centaurs, small icy bodies traveling on chaotic orbits between Jupiter and Neptune. The study team modeled the evolution of bodies from beyond Neptune's orbit, through the giant planet's region, and inside Jupiter's orbit. These icy bodies are considered nearly pristine remnants of material from the birth of our solar system.
For a long time, the pathway of comets from their original formation location inward toward the sun has been debated.
"How do new comets, controlled by Jupiter's influence, replace those that are lost? Where is the transition between residing in the outer solar system, as small dormant bodies, and becoming active inner solar system bodies, exhibiting a widespread gas and dust coma and tail?" asks Sarid, the lead scientist for the study. These questions remained a mystery until now. "What we discovered, the gateway model as a 'cradle of comets,' will change the way we think about the history of icy bodies," he says.
Centaurs are thought to originate in the Kuiper Belt region beyond Neptune and are considered as the source of Jupiter Family Comets, which occupy the inner solar system. The chaotic nature of centaur orbits obscures their exact pathways making it difficult to predict their future as comets. When icy bodies such as centaurs or comets approach the sun, they begin to release gas and dust to produce the fuzzy appearance of the coma and extended tails that we refer to as comets. This display is among the most impressive phenomena observable in the night sky, but it is also a fleeting flicker of beauty that is rapidly followed by either the destruction of the comet or its evolution to a dormant state, Sarid says.
The original goal of the investigation was to explore the history of a peculiar centaur– 29P/Schwassmann-Wachmann 1 (SW1), a mid-sized centaur in a nearly circular orbit just beyond Jupiter. SW1 has long puzzled astronomers with its high activity and frequent explosive outbursts that occur at a distance from the sun where ice should not effectively vaporize. Both its orbit and activity put SW1 in an evolutionary middle ground between the other centaurs and the Jupiter Family Comets. The research team wanted to explore whether SW1's circumstances were consistent with the orbital progression of the other centaurs, Sarid says.

"More than one in five centaurs that we tracked were found to enter an orbit similar to that of SW1 at some point in their lifetime," said Maria Womack, a Florida Space Institute scientist and co-author of the study. "Rather than being a peculiar outlier, SW1 is a centaur caught in the act of dynamically evolving into a JFC." In addition to the commonplace nature of SW1's orbit, the simulations lead to an even more surprising discovery, Womack says.
"Centaurs passing through this region are the source of more than two thirds of all JFCs, making this the primary gateway through which these comets are produced," says Womack. The Gateway region does not hold resident objects for long, with most centaurs becoming JFCs within a few thousand years. This is a short portion of any solar system object's lifetime, which can span millions and sometimes billions of years.
The presence of the gateway provides a long sought-after means of identifying the centaurs on an imminent trajectory toward the inner solar system. SW1 is currently the largest and most active of the handful of objects discovered in this gateway region, which makes it a "prime candidate to advance our knowledge of the orbital and physical transitions that shape the comet population we see today," Sarid says.
Our understanding of comets is intimately linked to knowing our solar system's early composition and the evolution of conditions for atmospheres and life to arise, the researchers said.

Explore further
NASA's Wise finds mysterious centaurs may be comets

[b]More information:[/b] Gal Sarid, et al. 29P/Schwassmann-Wachmann 1, A Centaur in the Gateway to the Jupiter-Family Comets. arXiv:1908.04185v2 [astro-ph.EP]:
[b]Journal information:[/b] Astrophysical Journal Letters [/url]

Provided by [url=]University of Central Florida

SEPTEMBER 18, 2019
Comet's collapsing cliffs and bouncing boulders
[Image: cometscollap.jpg]An example of a boulder having moved across the surface of Comet 67P/Churyumov-Gerasimenko’s surface, captured in Rosetta’s OSIRIS imagery. The image was taken with the narrow-angle camera and shows the boulder in the lower third of the image. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA (CC BY-SA 4.0);
Scientists analyzing the treasure trove of images taken by ESA's Rosetta mission have turned up more evidence for curious bouncing boulders and dramatic cliff collapses.

Rosetta operated at Comet 67P/Churyumov-Gerasimenko between August 2014 and September 2016, collecting data on the comet's dust, gas and plasma environment, its surface characteristics and its interior structure.
As part of the analysis of some 76 000 high-resolution images captured with its OSIRIS camera, scientists have been looking for surface changes. In particular, they are interested in comparing the period of the comet's closest approach to the Sun—known as perihelion—with that after this most active phase, to better understand the processes that drive surface evolution.
Loose debris is seen all over the comet, but sometimes boulders have been caught in the act of being ejected into space, or rolling across the surface. A new example of a bouncing boulder was recently identified in the smooth neck region that connects the comet's two lobes, an area that underwent a lot of noticeable large-scale surface changes over the course of the mission. There, a boulder about 10 m-wide has apparently fallen from the nearby cliff, and bounced several times across the surface without breaking, leaving "footprints" in the loosely consolidated surface material.

