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First Light: Hayabusa 2 @ Ryugu.
3 / 3 / 2018.  This mission deserves a standalone thread.

Eyes on Target: Japan’s Hayabusa 2 Takes First Images of Asteroid Ryugu
March 2, 2018  
[Image: 67ab02d97d6b158f66eaece2589afeb6-512x362.jpg]Artist’s Impression of Hayabusa 2 Approaching Ryugu – Image: Akihiro Ikeshita
Japan’s Hayabusa 2 spacecraft – on a quest to touch an asteroid – has set its sight on its destination in late February via the first detection of asteroid Ryugu by the craft’s Telescopic Optical Navigation Camera that will be used to guide it into close proximity to the distant world later this year.
The probe still has over a million Kilometers to cover in order to reach its target in June for a one-and-a-half-year exploration mission that will see the spacecraft dispatch a series of landers and an impactor while also making contact with Ryugu itself to scoop up sample material to be returned to Earth in December 2020.
The first optical images of Ryugu, only appearing as a speck of light, were taken by the faraway spacecraft on February 26, Day 1,181 of the Hayabusa 2 mission that started back on December 3, 2014 with a successful launch atop an H-IIA rocket that sent the 590-Kilogram craft on a three-and-a-half-year journey to Ryugu – a 920-meter C-type primitive body that is hoped to hold a treasure trove of scientific information in the form of a preserved record of the early days of the solar system.

[Image: Ryugu_firstlight_20180228_NN_shift_CR2-1-512x355.jpg]Credit: JAXA, Hayabusa Consortium
Sent off at a top speed of 11.8 Kilometers per second (relative to Earth), Hayabusa 2 entered a heliocentric orbit and completed 547 hours of ion engine firings between March and September 2015 to adjust course for an Earth flyby on December 3rd that saw the spacecraft zip past the planet at an altitude of around 3,090 Kilometers and borrow some of Earth’s angular momentum to speed up in its orbit around the sun to reach asteroid Ryugu. The speedy flyby provided a welcome opportunity for exercising the craft’s instrument suite and collecting calibration data of a very well-known target.
Heading back out, Hayabusa 2 was set for two major orbit-adjustment campaigns using its ion engines to slowly catch up with Ryugu that orbits the sun at 0.96 by 1.42 astronomical units. Some testing of the craft’s critical systems including the long-distance Ka-Band communications link were carried out along the way and the ion engines were operated for 794 hours between March and May 2016 to adjust the craft’s solar orbit by changing its speed by 127 m/s and adding a brief fine-tuning maneuver of 40 cm/s. The second orbit-adjustment campaign between November 2016 and May 2017 operated three of the four engines for 2,558 hours to change the craft’s speed by 435 m/s.

[Image: renzoku2-512x320.jpg]Earth Flyby Montage – Image: JAXA
[Image: hayabusa2orbits-512x279.jpg]Hayabusa Orbit Evolution – Image: JAXA
Hayabusa began firing three of its four ion engines again on January 10, 2018 marking the initiation of the far-field approach phase to take the spacecraft toward its destination with ion engine operation planned to last until early June when the final approach phase will be initiated from a distance of 2,500 Kilometers. Until June, the ion engines are expected to operate for 2,700 hours for a total delta-v of around 400 meters per second.
On February 26, Hayabusa pointed its Telescopic Optical Navigation Camera ONC-T toward Ryugu’s location and snapped approximately 300 images, a subset of which were transmitted on the 27th and indeed show the asteroid at an optical magnitude of 9. At the time the images were taken, the spacecraft was still 1.3 million Kilometers from its destination.
The ONC-T images provided independent confirmation that Hayabusa 2 is on the correct approach course toward Ryugu in addition to constant radio tracking of the spacecraft’s trajectory. According to Project Management, the spacecraft remains in excellent health and the current ion propulsion phase will proceed with maximum thrust.
Reaching the approach point in early June, Hayabusa 2 will rely on its three Optical Navigation Cameras to provide relative navigation data used by mission teams on Earth to plan the spacecraft’s final approach, first into a 20-Kilometer surveying orbit where the spacecraft is expected to arrive by July 5th. It will then be set for a step-wise descent first to five and then to one Kilometer from Ryugu’s surface to collect detailed remote-sensing data of the asteroid using a pair of infrared spectrometers tasked with studying the energy balance of the asteroid as well as its chemical composition.

