Tag: Ryugu

Scientists detect the five chemicals that make up DNA/RNA inside Ryugu samples

11:05 am

Ryugu's northern hemisphere
Ryugu as seen by Hayabusa-2 shortly before it grabbed
samples from the surface. Arrow indicates planned touchdown
site.

Scientists studying the samples brought back from the asteroid Ryugu by Japan’s probe Hayabusa-2 have found therein a full set of the five fundamental chemicals that make up either DNA or RNA: adenine, guanine, cytosine, thymine and uracil. From the paper’s [pdf] abstract:

Organic molecules delivered from extraterrestrial materials may have played a key role in supplying building blocks for life on Earth. Here we report all five canonical nucleobases—purines (adenine and guanine) and pyrimidines (cytosine, thymine and uracil)—in samples returned from the C-type asteroid (162173) Ryugu by JAXA’s Hayabusa2 mission and compare the results with data from similar extraterrestrial material.

Ryugu samples contain nearly equal amounts of purines and pyrimidines, whereas Murchison is enriched in purines and Bennu and Orgueil in pyrimidines. Samples from Ryugu, Bennu and Orgueil, which have a similar mineralogy and elemental composition, show purine-to-pyrimidine ratios negatively correlating with ammonia.

These observations indicate that the nucleobases in these samples may have formed via a shared pathway depending on the physicochemical environment of the respective parent bodies. The detection of diverse nucleobases in asteroid and meteorite materials demonstrates their widespread presence throughout the Solar System and reinforces the hypothesis that carbonaceous asteroids contributed to the prebiotic chemical inventory of early Earth.

In other words, the data from these samples suggests that the formation of life on Earth was greatly aided by the deposition of these carbon molecules from asteroids onto the Earth.

At the same time, some caution must be exercised. At present we only have samples from three asteroids, one of which (Orgueil) was obtained shortly after it crashed on Earth. It will take a much larger census of many in-space asteroids to confirm this hypothesis.

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Scientists link near Earth asteroids Bennu and Ryugu to much larger main belt asteroid

9:29 am

Ryugu and Bennu

Scientists comparing the spectroscopy of samples returned from the near Earth asteroids Bennu and Ryugu have found they closely resemble the much larger main belt asteroid Polana, suggesting all three formed at the same time and place.

You can read the paper here [pdf] From the press release:

The study compared spectroscopy data from Polana with spacecraft and laboratory data from Bennu and Ryugu samples, discovering similarities in their near-infrared spectrum sufficient to support the theory that they originate from the same parent asteroid. “Very early in the formation of the solar system, we believe large asteroids collided and broke into pieces to form an ‘asteroid family’ with Polana as the largest remaining body,” said SwRI’s Dr. Anicia Arredondo, lead author of the study. “Theories suggest that remnants of that collision not only created Polana, but also Bennu and Ryugu as well.”

While the similarities are great, the paper notes there are differences, possibly from “space weathering, particle size, surface texture, or different compositions.” The scientists believe the differences were caused by the asteroids’ different environments, with the 33-mile-wide and much older Polana in the asteroid belt beyond Mars, and Ryugu and Bennu, both less than a mile wide, orbiting the Sun inside Mars.

It is also possible the asteroids have little to do with each other, and the similar spectroscopy only informs us of some of the more common components of the early solar system.

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Scientists discover unexpected mineral in Ryugu asteroid sample

1:21 pm

Scientists analyzing the samples brought back from the rubble pile asteroid Ryugu by Japan’s Hayabusa-2 spacecraft have now discovered an unexpected mineral, dubbed djerfisherite, that the formation theories of the asteroid say should not be there.

“Djerfisherite is a mineral that typically forms in very reduced environments, like those found in enstatite chondrites, and has never been reported in CI chondrites or other Ryugu grains,” says first and corresponding author Masaaki Miyahara, associate professor at the Graduate School of Advanced Science and Engineering, Hiroshima University. “Its occurrence is like finding a tropical seed in Arctic ice—indicating either an unexpected local environment or long-distance transport in the early solar system.”