[Image: 2-cometscollap.jpg]
An example of a boulder having moved across the surface of Comet 67P/Churyumov-Gerasimenko’s surface, captured in Rosetta’s OSIRIS imagery. The first image (left) provides a reference view of the comet, along with a close-up of the region under study. The smaller insets on the right show before and after images of the region containing the bouncing boulder, captured on 17 March 2015 and 19 June 2016, respectively. Impressions of the boulder have been left in the soft regolith covering the comet’s surface as it bounced to a halt. It is thought to have fallen from the nearby cliff, which is about 50 m high. The graphic at the bottom illustrates the path of the boulder as it bounced across the surface, with preliminary measurements of the ‘craters’ calculated. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA (CC BY-SA 4.0); Analysis: J-B. Vincent et al (2019)
"We think it fell from the nearby 50 m-high cliff, and is the largest fragment in this landslide, with a mass of about 230 tonnes," said Jean-Baptiste Vincent of the DLR Institute for Planetary Research, who presented the results at the EPSC-DPS conference in Geneva today.
"So much happened on this comet between May and December 2015 when it was most active, but unfortunately because of this activity we had to keep Rosetta at a safe distance. As such we don't have a close enough view to see illuminated surfaces with enough resolution to exactly pinpoint the 'before' location of the boulder."
Studying boulder movements like these in different parts of the comet helps determine the mechanical properties of both the falling material, and the surface terrain on which it lands. The comet's material is in general very weak compared with the ice and rocks we are familiar with on Earth: boulders on Comet 67P/C-G are around one hundred times weaker than freshly packed snow.

Another type of change has also been witnessed in several locations around the comet: the collapse of cliff faces along lines of weakness, such as the dramatic capture of the fall of a 70 m-wide segment of the Aswan cliff observed in July 2015. But Ramy El-Maarry and Graham Driver of Birkbeck, University of London, may have found an even larger collapse event, linked to a bright outburst seen on 12 September 2015 along the northern-southern hemisphere divide.

[Image: 3-cometscollap.jpg]
Before and after a cliff collapse on Comet 67P/Churyumov-Gerasimenko. In the upper panels the yellow arrows show the location of a scarp at the boundary between the illuminated northern hemisphere and the dark southern hemisphere of the small lobe at times before and after the outburst event (September 2014 and June 2016, respectively). The lower panels show close-ups of the upper panels; the blue arrow points to the scarp that appears to have collapsed in the image after the outburst. Two boulders (1and 2) are marked for orientation. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA (CC BY-SA 4.0)
"This seems to be one of the largest cliff collapses we've seen on the comet during Rosetta's lifetime, with an area of about 2000 square meters collapsing," said Ramy, also speaking at EPSC-DPS today.
During perihelion passage, the southern hemisphere of the comet was subjected to high solar input, resulting in increased levels of activity and more intensive erosion than elsewhere on the comet.
"Inspection of before and after images allow us to ascertain that the scarp was intact up until at least May 2015, for when we still have high enough resolution images in that region to see it," says Graham, an undergraduate student working with Ramy to investigate Rosetta's vast image archive.
"The location in this particularly active region increases the likelihood that the collapsing event is linked to the outburst that occurred in September 2015."

[Image: cometscollap.gif]
Comet outburst 12 September 2015. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA (CC BY-SA 4.0)
Looking in detail at the debris around the collapsed region suggests that other large erosion events have happened here in the past. Ramy and Graham found that the debris includes blocks of variable size ranging up to tens of meters, substantially larger than the boulder population following the Aswan cliff collapse, which is mainly comprised of boulders a few meters diameter.
"This variability in the size distribution of the fallen debris suggests either differences in the strength of the comet's layered materials, and/or varying mechanisms of cliff collapse," adds Ramy.
Studying comet changes like these not only gives insight into the dynamic nature of these small bodies on short timescales, but the larger scale cliff collapses provide unique views into the internal structure of the comet, helping to piece together the comet's evolution over longer timescales.
"Rosetta's datasets continue to surprise us, and it's wonderful the next generation of students are already making exciting discoveries," adds Matt Taylor, ESA's Rosetta project scientist.