[Image: 2311622_orig-512x349.jpg]Photo: JAXA
The primary payload of Hayabusa 2 is a sample collection system that will acquire small amounts of surface samples during as many as three brief touchdowns of the main spacecraft on the asteroid’s surface using a high-fidelity navigation system that allows the spacecraft to make contact with the surface just long enough to shoot down a projectile and scoop up lifted dust through a sampling horn.
Furthermore, the spacecraft will dispatch four landers – the 10-Kilogram MASCOT lander built in Europe for an in-situ study of surface composition and properties, and three MINERVA landers to deliver imagery and temperature measurements. All landers will make several hops across the asteroid’s surface to take measurements at different locations.
>>Detailed Spacecraft, Instrument, Lander & Science Overview

[url=][Image: 5482225_orig-512x362.jpg]Image: Akihiro Ikeshita
Another payload of the mission is an impactor device that will be deployed towards the asteroid and use high-explosives to generate a high-speed impact that is hoped to expose material from under the asteroid’s surface for later collection by Hayabusa 2. A deployable camera will be used to document the impact of the penetrator.
The number of touch-and-go attempts and landers to be dispatched not only makes Hayabusa 2 one of the most complex missions currently in operation but also creates a packed schedule for the 18 months it plans to spend in proximity to the asteroid. Per current planning schedules, the initial touchdown and lander deployment is planned for September/October followed by a brief intermission ahead of touchdown #2 in February 2019, the release of the impactor in March/April and the third touchdown one month later. Departure of Ryugu is expected in December 2019 for a one-year return journey expected to culminate with the high-speed re-entry and landing of the hermetically sealed Sample Return Capsule in Australia.

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

Yes it does deserve its own thread.

Bob... Ninja Assimilated
"The Light" - Jefferson Starship-Windows of Heaven Album
I'm an Earthling with a Martian Soul wanting to go Home.   
You have to turn your own lightbulb on. ©stevo25 & rhw007
pyrene to graphene + 'magic angle' = @ Ryugu. ?

Quote: Wrote:"Starting off from simple gases, you can generate one-dimensional and two-dimensional structures, and pyrene could lead you to 2-D graphene," Ahmed said. "From there you can get to graphite, and the evolution of more complex chemistry begins."

Chemical sleuthing unravels possible path to forming life's building blocks in space
March 5, 2018, Lawrence Berkeley National Laboratory

[Image: chemicalsleu.jpg]
An asteroid belt orbits a star in this artist's rendering. In a new study, experiments at Berkeley Lab explored possible chemical pathways that could form complex hydrocarbons -- like those found in some meteorite samples -- in space. Credit: NASA/JPL-Caltech

Scientists have used lab experiments to retrace the chemical steps leading to the creation of complex hydrocarbons in space, showing pathways to forming 2-D carbon-based nanostructures in a mix of heated gases.

The latest study, which featured experiments at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), could help explain the presence of pyrene, which is a chemical compound known as a polycyclic aromatic hydrocarbon, and similar compounds in some meteorites.
A team of scientists, including researchers from Berkeley Lab and UC Berkeley, participated in the study, published March 5 in the Nature Astronomy journal. The study was led by scientists at the University of Hawaii at Manoa and also involved theoretical chemists at Florida International University.
"This is how we believe some of the first carbon-based structures evolved in the universe," said Musahid Ahmed, a scientist in Berkeley Lab's Chemical Sciences Division who joined other team members to perform experiments at Berkeley Lab's Advanced Light Source (ALS).

"Starting off from simple gases, you can generate one-dimensional and two-dimensional structures, and pyrene could lead you to 2-D graphene," Ahmed said. "From there you can get to graphite, and the evolution of more complex chemistry begins."