At present the scientists propose two hypotheses for explaining the mineral. Either it came from another asteroid as Ryugu was congealing, or it formed in Ryugu when conditions raised its temperature above 350 degrees Celsius. The researchers now favor the latter theory, even though the generally accepted histories of Ryugu’s formation never included such conditions.

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Japan’s Hayabusa-2 asteroid probe in safe mode

9:29 am

Japan’s Hayabusa-2 asteroid probe, which had successfully dropped off samples from the rubble-pile asteroid Ryugu in 2020 and then was sent on a long journey to visit two more asteroids, has suffered an unknown anomaly and shifted into safe mode to protect its instruments.

Communications between Earth and the spacecraft were stable, however, and teams were investigating the situation and its impact on the extended mission, a machine translation of the post read. JAXA has yet to provide a new update since posting about the anomaly.

If engineers can identify the problem and bring the spacecraft back into full operations, the hope is that it will fly past another asteroid in 2026 on its way to a third in 2031, where it will remain for a period of time doing more detailed observations.

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Samples from the asteroid Bennu reshape entirely our understanding of the solar system’s early make-up

11:11 am

Nightingale landing site on Bennu
The sample site on Bennu, with OSIRIS-REx
superimposed for scale. Click for full image.

First, I hope my readers will notice that — unlike NASA and the entire press — I make no mention in my headline above of the discovery of a “mix of life’s ingredients” or “the key building blocks of life” from the samples brought back by the probe OSIRIS-REx from the asteroid Bennu.

This is the game NASA does all the time, to hint at the discovery of life when this is not the real discovery. NASA does it because it knows that if you hint at such a discovery, the press will go crazy and give you lots of press.

The real news from the two papers published this week, available here and here, however, is more fundamental. Before the samples from Bennu and Ryugu (brought back by the Japanese probe Hayabusa-2) had arrived, our understanding of the make-up and chemistry of the early solar system was very incomplete and badly biased. The only asteroid samples we had of carbonaceous chondrite asteroids, the most primitive and fragile carbon-rich asteroids in the solar system, had came from meteorites that had survived the journey through the Earth’s atmosphere. Thus, the only material that survived was robust enough to do so. The more fragile molecules however were always destroyed and thus missing from meteorites, even though it was very clear from spectroscopy of these asteroids in the solar system that such molecules did exist, and likely formed the majority of these asteroids’ make-up.

Thus, though carbonaceous chondrite asteroids represent the early solar system, our understanding of them was warped and very incomplete. The whole point of both missions to Bennu and Ryugu was to fill in this data, to get a more complete census of the real make-up of the early solar system.

The two papers published this week have given us that. That’s their real discovery.
» Read more

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Scientists: most asteroids come from a limited number of earlier break-ups

10:04 am

According to three different recently published papers (available here, here, and here), the majority of all meteorites hitting the Earth likely came from a limited number of specific past break-ups of larger asteroids.

New studies show that 70% of the 70,000 meteorites that have been found on Earth have come from 3 recent collisions in the main asteroid belt which sits between the orbits of Mars and Jupiter. The collisions occurred 5.8, 7.5 and 40 million years ago, according to the studies. They correspond to 3 young asteroid “families” known as Karin, Koronis and Massalia. These families formed from the destruction of asteroids at least 30km across.

The 70% number comes from data in the last two papers above, while the first paper claims it is more like 80% of all asteroids. The Massalia family is the most dominate, with it estimated to be the source 37% of all meteorites as well as a major impact half a billion years ago.

The first study also found that both Ryugu and Bennu came from the same event and are part of another family of asteroids called Polana.

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Scientists try to model what would happen if Ryugu hit Earth

9:19 am

Ryugu's northen hemisphere
Ryugu’s northen hemisphere. The arrow marks the spot Hayabusa-2
gathered samples

Scientists, using the data and rock samples gathered by the Japanese probe Hayabusa-2, have attempted to predict what what would happen if the rubble-pile asteroid Ryugu hit the Earth.