Explore further
Image: Comet landscape

[b]More information:[/b] Cliff Collapses on Comet 67P/Churyumov-Gerasimenko Following Outbursts as Observed by the Rosetta Mission: meetingorganizer.copernicus.or … C-DPS2019-1727-1.pdf
Provided by European Space Agency

Along the vines of the Vineyard.
With a forked tongue the snake singsss...

I think this is not very well thought out. ... and that is being polite.

I underlined two quick vague and contradictory statements.

Quote:All comets in the solar system might come from the same place

... somewhere close to our young Sun, 
when it was still encircled by a protoplanetary disc, 
and our planets were still forming. 
The model suggests a zone around the Sun, 
inside the range where carbon monoxide becomes ice—
relatively far away from the nucleus of the young Sun.


The computer models are somewhere between lame to feeble,
due to lack of sampling data.  Naughty

In x ray diffraction of minerals, as I did ... looking at a specific type of mineral for instance,
you can test 20 samples,
and draw a few quick consistent conclusions, 
and pretend you well on your way to being an expert.
But after you have tested 2000 samples,
all of a sudden you have a far bigger map of interconnected data, 
and suddenly,
the first quick consistent conclusions have a new spectrum of unpredictable or flexible possibilities, 
to outright errors in the initial analysis.
New factors appear,
with volumes of sample data accumulated. 

Quote:As befits a scientist, 
Eistrup places some side-notes to his publication Whip

"With only fourteen comets, 
the sample is quite small.  Doh

That's why I'm currently hunting for data on many more comets, 
to run them through our models  Tp
and further test Wall our hypothesis."

14 comets, 12 monkeys, 5 funky chickens, and a Partridge in a pear tree ...
is not,
enough sample data.

DECEMBER 3, 2019
NASA's exoplanet-hunting mission catches a natural comet outburst in unprecedented detail
[Image: nasasexoplan.gif]This animation shows an explosive outburst of dust, ice and gases from comet 46P/Wirtanen that occurred on September 26, 2018 and dissipated over the next 20 days. The images, from NASA's TESS spacecraft, were taken every three hours during the first three days of the outburst. Credit: Farnham et al./NASA
Using data from NASA's Transiting Exoplanet Survey Satellite (TESS), astronomers at the University of Maryland (UMD), in College Park, Maryland, have captured a clear start-to-finish image sequence of an explosive emission of dust, ice and gases during the close approach of comet 46P/Wirtanen in late 2018. This is the most complete and detailed observation to date of the formation and dissipation of a naturally-occurring comet outburst. The team members reported their results in the November 22 issue of The Astrophysical Journal Letters.

"TESS spends nearly a month at a time imaging one portion of the sky. With no day or night breaks and no atmospheric interference, we have a very uniform, long-duration set of observations," said Tony Farnham, a research scientist in the UMD Department of Astronomy and the lead author of the research paper. "As comets orbit the Sun, they can pass through TESS' field of view. Wirtanen was a high priority for us because of its close approach in late 2018, so we decided to use its appearance in the TESS images as a test case to see what we could get out of it. We did so and were very surprised!"
"While TESS is a powerhouse for discovering planets orbiting nearby, bright stars, its observing strategy enables so much exciting additional science," said TESS project scientist Padi Boyd of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Since the TESS data are rapidly made public through NASA's Mikulski Archive for Space Telescopes (MAST), it's exciting to see scientists identifying which data are of interest to them, and then doing all kinds of additional serendipitous science beyond exoplanets."
Normal comet activity is driven by sunlight vaporizing the ices near the surface of the nucleus, and the outflowing gases drag dust off the nucleus to form the coma. However, many comets are known to experience occasional spontaneous outbursts that can significantly, but temporarily increase the comet's activity. It is not currently known what causes outbursts, but they are related to the conditions on the comet's surface. A number of potential trigger mechanisms have been proposed, including a thermal event, in which a heat wave penetrates into a pocket of highly volatile ices, causing the ice to rapidly vaporize and produce an explosion of activity, and a mechanical event, where a cliff collapses, exposing fresh ice to direct sunlight. Thus, studies of the outburst behavior, especially in the early brightening stages that are difficult to capture, can help us understand the physical and thermal properties of the comet.
Although Wirtanen came closest to Earth on December 16, 2018, the outburst occurred earlier in its approach, beginning on September 26, 2018. The initial brightening of the outburst occurred in two distinct phases, with an hour-long flash followed by a more gradual second stage that continued to grow brighter for another 8 hours. This second stage was likely caused by the gradual spreading of comet dust from the outburst, which causes the dust cloud to reflect more sunlight overall. After reaching peak brightness, the comet faded gradually over a period of more than two weeks. Because TESS takes detailed, composite images every 30 minutes, the team was able to view each phase in exquisite detail.