Pyrene has a molecular structure composed of 16 carbon atoms and 10 hydrogen atoms. Researchers found that the same heated chemical processes that give rise to the formation of pyrene are also relevant to combustion processes in vehicle engines, for example, and the formation of soot particles.
The latest study builds on earlier work that analyzed hydrocarbons with smaller molecular rings that have also been observed in space, including in Saturn's moon Titan - namely benzene and naphthalene.
Ralf I. Kaiser, one of the study's lead authors and a chemistry professor at the University of Hawaii at Manoa, said, "When these hydrocarbons were first seen in space, people got very excited. There was the question of how they formed." Were they purely formed through reactions in a mix of gases, or did they form on a watery surface, for example?
Ahmed said there is an interplay between astronomers and chemists in this detective work that seeks to retell the story of how life's chemical precursors formed in the universe.

"We talk to astronomers a lot because we want their help in figuring out what's out there," Ahmed said, "and it informs us to think about how it got there."
Kaiser noted that physical chemists, on the other hand, can help shine a light on reaction mechanisms that can lead to the synthesis of specific molecules in space.
[Image: 1-chemicalsleu.jpg]
Reaction pathways that can form a hydrocarbon called pyrene through a chemical method known as hydrogen-abstraction/acetylene-addition, or HACA, is shown at the top. At bottom, some possible steps by which pyrene can form more complex hydrocarbons via HACA (red) or another mechanism (blue) called hydrogen abstraction -- vinylacetylene addition (HAVA). Credit: Long Zhao, Ralf I. Kaiser, et al./Nature Astronomy, DOI: 10.1038/s41550-018-0399-y

Pyrene belongs to a family known as polycyclic aromatic hydrocarbons, or PAHs, that are estimated to account for about 20 percent of all carbon in our galaxy. PAHs are organic molecules that are composed of a sequence of fused molecular rings. To explore how these rings develop in space, scientists work to synthesize these molecules and other surrounding molecules known to exist in space.
Alexander M. Mebel, a chemistry professor at Florida International University who participated in the study, said, "You build them up one ring at a time, and we've been making these rings bigger and bigger. This is a very reductionist way of looking at the origins of life: one building block at a time."
For this study, researchers explored the chemical reactions stemming from a combination of a complex hydrocarbon known as the 4-phenanthrenyl radical, which has a molecular structure that includes a sequence of three rings and contains a total of 14 carbon atoms and nine hydrogen atoms, with acetylene (two carbon atoms and two hydrogen atoms).
Chemical compounds needed for the study were not commercially available, said Felix Fischer, an assistant professor of chemistry at UC Berkeley who also contributed to the study, so his lab prepared the samples. "These chemicals are very tedious to synthesize in the laboratory," he said.
At the ALS, researchers injected the gas mixture into a microreactor that heated the sample to a high temperature to simulate the proximity of a star. The ALS generates beams of light, from infrared to X-ray wavelengths, to support a range of science experiments by visiting and in-house researchers.
The mixture of gases was jetted out of the microreactor through a tiny nozzle at supersonic speeds, arresting the active chemistry within the heated cell. The research team then focused a beam of vacuum ultraviolet light from the synchrotron on the heated gas mixture that knocked away electrons (an effect known as ionization).
They then analyzed the chemistry taking place using a charged-particle detector that measured the varied arrival times of particles that formed after ionization. These arrival times carried the telltale signatures of the parent molecules. These experimental measurements, coupled with Mebel's theoretical calculations, helped researchers to see the intermediate steps of the chemistry at play and to confirm the production of pyrene in the reactions.
Mebel's work showed how pyrene (a four-ringed molecular structure) could develop from a compound known as phenanthrene (a three-ringed structure). These theoretical calculations can be useful for studying a variety of phenomena, "from combustion flames on Earth to outflows of carbon stars and the interstellar medium," Mebel said.
Kaiser added, "Future studies could study how to create even larger chains of ringed molecules using the same technique, and to explore how to form graphene from pyrene chemistry."
Other experiments conducted by team members at the University of Hawaii will explore what happens when researchers mix hydrocarbon gases in icy conditions and simulate cosmic radiation to see whether that may spark the creation of life-bearing molecules.
"Is this enough of a trigger?" Ahmed said. "There has to be some self-organization and self-assembly involved" to create life forms. "The big question is whether this is something that, inherently, the laws of physics do allow."
 Explore further: A hot start to the origin of life? Researchers map the first chemical bonds that eventually give rise to DNA
More information: Long Zhao et al, Pyrene synthesis in circumstellar envelopes and its role in the formation of 2D nanostructures, Nature Astronomy (2018). DOI: 10.1038/s41550-018-0399-y

Journal reference: Nature Astronomy [/url]
Provided by:
Lawrence Berkeley National Laboratory

Quote: Wrote:"Starting off from simple gases, you can generate one-dimensional and two-dimensional structures, and pyrene could lead you to 2-D graphene," Ahmed said.
"From there you can get to graphite, and the evolution of more complex chemistry begins."