Without diversion intervention, Tanaka explained, if the Ryugu asteroid was heading to Earth and entered the planet’s atmosphere at an angle of 45 degrees and at a speed of around 38,000 miles per hour (17 kilometers per second), the rubble pile asteroid would break up at an altitude of around 25 to 21 miles (40 to 35 km) over the surface of the planet.

This would result in an “airburst” similar to that seen over Russia in February 2013 when the Chelyabinsk meteor erupted at an altitude of around 19 miles (30 kilometers) over Earth. The result of the Chelyabinsk blast was a bright flash of light and an atmospheric blast equivalent to the detonation of 400–500 kilotons of TNT. This is as much as 33 times the energy released by the atomic bomb that devastated Hiroshima at the end of the Second World War.

The Chelyabinsk meteor caused about 1,500 injuries, mostly from people injured by glass thrown out by breaking windows when it suddenly and unexpectedly exploded during re-entry. With Ryugu this would not be a surprise, so these injuries could be reduced, though not eliminated. The damage and injuries from pieces that survived the breakup and hit the ground remains unknown because scientists don’t know how much of the asteroid would survive the break up.

Ryugu of course poses no threat, because it is not on a collision course with Earth. Whether an asteroid like Ryugu could be diverted however remains unknown, since any such diversion must not cause the asteroid to break apart as well.

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Samples from Ryugu found to contain uracil, one of the four nucleobases in RNA

11:02 am

Japanese researchers analyzing the samples returned by Hayabusa-2 from the rubble-pile asteroid Ryugu have identified the molecule uracil, one of the four nucleobases that form the molecule RNA.

Hayabusa 2 collected 5.4 grams from two spots on Ryugu and delivered them to Earth on December 6, 2020. Early studies showed the samples contained many organic compounds. That led Oba’s group to analyze two 10-milligram samples using the same sensitive technique they had used earlier on meteorites. The technique can detect nucleic acid bases at levels down to parts per trillion in small samples.

Now, they report in Nature Communications that uracil is present at a level of parts per billion in both Ryugu samples. While this concentration is different than they’d previously found in meteorites, Oba says that might be because the parent bodies of the meteorites and of Ryugu underwent different levels of aqueous alteration and other processes. They also detected niacin (vitamin B3) as well as other organic molecules, but they didn’t find any other nucleobases.

RNA is formed from four nucleobases, uracil, adenine, cytosine, and guanine. To form DNA, the fundamental building block of life, uracil is replaced by thymine.

This data reinforces other data that suggests the formation of these essential molecules for life is relatively common and easy, at least in our solar system.

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Many carbon-based molecules identified in Ryugu samples

9:53 am

Researchers in Japan, Europe, and the U.S. have now identified many carbon-based molecules in the Ryugu samples brought back to Earth by Japan’s Hayabusa-2 asteroid probe. From their paper, published in Science yesterday:

We identified numerous organic molecules in the Ryugu samples. Mass spectroscopy detected hundreds of thousands of ion signals, which we assigned to ~20,000 elementary compositions consisting of carbon, hydrogen, nitrogen, oxygen, and/or sulfur. Fifteen amino acids, including glycine, alanine, and α-aminobutyric acid, were identified. These were present as racemic mixtures (equal right- and left-handed abundances), consistent with an abiotic origin. Aliphatic amines (such as methylamine) and carboxylic acids (such as acetic acid) were also detected, likely retained on Ryugu as organic salts.

The presence of aromatic hydrocarbons, including alkylbenzenes, fluoranthene, and pyrene, implies hydrothermal processing on Ryugu’s parent body and/or presolar synthesis in the interstellar medium. Nitrogen-containing heterocyclic compounds were identified as their alkylated homologs, which could have been synthesized from simple aldehydes and ammonia. In situ analysis of a grain surface showed heterogeneous spatial distribution of alkylated homologs of nitrogen- and/or oxygen-containing compounds.

The large number of carbon-based molecules is not unlike data from similar carbonaceous chondrite meteorites, though the differences appear to suggest Ryugu experienced chemical processes in connection with water during its lifetime.

Note for clarity: Organic molecules are not life. This is a term scientists use for any carbon-based molecule.