"With 20 days' worth of very frequent images, we were able to assess changes in brightness very easily. That's what TESS was designed for, to perform its primary job as an exoplanet surveyor," Farnham said. "We can't predict when comet outbursts will happen. But even if we somehow had the opportunity to schedule these observations, we couldn't have done any better in terms of timing. The outburst happened mere days after the observations started."
The team has generated a rough estimate of how much material may have been ejected in the outburst, about one million kilograms (2.2 million pounds), which could have left a crater on the comet of around 20 meters (about 65 feet) across. Further analysis of the estimated particle sizes in the dust tail may help improve this estimate. Observing more comets will also help to determine whether multi-stage brightening is rare or commonplace in comet outbursts.
TESS has also detected for the first time Wirtanen's dust trail. Unlike a comet's tail—the spray of gas and fine dust that follows behind a comet, growing as it approaches the sun—a comet's trail is a field of larger debris that traces the comet's orbital path as it travels around the sun. Unlike a tail, which changes direction as it is blown by the solar wind, the orientation of the trail stays more or less constant over time.
"The trail more closely follows the orbit of the comet, while the tail is offset from it, as it gets pushed around by the sun's radiation pressure. What's significant about the trail is that it contains the largest material," said Michael Kelley, an associate research scientist in the UMD Department of Astronomy and a co-author of the research paper. "Tail dust is very fine, a lot like smoke. But trail dust is much larger—more like sand and pebbles. We think comets lose most of their mass through their dust trails. When the Earth runs into a comet's dust trail, we get meteor showers."
While the current study describes initial results, Farnham, Kelley and their colleagues look forward to further analyses of Wirtanen, as well as other comets in TESS' field of view. "We also don't know what causes natural outbursts and that's ultimately what we want to find," Farnham said. "There are at least four other comets in the same area of the sky where TESS made these observations, with a total of about 50 comets expected in the first two years' worth of TESS data. There's a lot that can come of these data."

Explore further
See a passing comet this Sunday

[b]More information:[/b] Tony L. Farnham et al, First Results from TESS Observations of Comet 46P/Wirtanen, The Astrophysical Journal (2019). DOI: 10.3847/2041-8213/ab564d
[b]Journal information:[/b] Astrophysical Journal Letters  Astrophysical Journal [/url]

Provided by [url=]NASA's Goddard Space Flight Center
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
JANUARY 21, 2020
Flight through the comet Chury's dust cloud resolves chemical mystery
[Image: flightthroug.jpg]A plume of dust from Comet 67P/Churyumov–Gerasimenko, seen by the OSIRIS Wide Angle Camera on ESA's Rosetta spacecraft on 3 July 2016. The shadow of the plume is cast across the basin, which is in the Imhotep region. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Under the leadership of astrophysicist Kathrin Altwegg, Bernese researchers have found an explanation for why very little nitrogen could previously be accounted for in the nebulous covering of comets: the building block for life predominantly occurs in the form of ammonium salts, the occurrence of which could not previously be measured. The salts may be a further indication that comet impacts may have made life on Earth possible in the first place.