When rotated at a 'magic angle,' graphene sheets can form an insulator or a superconductor
March 5, 2018 by Jennifer Chu, Massachusetts Institute of Technology

[Image: whenrotateda.jpg]
Physicists at MIT and Harvard University have found that graphene, a lacy, honeycomb-like sheet of carbon atoms, can behave at two electrical extremes: as an insulator, in which electrons are completely blocked from flowing; and as a superconductor, in which electrical current can stream through without resistance. Credit: MIT

It's hard to believe that a single material can be described by as many superlatives as graphene can. Since its discovery in 2004, scientists have found that the lacy, honeycomb-like sheet of carbon atoms - essentially the most microscopic shaving of pencil lead you can imagine - is not just the thinnest material known in the world, but also incredibly light and flexible, hundreds of times stronger than steel, and more electrically conductive than copper.

Now physicists at MIT and Harvard University have found the wonder material can exhibit even more curious electronic properties. In two papers published today in Nature, the team reports it can tune graphene to behave at two electrical extremes: as an insulator, in which electrons are completely blocked from flowing; and as a superconductor, in which electrical current can stream through without resistance.

Researchers in the past, including this team, have been able to synthesize graphene superconductors by placing the material in contact with other superconducting metals - an arrangement that allows graphene to inherit some superconducting behaviors. This time around, the team found a way to make graphene superconduct on its own, demonstrating that superconductivity can be an intrinsic quality in the purely carbon-based material.

The physicists accomplished this by creating a "superlattice" of two graphene sheets stacked together - not precisely on top of each other, but rotated ever so slightly, at a "magic angle" of 1.1 degrees.

As a result, the overlaying, hexagonal honeycomb pattern is offset slightly, creating a precise moiré configuration that is predicted to induce strange, "strongly correlated interactions" between the electrons in the graphene sheets. In any other stacked configuration, graphene prefers to remain distinct, interacting very little, electronically or otherwise, with its neighboring layers.

The team, led by Pablo Jarillo-Herrero, an associate professor of physics at MIT, found that when rotated at the magic angle, the two sheets of graphene exhibit nonconducting behavior, similar to an exotic class of materials known as Mott insulators. When the researchers then applied voltage, adding small amounts of electrons to the graphene superlattice, they found that, at a certain level, the electrons broke out of the initial insulating state and flowed without resistance, as if through a superconductor.

"We can now use graphene as a new platform for investigating unconventional superconductivity," Jarillo-Herrero says. "One can also imagine making a superconducting transistor out of graphene, which you can switch on and off, from superconducting to insulating. That opens many possibilities for quantum devices."


A 30-year gap

A material's ability to conduct electricity is normally represented in terms of energy bands. A single band represents a range of energies that a material's electrons can have. There is an energy gap between bands, and when one band is filled, an electron must embody extra energy to overcome this gap, in order to occupy the next empty band.

A material is considered an insulator if the last occupied energy band is completely filled with electrons. Electrical conductors such as metals, on the other hand, exhibit partially filled energy bands, with empty energy states which the electrons can fill to freely move.

Mott insulators, however, are a class of materials that appear from their band structure to conduct electricity, but when measured, they behave as insulators. Specifically, their energy bands are half-filled, but because of strong electrostatic interactions between electrons (such as charges of equal sign repelling each other), the material does not conduct electricity. The half-filled band essentially splits into two miniature, almost-flat bands, with electrons completely occupying one band and leaving the other empty, and hence behaving as an insulator.