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Samples from Ryugu prove the truly delicate and long-lived nature of the rubble-pile asteroid

9:27 am

Two new studies of samples brought back from the rubble-pile asteroid Ryugu by the Japanese probe Hayabusa-2 have found that the asteroid not only was never heated above 86 degrees Fahrenheit, it also contained dust grains older than the solar system itself.

The evidence from the first study, completed by Japanese scientists, suggested that:

  • 1.Asteroid Ryugu accreted some components that originated in the outer Solar System and contained abundant water and organics. The asteroid then traveled to the inner Solar System.
  • 2.Organics associated with coarse-grained phyllosilicates may serve as one of the potential sources of water and organics to the Earth.

The second study, using samples provided to American scientists, found two tiny dust grains that must have come from the material that existed before the formation of our solar system.

The team detected all the previously known types of presolar grains—including one surprise, a silicate that is easily destroyed by chemical processing that is expected to have occurred on the asteroid’s parent body. It was found in a less-chemically-altered fragment that likely shielded it from such activity.

This is not the first discovery of presolar grains, but their delicate existence in Ryugu confirms the conclusions of the first study, that Ryugu had to have formed in the outer solar system and then migrated inward over eons.

The second study also reviewed the make-up of the sample and concluded that Ryugu appears to most closely match the family of carbonaceous Ivuna-type (CI) chondrites, thought to be among the most primitive asteroids known, of which very few have been studied because of they rarely survive the journey through the Earth’s atmosphere.

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Amino acids found in asteroid samples brought back from Ryugu

10:01 am

Japanese scientists revealed this week that they have detected more than 20 types of amino acids in the asteroid samples brought back from Ryugu by the probe Hayabusa-2.

Kensei Kobayashi, professor emeritus of astrobiology at Yokohama National University, said the unprecedented discovery of multiple types of amino acids on an extraterrestrial body could even hint at the existence of life outside of Earth. “Proving amino acids exist in the subsurface of asteroids increases the likelihood that the compounds arrived on Earth from space,” he said.

It also means amino acids can likely be found on other planets and natural satellites, hinting that “life could have been born in more places in the universe than previously thought,” Kobayashi added.

Let me emphasize that this is not a discovery of life on Ryugu, only chemistry that is found in life on Earth. Such chemistry however can be found outside of life as well. What this detection suggests however that it is relatively common to produce such complex chemistry in hostile space environments, which increases greatly the possibility of life everywhere in the universe.

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Japanese scientists complete inventory of Ryugu asteroid samples

9:00 am

In a press conference yesterday the Japanese space agency JAXA announced that scientists have completed their inventory of the samples brought back from the asteroid Ryugu by the Hayabusa-2 spacecraft, and are now ready to begin distributing those samples to scientists around the world for more detailed research.

JAXA has cataloged the soil samples brought back by Hayabusa 2 last December, by size, color and shape. From now, 269 researchers from 14 countries, including Japan and the United States, will conduct an in-depth analysis of the soil’s structures and components over the course of about a year.

As expected, the inventory found the samples had a large amount of hydrogen, oxygen, and carbon atoms. Even before Hayabusa-2’s arrival, Ryugu had been catalogued as a “hydrated” asteroid, which means it was thought to contain a lot of hydrogen and oxygen, the basic elements of water. The inventory has now confirmed this.

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Ryugu’s most primitive boulders

1:18 pm

In a just published paper scientists reveal how they think they have identified the oldest rocks on the rubble pile asteroid Ryugu, and found them to be distributed across the entire face of the asteroid.

These boulders are light enough that they would float on water.

Ryugu is thought to have initially formed as a fluffy planetesimal that coalesced from accumulated dust in the early Solar System, and subsequently underwent processes such as thermal evolution and compression. This parent body was then later destroyed in a collision and fragments of this reaccumulated into the asteroid. However, planetesimals have never been seen, so whether they really existed or what they may have looked like is one of the biggest challenges in understanding the planet formation process. The boulders discovered in this research are thought to be a material that most strongly retains the appearance of the fluffy planetesimals that triggered the birth of the planets in the Solar System.