More than 30 years ago, the European comet mission Giotto flew past Halley's comet. The Bernese ion mass spectrometer IMS, led by Prof. em. Hans Balsiger, was on board. A key finding from the measurements taken by this instrument was that there appeared to be a lack of nitrogen in Halley's coma—the nebulous covering of comets which forms when a comet passes close to the sun. Although nitrogen (N) was discovered in the form of ammonia (NH3) and hydrocyanic acid (HCN), the incidence was far removed from the expected cosmic incidence. More than 30 years later, researchers have solved this mystery thanks to a happy accident. This is a result of the analysis of data from the Bernese mass spectrometer ROSINA, which collected data on the comet 67P/Churyumov-Gerasimenko, called Chury for short, on board the ESA space probe Rosetta (see info box below).
[b]Risky flight through the comet Chury's dust cloud[/b]
Less than a month before the end of the Rosetta mission, the space probe was just 1.9 km above the surface of Chury as it flew through a dust cloud from the comet. This resulted in a direct impact of dust in the ion source of the mass spectrometer ROSINA-DFMS (Rosetta Orbiter Sensor for Ion and Neutral Analysis-Double Focusing Mass Spectrometer), led by the University of Bern. Kathrin Altwegg, lead researcher on ROSINA and co-author of the new study published today in the prestigious journal Nature Astronomy, says: "This dust almost destroyed our instrument and confused Rosetta's position control."
Thanks to the flight through the dust cloud, it was possible to detect substances which normally remain in the cold environment of the comet on the dust particles and therefore cannot be measured. The amount of particles, some of which had never before been measured on a comet, was astonishing. In particular, the incidence of ammonia, the chemical compound of nitrogen and hydrogen with the formula NH3, was suddenly many times greater. "We came up with the idea that the incidence of ammonia in the ROSINA data could potentially be traced back to the occurrence of ammonium salts," explains Altwegg. "As a salt, ammonia has a much higher evaporation temperature than ice and is therefore mostly present in the form of a solid in the cold environment of a comet. It has not been possible to measure these solids either through remote sensing with telescopes or on the spot until now."
[b]Ammonium salt and its role in the emergence of life[/b]
Extensive laboratory work was needed in order to prove the presence of these salts in cometary ice. "The ROSINA team has found traces of five different ammonium salts: ammonium chloride, ammonium cyanide, ammonium cyanate, ammonium formate and ammonium acetate," says the chemist on the ROSINA team and co-author of the current study, Dr. Nora Hänni. "Until now, the apparent absence of nitrogen on comets was a mystery. Our study now shows that it is very probable that nitrogen is present on comets, namely in the form of ammonium salts," Hänni continues.
The ammonium salts discovered include several astrobiologically relevant molecules which may result in the development of urea, amino acids, adenine and nucleotides. Kathrin Altwegg says: "This is definitely a further indication that comet impacts may be linked with the emergence of life on Earth."

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Astronomers reveal interstellar thread of one of life's building blocks

[b]More information:[/b] Kathrin Altwegg et al. Evidence of ammonium salts in comet 67P as explanation for the nitrogen depletion in cometary comae, Nature Astronomy (2020). DOI: 10.1038/s41550-019-0991-9
[b]Journal information:[/b] Nature Astronomy [/url]

Provided by 
University of Bern

JANUARY 15, 2020
Astronomers reveal interstellar thread of one of life's building blocks
by ESO
[Image: astronomersr.jpg]This infographic shows the key results from a study that has revealed the interstellar thread of phosphorus, one of life's building blocks. Thanks to ALMA, astronomers could pinpoint where phosphorus-bearing molecules form in star-forming regions like AFGL 5142. The background of this infographic shows a part of the night sky in the constellation of Auriga, where the star-forming region AFGL 5142 is located. The ALMA image of this object is on the top left of the infographic, and one of the locations where the team found phosphorus-bearing molecules is indicated by a circle. The most common phosphorus-bearing molecule in AFGL 5142 is phosphorus monoxide, represented in orange and red in the diagram on the bottom left. Another molecule found was phosphorus nitride, represented in orange and blue. Using data from the ROSINA instrument onboard ESA's Rosetta, astronomers also found phosphorus monoxide on comet 67P/Churyumov-Gerasimenko, shown on the bottom right. This first sighting of phosphorus monoxide on a comet helps astronomers draw a connection between star-forming regions, where the molecule is created, all the way to Earth, where it played a crucial role in starting life. Credit: ALMA (ESO/NAOJ/NRAO), Rivilla et al.; ESO/L. Calçada; ESA/Rosetta/NAVCAM; Mario Weigand,
Phosphorus, present in our DNA and cell membranes, is an essential element for life as we know it. But how it arrived on the early Earth is something of a mystery. Astronomers have now traced the journey of phosphorus from star-forming regions to comets using the combined powers of ALMA and the European Space Agency's probe Rosetta. Their research shows, for the first time, where molecules containing phosphorus form, how this element is carried in comets, and how a particular molecule may have played a crucial role in starting life on our planet.

"Life appeared on Earth about 4 billion years ago, but we still do not know the processes that made it possible," says Víctor Rivilla, the lead author of a new study published today in the journal Monthly Notices of the Royal Astronomical Society. The new results from the Atacama Large Millimeter/Submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner, and from the ROSINA instrument on board Rosetta, show that phosphorus monoxide is a key piece in the origin-of-life puzzle.
With the power of ALMA, which allowed a detailed look into the star-forming region AFGL 5142, astronomers could pinpoint where phosphorus-bearing molecules, like phosphorus monoxide, form. New stars and planetary systems arise in cloud-like regions of gas and dust in between stars, making these interstellar clouds the ideal places to start the search for life's building blocks.
The ALMA observations showed that phosphorus-bearing molecules are created as massive stars are formed. Flows of gas from young massive stars open up cavities in interstellar clouds. Molecules containing phosphorus form on the cavity walls, through the combined action of shocks and radiation from the infant star. The astronomers have also shown that phosphorus monoxide is the most abundant phosphorus-bearing molecule in the cavity walls.
After searching for this molecule in star-forming regions with ALMA, the European team moved on to a Solar System object: the now-famous comet 67P/Churyumov-Gerasimenko. The idea was to follow the trail of these phosphorus-bearing compounds. If the cavity walls collapse to form a star, particularly a less-massive one like the Sun, phosphorus monoxide can freeze out and get trapped in the icy dust grains that remain around the new star. Even before the star is fully formed, those dust grains come together to form pebbles, rocks and ultimately comets, which become transporters of phosphorus monoxide.