"This means all the electrons are blocked, so it's an insulator because of this strong repulsion between the electrons, so nothing can flow," Jarillo-Herrero explains. "Why are Mott insulators important? It turns out the parent compound of most high-temperature superconductors is a Mott insulator."

In other words, scientists have found ways to manipulate the electronic properties of Mott insulators to turn them into superconductors, at relatively high temperatures of about 100 Kelvin. To do this, they chemically "dope" the material with oxygen, the atoms of which attract electrons out of the Mott insulator, leaving more room for remaining electrons to flow. When enough oxygen is added, the insulator morphs into a superconductor. How exactly this transition occurs, Jarillo-Herrero says, has been a 30-year mystery.

"This is a problem that is 30 years and counting, unsolved," Jarillo-Herrero says. "These high-temperature superconductors have been studied to death, and they have many interesting behaviors. But we don't know how to explain them."

A precise rotation

Jarillo-Herrero and his colleagues looked for a simpler platform to study such unconventional physics. In studying the electronic properties in graphene, the team began to play around with simple stacks of graphene sheets. The researchers created two-sheet superlattices by first exfoliating a single flake of graphene from graphite, then carefully picking up half the flake with a glass slide coated with a sticky polymer and an insulating material of boron nitride.

They then rotated the glass slide very slightly and picked up the second half of the graphene flake, adhering it to the first half. In this way, they created a superlattice with an offset pattern that is distinct from graphene's original honeycomb lattice.

The team repeated this experiment, creating several "devices," or graphene superlattices, with various angles of rotation, between 0 and 3 degrees. They attached electrodes to each device and measured an electrical current passing through, then plotted the device's resistance, given the amount of the original current that passed through.

"If you are off in your rotation angle by 0.2 degrees, all the physics is gone," Jarillo-Herrero says. "No superconductivity or Mott insulator appears. So you have to be very precise with the alignment angle."

At 1.1 degrees - a rotation that has been predicted to be a "magic angle" - the researchers found the graphene superlattice electronically resembled a flat band structure, similar to a Mott insulator, in which all electrons carry the same energy regardless of their momentum.

"Imagine the momentum for a car is mass times velocity," Jarillo-Herrero says. "If you're driving at 30 miles per hour, you have a certain amount of kinetic energy. If you drive at 60 miles per hour, you have much higher energy, and if you crash, you could deform a much bigger object. This thing is saying, no matter if you go 30 or 60 or 100 miles per hour, they would all have the same energy."

"Current for free"

For electrons, this means that, even if they are occupying a half-filled energy band, one electron does not have any more energy than any other electron, to enable it to move around in that band. Therefore, even though such a half-filled band structure should act like a conductor, it instead behaves as an insulator - and more precisely, a Mott insulator.

This gave the team an idea: What if they could add electrons to these Mott-like superlattices, similar to how scientists doped Mott insulators with oxygen to turn them into superconductors? Would graphene assume superconducting qualities in turn?

To find out, they applied a small gate voltage to the "magic-angle graphene superlattice," adding small amounts of electrons to the structure. As a result, individual electrons bound together with other electrons in graphene, allowing them to flow where before they could not. Throughout, the researchers continued to measure the electrical resistance of the material, and found that when they added a certain, small amount of electrons, the electrical current flowed without dissipating energy - just like a superconductor.

"You can flow current for free, no energy wasted, and this is showing graphene can be a superconductor," Jarillo-Herrero says.

Perhaps more importantly, he says the researchers are able to tune graphene to behave as an insulator or a superconductor, and any phase in between, exhibiting all these diverse properties in one single device. This is in contrast to other methods, in which scientists have had to grow and manipulate hundreds of individual crystals, each of which can be made to behave in just one electronic phase.

"Usually, you have to grow different classes of materials to explore each phase," Jarillo-Herrero says. "We're doing this in-situ, in one shot, in a purely carbon device. We can explore all those physics in one device electrically, rather than having to make hundreds of devices. It couldn't get any simpler."

  Explore further: Atomically thin building blocks could make optoelectrical devices more efficient

More information: Correlated Insulator Behaviour at Half-Filling in Magic Angle Graphene Superlattices, Nature (2018).

Journal reference: Nature
Provided by: Massachusetts Institute of Technology

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

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