Additionally, the data from all the scientific instruments onboard Hayabusa2 that were used to examine the surface of Ryugu revealed that fragments of material similar to those of the ultra-high porosity boulders are globally distributed over the asteroid surface, and may have been collected in the sample taken by Hayabusa2. If highly primitive material with the ultra-high porosity discovered here is also found in the collected samples, it will both clarify the formation and evolutional history of Ryugu’s parent body, and also provide evidence of planetesimal formation in the early stage of the Solar System formation process.

There is no word yet from the scientists studying the Hayabusa-2 samples on what they have found. This paper gives them an idea of what could be the most important type of rock to look for.

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Hayabusa-2 begins journey to two asteroids

7:59 am

On January 5, 2021, after successfully delivering its samples of Ryugu to Earth, Hayabusa-2 fired up its ion engines and began its ten-year journey to two different asteroids.

Hayabusa2’s first extended-mission destination is the roughly 2,300-foot-wide (700 meters) asteroid (98943) 2001 CC21, which the probe will fly by at high speed in 2026, if all goes according to plan. A more in-depth rendezvous with yet another space rock, 1998 KY26, is scheduled to follow in 2031.

In a previous post I had mistakenly left out the first target asteroid. However, their primary target remains the tiny 100-foot-wide 1998 KY26, since it is so small. This will be the first close-up view of such a small asteroid, in space. Since such asteroids are many, it will tell us much about the make-up and history of the solar system.

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First look at Ryugu samples

8:55 am

Japanese scientists have taken their first look at the Ryugu sample material brought back by Hayabusa-2 and found they resemble charcoal.

The samples Japanese space officials described Thursday are as big as 1 centimeter (0.4 inch) and rock hard, not breaking when picked up or poured into another container. Smaller black, sandy granules the spacecraft collected and returned separately were described last week.

…The sandy granules the Japan Aerospace Exploration Agency described last week were from the spacecraft’s first touchdown in April 2019.

The larger fragments were from the compartment allocated for the second touchdown on Ryugu, said Tomohiro Usui, space materials scientist. To get the second set of samples in July last year, Hayabusa2 dropped an impactor to blast below the asteroid’s surface, collecting material from the crafter so it would be unaffected by space radiation and other environmental factors.

Usui said the size differences suggest different hardness of the bedrock on the asteroid. “One possibility is that the place of the second touchdown was a hard bedrock and larger particles broke and entered the compartment.”

The analysis of these samples has only just begun. Dating them is likely next, and that will probably reveal some startling results.

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Samples from space!

9:16 am

Scientists from both the Japanese Hayabusa-2 mission to the asteroid Ryugu and the Chinese Chang’e-5 mission to the Moon announced yesterday the total amount of material they successfully recovered.

The numbers appear to diminish the Japanese success, but that is a mistake. Getting anything back from a rubble-pile asteroid that had never been touched before and is much farther away from Earth than the Moon was a very great achievement. The 5.4 grams is also more than fifty times the minimum amount they had hoped for.

This is also not to diminish the Chinese achievement, They not only returned almost four pounds, some of that material also came from a core sample. They thus got material both from the surface and the interior of the Moon, no small feat from an unmanned robot craft.

Scientists from both nations will now begin studying their samples. Both have said that some samples will be made available to scientists from other countries, though in the case of China it will be tricky for any American scientist to partner with China in this research, since it is by federal law illegal for them to do so.

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Scientists confirm ample Ryugu material in first Hayabuse sample chamber

8:01 am

Japanese scientists have opened the first chamber that stored the Ryugu asteroid samples obtained during its first touch-and-go sample grab, and confirmed that it holds ample material.

They also noted that the chamber itself contained gas from the asteroid as well.

The Japan Aerospace Exploration Agency (JAXA) has confirmed that the gas collected from the sample container inside the re-entry capsule of the asteroid explorer, Hayabusa2, is a gas sample originating from asteroid Ryugu.