ROSINA, which stands for Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, collected data from 67P for two years as Rosetta orbited the comet. Astronomers had found hints of phosphorus in the ROSINA data before, but they did not know what molecule had carried it there. Kathrin Altwegg, the Principal Investigator for Rosina and an author in the new study, got a clue about what this molecule could be after being approached at a conference by an astronomer studying star-forming regions with ALMA: "She said that phosphorus monoxide would be a very likely candidate, so I went back to our data and there it was!"
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Credit: ESO
This first sighting of phosphorus monoxide on a comet helps astronomers draw a connection between star-forming regions, where the molecule is created, all the way to Earth.
"The combination of the ALMA and ROSINA data has revealed a sort of chemical thread during the whole process of star formation, in which phosphorus monoxide plays the dominant role," says Rivilla, who is a researcher at the Arcetri Astrophysical Observatory of INAF, Italy's National Institute for Astrophysics.
"Phosphorus is essential for life as we know it," adds Altwegg. "As comets most probably delivered large amounts of organic compounds to the Earth, the phosphorus monoxide found in comet 67P may strengthen the link between comets and life on Earth."
This intriguing journey could be documented because of the collaborative efforts between astronomers. "The detection of phosphorus monoxide was clearly thanks to an interdisciplinary exchange between telescopes on Earth and instruments in space," says Altwegg.
Leonardo Testi, ESO astronomer and ALMA European Operations Manager, concludes: "Understanding our cosmic origins, including how common the chemical conditions favourable for the emergence of life are, is a major topic of modern astrophysics. While ESO and ALMA focus on the observations of molecules in distant young planetary systems, the direct exploration of the chemical inventory within our Solar System is made possible by ESA missions, like Rosetta. The synergy between world leading ground-based and space facilities, through the collaboration between ESO and ESA, is a powerful asset for European researchers and enables transformational discoveries like the one reported in this paper."
This research was presented in a paper to appear in Monthly Notices of the Royal Astronomical Society.

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Comet contains glycine, key part of recipe for life

[b]More information:[/b] ALMA and ROSINA detections of phosphorus-bearing molecules: the interstellar thread between star-forming regions and comets, Monthly Notices of the Royal Astronomical Society (2020).
[b]Journal information:[/b] Monthly Notices of the Royal Astronomical Society 

Provided by [url=]ESO
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
Friday, November 14th, 2014, 11:50 pm

"Silicon dioxides would release oxygen and that would combine with the hydrogen in the solar wind.  Now you have your water.  The soft landing was into dust created by this activity.  Occam's razor."

Arnik. Although the Albedo of 67P/C-G is blacker than coal Could this concievably make the coma at any point even briefly in time to appear RED?from either a space imager or from earth based observations. [Image: dunno.gif]

[Image: 350px-Red_comet_by_dhadkan.jpg]

holy quackin'  chameleon  youareaduck  camel lions!

I finally get an answer! ~5.5 years later... #19 LilD

Friday, November 14th, 2014, 11:50 pm  Arrow
FEBRUARY 6, 2020

Rosetta data reveals process behind color-changing chameleon comet
[Image: rosettaandth.jpg]Two years of data from Rosetta's VIRTIS instrument has shown that comet 67P/Churyumov-Gerasimenko subtly changed colour as it drew close to the Sun and moved away from it again. When far from the Sun the nucleus of the comet was redder than the surrounding particles in the coma, which were dominated by water ice grains measuring about 100 micrometres across. Howev-er, as the comet drew close to the Sun, the nucleus became bluer because fresh ice was revealed. In contrast, the coma became redder as sub-micrometre dust grains made of organic matter and carbon were thrown off the comet. When the comet moved away from the Sun, the activity on the comet decreased and the colours returned to the nucleus being redder than the coma. Credit: European Space Agency
A grand synthesis of Rosetta data has shown how its target comet repeatedly changed color during the two years it was watched by the spacecraft. The chameleon comet's nucleus became progressively less red as it made its close pass around the sun, and then red again as it returned to deep space.

Just like a chameleon changes its color depending on its environment, so too did comet 67P/Churyumov-Gerasimenko. Unlike a chameleon, the color changes on 67P/C-G reflect the amount of water ice that is exposed on the surface and in the surroundings of the comet.
At the beginning of Rosetta's mission, the spacecraft rendezvoused with the comet while it was still a long way from the sun. At such distances, the surface was covered in layers of dust and little ice was visible. This meant the surface appeared red when analyzed with the VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) instrument.
As the comet drew closer it crossed an important boundary, known as the frost line. Occurring at a distance around three times further from the sun than the Earth, anything within the frostline will be heated sufficiently by the sun that the ice will turn into a gas, a process called sublimation.
As Rosetta followed 67P/C-G across the frostline, VIRTIS began to notice the color of the comet change. As the comet approached the sun, the heating increased and the hidden water ice began to sublime pushing away the dust grains too. This revealed layers of pristine ice, which made the nucleus turn bluer in color as seen by VIRTIS.
Around the comet's nucleus, the situation was reversed. When the comet was far from the sun, there was little dust surrounding the comet, but what there was contained water ice and so appeared bluer. This surrounding dust cloud is called the coma.
As the comet crossed the frostline, the ice in the dust grains surrounding the nucleus sublimed quickly, leaving just the dehydrated dust grains. And so the coma turned redder as it approached perihelion, its closest approach to the sun.
Once the comet was heading back into the outer solar system, VIRTIS showed the color situation reverse again, so the nucleus became redder and the coma bluer.

[Image: 1-rosettaandth.jpg]
Rosetta navigation camera (NavCam) image taken on 7 July 2015 at 154 km from the centre of comet 67P/Churyumov-Gerasimenko. The image measures 13.4 km across and has a scale of about 13.1 m/pixel. The image has been cleaned to remove the more obvious bad pixels and cosmic ray artefacts, and intensities have been scaled. Credit: ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0
To track the way the comet evolved, the VIRTIS team had to analyze more than 4000 separate observations spanning across two years of the Rosetta mission.

"To answer the big question of how does a comet work it is very important to have a long time series such as this," says Gianrico Filacchione from Italy's INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, who led the study.
The reason is that comets are extremely dynamic environments. Jets tend to swiftly appear on their surfaces and then decrease just as suddenly. Therefore, comparing occasional snap shots risks our understanding of the comet's long-term evolution being biased by the transient changes. Having such a large quantity of measurements, however, means that even short timescale changes can be tracked.
"The correlation of what is happening on the nucleus is something completely new that cannot be done from Earth," says Gianrico.
This is because ground observations cannot resolve a comet's nucleus, which in the case of 67P/CG is only about 3 km in size. Now that the team can describe and understand both the long-term evolution of the comet, and the steps it took along the way, it means that the readings from the other instruments onboard Rosetta can be placed into context.
But that does not mean we know everything about comets. Spectral analysis shows that the red color of the dust is created by so-called organic molecules. These are molecules made of carbon, and there is a rich variety of them on the comet. Scientists believe that they are important for understanding how life formed on Earth.
In order to study them up close and identify these molecules, however, would require a sample of the comet's surface to be returned to Earth. "Bringing back to Earth a piece of the comet is really the Holy Grail for a cometary mission," says Gianrico.
Until that is possible, however, he will continue to use the VIRTIS data to investigate 67P/C-G's organics.
"There are definitely more exciting results to come," says Matt Taylor, ESA Project Scientist for Rosetta, "The data collection may be over, but the analysis and the results will continue for years yet, adding to the rich legacy of cometary knowledge provided by Rosetta."

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Video: Rosetta's ongoing science

[b]More information:[/b] Gianrico Filacchione et al. An orbital water-ice cycle on comet 67P from colour changes, Nature (2020). DOI: 10.1038/s41586-020-1960-2
[b]Journal information:[/b] Nature
Along the vines of the Vineyard.
With a forked tongue the snake singsss...
MARCH 13, 2020
Puzzle about nitrogen solved thanks to cometary analogs
[Image: puzzleaboutn.jpg]Gas and dust rise from “Chury’s” surface as the comet approaches the point of its orbit closest to the sun. Credit: ESA/Rosetta/NAVCAM
One of the basic building blocks of life is nitrogen. An international consortium was able to detect ammonium salt containing nitrogen on the cometary surface of Chury thanks to a method using analogs for comet material. The method on which the study on the detection of ammonium salt is based was developed at the University of Bern.