The result of the mass spectrometry of the collected gas within the sample container performed at the QLF (Quick Look Facility) established at the Woomera Local Headquarters in Australia on December 7, 2020, suggested that the gas differed from the atmospheric composition of the Earth. For additional confirmation, a similar analysis was performed on December 10 – 11 at the Extraterrestrial Sample Curation Center on the JAXA Sagamihara Campus. This has led to the conclusion that the gas in the sample container is derived from asteroid Ryugu.

They think that this gas must have outgassed from the samples themselves. I suspect it was released either during the long journey or when the samples were subjected to the high accelerations and impact during its return to Earth. Research is going to have to try to pin this down, however.

They plan to open the two remaining sample chambers containing material sometime next week.

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Scientists confirm Hayabusa-2’s return capsule brought back material from Ryugu

8:56 am

Based on their first observations of the return capsule from Hayabusa-1, Japanese scientists yesterday confirmed that it successfully has returned material from the asteroid Ryugu.

JAXA said in a statement that they observed the sandy material at the entrance of the collection chamber, but have yet to look inside to see if more asteroid dust is lurking there. It is only the second time that scientists have returned material from an asteroid.

This find in the entrance portends a gold mine of material in the collection chamber itself.

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Hayabusa-2’s samples from Ryugu land in Australia

2:07 pm

The return capsule carrying the asteroid samples grabbed by Hayabusa-2 from Ryugu successfully parachuted down in the outback of Australia today.

Officials from the Japan Aerospace Exploration Agency, or JAXA, confirmed shortly after 1 p.m. EST (1800 GMT) that the Hayabusa 2’s nearly 16-inch (40-centimeter) sample carrier landed in Australia. Touchdown likely occurred several minutes earlier.

Recovery teams dispatched via helicopter began hunting for the 35-pound (16-kilogram) capsule using estimates of its landing site derived from a radio beacon signal. Mission managers expected it could take several hours to find the capsule and recover it. The landing occurred before dawn in Australia.

Since the article above was posted the capsule was located, and it was found much quicker than first expected.

This was the second sample return mission by the Japanese. The first, Hayabusa-1, successfully returned its capsule in 2010, but because of many technical problems during the mission it only brought back a few microscopic samples. In fact, the technical problems were so bad it was really a miracle the capsule came back at all.

Hayabusa-2 however has been a complete success, showing that they learned from the first mission and applied those lessons to the second.

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Hayabusa-2’s impactor shook Ryugu

8:26 am

When Hayabusa-2 fired an impactor into the asteroid Ryugu in order to access subsurface material in a sample grab, it apparently shook the asteroid, shifting boulders and rocks as far as 130 feet away.

The artificial impactor disturbed boulders within a 30m radius from the center of the impact crater- providing important insight into asteroids’ resurfacing processes.

Professor ARAKAWA Masahiko (Graduate School of Science, Kobe University, Japan) and members of the Hayabusa2 mission discovered more than 200 boulders ranging from 30cm to 6m in size, which either newly appeared or moved as a result of the artificial impact crater created by Japanese spacecraft Hayabusa2’s Small Carry-on Impactor (SCI) on April 5th, 2019. Some boulders were disturbed even in areas as far as 40m from the crater center. The researchers also discovered that the seismic shaking area, in which the surface boulders were shaken and moved an order of cm by the impact, extended about 30m from the crater center. Hayabusa2 recovered a surface sample at the north point of the SCI crater (TD2), and the thickness of ejecta deposits at this site were estimated to be between 1.0mm to 1.8cm using a Digital Elevation Map (DEM).

This data makes all the more important for OSIRIS-REx to get post-sample-grab images of its Nightingale site, if at all possible.

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Ryugu, like Bennu, appears to have rocks from other asteroids

9:21 am

Japanese scientists today announced that 21 rocks identified by Hayabusa-2 on the asteroid Ryugu have a composition that suggests they were formed on another asteroid.

Although Ryugu’s surface is uniformly dark [because it is a C-type asteroid], the scientists behind the new research found numerous boulders scattered across the asteroid that were 1.5 or more times brighter than their surroundings — that is, they reflected at least 50% more light than most of the rest of Ryugu. This contrast made the researchers suspect these boulders may have come from outside the asteroid.