Comets and asteroids are objects in our solar system that have not developed much since the planets were formed. As a result, they are in a sense the archives of the solar system, and determining their composition could also contribute to a better understanding of the formation of the planets.
One way to determine the composition of asteroids and comets is to study the sunlight reflected by them, since the materials on their surface absorb sunlight at certain wavelengths. We talk about a comet's spectrum, which has certain absorption features. VIRTIS (Visible, InfraRed and Thermal Imaging Spectrometer) on board the European Space Agency's (ESA) Rosetta space probe mapped the surface of comet 67P/Churyumov-Gerasimenko, known as Chury for short, from August 2014 to May 2015. The data gathered by VIRTIS showed that the cometary surface is uniform almost everywhere in terms of composition: The surface is very dark and slightly red in color, because of a mixture of complex, carbonaceous compounds and opaque minerals. However, the exact nature of the compounds responsible for the measured absorption features on Chury has been difficult to establish until now.

[Image: 1-1-puzzleaboutn.jpg]
Comparison of the spectrum of the artificial comet containing ammonium salt (in red) with the spectrum of the surface of the comet "Chury" (in black). The core of the comet is about 4 km long. Credit: (top left image) ESA/Rosetta/NAVCAM - CC BY-SA IGO 3.0 The artificial comet is produced in the laboratory in a 5 cm diameter container (bottom left image) Poch et al., 2020).
[b]Cometary analogue provided the solution to the puzzle[/b]
To identify which compounds are responsible for the absorption features, researchers led by Olivier Poch from the Institute of Planetology and Astrophysics at the Université de Grenoble Alpes carried out laboratory experiments in which they created cometary analogues and simulated conditions similar to those in space. Poch had developed the method together with researchers from Bern when he was still working at the University of Bern Physics Institute. The researchers tested various potential compounds on the cometary analogues and measured their spectra, just as the VIRTIS instrument on board Rosetta had done with Chury's surface. The experiments showed that ammonium salts explain specific features in the spectrum of Chury.
Antoine Pommerol from the University of Bern Physics Institute is one of the co-authors of the study, which is now published in Science. He explains: "While Olivier Poch was working at the University of Bern, we jointly developed methods and procedures to create replicas of the surfaces of cometary nuclei." The surfaces were altered by sublimating the ice on them under simulated space conditions. "These realistic laboratory simulations allow us to compare laboratory results and data recorded by the instruments on Rosetta or other comet missions. The new study builds on these methods to explain the strongest spectral feature observed by the VIRTIS spectrometer with Chury," Pommerol continues. Nicolas Thomas, Director of the University of Bern Physics Institute and also co-author of the study, says: "Our laboratory in Bern offers the ideal opportunities to test ideas and theories with experiments that have been formulated on the basis of data gathered by instruments on space missions. This ensures that the interpretations of the data are really plausible."

[Image: 5e6b723f3c8c7.jpg]
Recipe to produce an artificial cometary surface in the laboratory. Ice-dust particles are put under vacuum and low temperature. Ice sublimates, leaving a porous dust layer on the surface. Credit: Poch et al. Science (2020)
[b]Vital building block "hides" in ammonium salts[/b]

The results are identical to those from the Bern mass spectrometer ROSINA, which had also gathered data on Chury on board Rosetta. A study published in Nature Astronomy in February under the leadership of astrophysicist Kathrin Altwegg was the first to detect nitrogen, one of the basic building blocks of life, in the nebulous covering of comets. It had "hidden" itself in the nebulous covering of Chury in the form of ammonium salts, the occurrence of which could not be measured until now.
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Artificial cometary surface (5-cm in diameter) made of opaque minerals and ammonium salts. Particles move in the gas flow produced by the sublimation of water ice located underneath. Credit: Olivier Poch, UGA, CNES, CNRS
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Artificial cometary surface (5-cm in diameter) produced at IPAG laboratory, after sublimation of fine particles of water ice mixed with opaque minerals in a simulation chamber. Credit: Olivier Poch, UGA, CNES, CNRS
Although the exact amount of salt is still difficult to estimate from the available data, it is likely that these ammonium salts contain most of the nitrogen present in the Chury comet. According to the researchers, the results also contribute to a better understanding of the evolution of nitrogen in interstellar space and its role in prebiotic chemistry.

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Flight through the comet Chury's dust cloud resolves chemical mystery

[b]More information:[/b] Olivier Poch et al. Ammonium salts are a reservoir of nitrogen on a cometary nucleus and possibly on some asteroids, Science (2020). DOI: 10.1126/science.aaw7462
[b]Journal information:[/b] Science  Nature Astronomy [/url]

Provided by [url=]University of Bern
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