By analyzing the spectrum of light reflected off 21 of these boulders, the scientists deduced they were made of minerals known as anhydrous silicates. Prior studies have suggested that such water-poor, silicon-rich rocks make up silicaceous or S-type asteroids, the most common kind of asteroid found in the inner main asteroid belt. The brightness of these boulders also matches the brightness of S-type asteroids.

This result compliments the result yesterday from scientists studying Bennu with OSIRIS-REx, and was in fact released at the same time. Both asteroids apparently contain material from other asteroids, suggesting that asteroids in their initial formation (as rubble piles) are routinely a mixture of material from many asteroids, thrown out during impacts and then recaptured.

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Hayabusa-2’s future asteroid targets

10:02 am

Link here. There are two prime candidate asteroid targets, both near Earth astroids.

The possible secondary targets include the oblong asteroid 2001 AV43 or the asteroid 1998 KY 26. They’re each about the size of a large house and both orbit the Sun in roughly 500 days. The proposed plan would see Hayabusa 2 arriving at 2001 AV43 in the late 2029 time frame, or reaching 1998 KY 26 in July 2031. Both asteroids have a low enough relative speed relative to the spacecraft to put them within (eventual) reach after Hayabusa 2’s December flyby.

Interestingly, 2001 AV43 will fly 313,000 km from Earth (0.8 times the Earth-Moon distance) on November 11, 2029.

The two asteroids were selected from an initial field of 354 candidates, which was winnowed down based on accessibility and scientific interest. Both are fast rotators, as evidenced by their light curves, each spinning on its respective axis once every 10 minutes. This represents the shortest “day” of any known object in the solar system, suggesting that these asteroids are in fact solid objects and not simply loosely aggregated “rubble piles.” A visit to one of these asteroids would mark the first time a space mission has seen such an enigmatic fast rotator up close.

The asteroid 1998 KY26 is also a possible carbonaceous (C-type) asteroid, and Hayabusa 2’s exploration of such a space rock would be another first.

Going to 1998 KY26 would also require a distant pass of another asteroid. Going to 2001 AV43 would require a fly-by of Venus, which could provide more data on that planet. Based on this information, my guess is that they will opt for 1998 KY26.

The decision must likely be made before Hayabusa-2 drops off its Ryugu samples to Earth on December 6, 2020.

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Evidence suggests Ryugu was once closer to Sun

11:38 am

The uncertainty of science: Spectral data collected of the surface of Ryugu by Japan’s Hayabusa-2 probe suggests that the asteroid once spent a period of time much closer to the Sun.

The combined data show an oddly striated world. Ryugu’s equator and poles are tinged blue and are brighter compared with its darker, reddish mid-latitudes. These color differences wouldn’t be obvious to the human eye, although the brightness changes might be.

…As Tomokatsu Morota (University of Tokyo) and colleagues write in the May 8th Science, Ryugu’s boulders likely start bluish. Then a combination of solar wind exposure, meteoroid impacts, and solar heating reddens them. This redder stuff migrates to the asteroid’s mid-latitudes over time, because topographically those are the lowest on Ryugu’s surface. That movement leaves the higher equator and polar regions relatively bluer and brighter.

Based on this data, the scientists posit that Ryugu was closer to the Sun from 800,000 to 8 million years ago, and that the evidence also suggests that the asteroid is only at most 17 million years old.

To put it mildly, there are great uncertainties to these conclusions.

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OSIRIS-REx bypasses laser altimeter issue

1:40 pm

The science team for OSIRIS-REx has figured out a bypass for the failure of one of the spacecraft’s laser altimeters, originally used during close flyovers of the surface of the rubble-pile asteroid Bennu.

The mission has made the decision to use OLA’s High Energy Laser Transmitter (HELT) to provide the ranging data to focus PolyCam during the Mar. 3 flyover of site Nightingale. OLA consists of two laser subsystems, the HELT and the Low-Energy Laser Transmitter (LELT). OLA’s LELT was originally scheduled to provide these data, however, as a result of the anomaly that occurred during the Recon B site Osprey flyover, the team has determined that the LELT system is no longer operable. Despite the LELT’s condition, the HELT system has continued to operate as expected, and will be used to focus PolyCam for the remaining reconnaissance passes.

According to Erin Morton, head of communications for OSIRIS-REx in the Principal Investigator’s Office, the failure of LELT will not impact the touch-and-go sample grab, presently scheduled for sometime in August.

We don’t need OLA [either the low or high energy transmitters] for the sample collection event. OLA’s main purpose was to collect the altimetry data needed to make topographical maps for the sample site decision. It successfully accomplished that last year – which means that the instrument has completed all of its primary mission requirements. OLA isn’t used for navigation.

Instead, they are using an autonomous system that compares previous high resolution images with images taken during descent. In addition, they have a lidar system available as well.

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Hayabusa-2 fires main ion engines for return to Earth

8:20 am

After spending two weeks testing its main ion engines just beyond the gravitational sphere of influence of the asteroid Ryugu, Japanese engineers today initiated full engine operation, beginning the spacecraft’s journey back to Earth.

Hayabusa-2 is expected to return to Earth space in December 2020, where it will release a small capsule containing the two samples it obtained of Ryugu will be released to land on Earth and be recovered. At that point, if Hayabusa-2 is still in good condition it will be available to send to other locations in the solar system.

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Hayabusa-2 begins journey back to Earth

9:32 am

The Hayabusa-2 science team has fired up the spacecraft’s ion engine to leave the asteroid Ryugu and began its begins journey back to Earth.

It will take about six days to exit the gravitational sphere of influence of Ryugu. During that time period they will be continually releasing real time images of the asteroid from the spacecraft’s navigation camera, as it slowly gets farther away.

In mid-December they will fire the spacecraft’s main engines for an arrival near Earth in late 2020. At that point the small return capsule holding the samples from Ryugu will separate and land in the Australian desert. Hayabusa-2, still operational, might then be given a new subsequent mission.

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Hayabusa-2 to begin return voyage on November 13

8:08 am

In a press conference today the science team for the asteroid probe Hayabusa-2 announced that the spacecraft will begin the first stage of its journey back to Earth tomorrow, using its ion engine to slowly pull away from Ryugu.

That first stage will take a little less than a week. Once the spacecraft gets about 25 miles from Ryugu it will leave its sphere of gravitational influence, when it will then begin its cruise phase back to Earth.

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Bennu & Ryugu: Two very old and strange asteroids

5:35 pm

Bennu as seen by OSIRIS-REx
Bennu’s equatorial ridge. Click for full image.

This week the science team operating the OSIRIS-REx spacecraft at the asteroid Bennu hosted a joint conference in Tucson, Arizona, with the scientists operating the Hayabusa-2 spacecraft at the asteroid Ryugu. Both gave up-to-date reports on the science so far obtained, as well as outlined upcoming events. I was fortunate enough to attend.

First an overview. Both Bennu and Ryugu are near earth asteroids, with Bennu having an orbit that might even have it hit the Earth in the last quarter of 2100s. Both are very dark, and are rubble piles. Both were thought to be of the carbonaceous chondrite family of asteroids, sometimes referred to as C-type asteroids. This family, making up about 75% of all asteroids, includes a bewildering collection of subtypes (B-types, F-types, G-types, CI, CM, CV, CH, CB, etc), all of which were initially thought to hold a lot of carbon. We now know that only a few of these categories, the CI and CM for example, are carbon rich.

Even so, we actually know very little about these types of asteroids. They are very fragile, so that any that reach the Earth’s surface are not a good selection of what exists. About 90% of the material gets destroyed in the atmosphere, with the remnant generally coming from the innermost core or more robust nodules. We therefore have a biased and limited sample.

It is therefore not surprising that the scientists are finding that neither Bennu nor Ryugu resembles anything else they have ever seen. Both have aspects that resemble certain types of carbonaceous chondrite asteroids, but neither provides a very good fit for anything.
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