- 3645 - RYUGU - sample from asteroid returns? On December 6, 2020, 5.4 grams of material from the near-Earth asteroid “162173 Ryugu” was returned to Earth on the Japanese space craft, “Hayabusa 2“.
--------------------- 3645 - RYUGU - sample from asteroid returns?
- The discoveries from these asteroid rock samples alter our understanding of what Ryugu looks like. The diamond-shaped space rock is both darker and more porous than expected. This fragility is important in terms of assessing whether it or similar asteroids could one day threaten Earth.
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- The asteroid’s rocks also contain volatile compounds, suggesting Ryugu preserves material from the outer Solar System. This means scientists now have in their labs some of the most pristine stuff from the Solar System’s infancy. This is a time capsule from before the beginning of our world.
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- The Ryugu sample reflects just 2 percent of the light it receives. It is exceptionally fragile. It is about 50 percent more porous than carbonaceous chondrite meteorites that have fallen to Earth.
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- Such high-micro-porosity materials have not been discovered in any meteorites found on Earth probably due to break-up owing to their fragile nature during entry into the Earth’s atmosphere.
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- The Hayabusa 2 spacecraft is the second-ever mission to return samples of an asteroid to Earth. The compositional analysis of Ryugu samples was made by the “MicrOmega hyperspectral microscope” chemical analysis.
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- The asteroid rock contains a wide variety of volatile organic compounds, including non-water molecules made of oxygen and hydrogen atoms known as “hydroxyls“. These volatiles likely originated in the outer Solar System. These Ryugu samples appear to be among the most primordial materials available in our laboratories.
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- The Hayabusa 2 craft launched on a nearly four-year mission to Ryugu in December 2014, arriving at the asteroid in June, 2018.
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- Ryugu is a C-type, or “carbonaceous” asteroid. These are asteroids that contain large portions of carbon and are the most common asteroid type in the Solar System. It’s a member of the “Apollo group“, near-Earth asteroids with orbits ranging from just outside Earth’s to inside our planet’s orbit, crossing Earth’s orbit during their trip around the Sun.
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- Hayabusa 2 collected surface and subsurface material from the asteroid in late 2019. It dropped the samples to Earth on December 3, 2020. Hayabusa 2 continued on for an extended mission to another near-Earth “Apollo asteroid, 1998 KY26“.
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- Researchers began the of nondestructive analysis of the Ryugu samples, using spectrographs and optical microscopes to probe the dust for clues to some of the biggest questions we have about our Solar System.
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- Asteroids like Ryugu represent unique archives from the early days of the Solar System, material kept in a deep freeze, and unchanged, from the time before planets formed.
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- The Ryugu sample is the second of its kind ever returned to Earth. The first arrived in 2005 when the Japan Aerospace Exploration Agency mission Hayabusa managed to return a few micrograms of dust from the near-Earth asteroid “25143 Itokawa“.
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- Until NASA’s “ORISIS-Rex” returns with its samples of the near-Earth asteroid “101955 Bennu”in 2023, these are the only samples we have.
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- Because reflectance spectra and colors of surface rocks on Bennu look different from those of Ryugu, we expect different kinds of samples will be returned from Bennu.
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- The Bennu samples constitute a uniquely precious collection which are now available for refined laboratory analyses with the potential to draw new insights into the formation and evolution paths of planetary bodies in our Solar System.
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- At least some near-Earth asteroids that cross our path around the Sun may be too spongy and fragile to survive entering Earth’s dense atmosphere and remain intact enough to cause tremendous damage on impact.
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- Asteroid Bennu is a member of the Apollo group like Ryugu, Bennu is a B-type asteroid, with a more blue spectrum and likely a very different composition than Ryugu. Bennu also has a one in 1,800 chance of hitting Earth sometime in the 2100s.
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- C-type asteroids are considered to be primitive small Solar System bodies enriched in water and organics, providing clues to the origin and evolution of the Solar System and the building blocks of life.
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- Laboratory analysis of returned samples is invaluable to determine the fine properties of asteroids and other planetary bodies. Samples from Ryugu discovered the particle size distribution, density and porosity, spectral properties and textural properties.
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- The sample consisted of rugged and smooth particles of millimeter to submillimeter size, confirming that the physical and chemical properties were not altered during the return from the asteroid.
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- The power index of its size distribution is shallower than that of the surface boulder observed on Ryugu11, indicating differences in the returned Ryugu samples. The average of the estimated bulk densities of Ryugu sample particles is 1,282 ± 231 kg /m^3, which is lower than that of meteorites, suggesting a high microporosity down to the millimeter scale, extending centimeter-scale estimates from thermal measurements.
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- The extremely dark optical to near-infrared reflectance and spectral profile with weak absorptions at 2.7 and 3.4 micrometer imply a carbonaceous composition with indigenous aqueous alteration, matching the global average of Ryugu.
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- The characterization of objects that have best preserved the mineralogical and molecular phases formed in the earliest stages of the Solar System evolution is key to understanding the processes that led to the formation of the planets in their diversity.
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- The occurrence of volatile-rich species, likely originating from the outer Solar System, would support Ryugu having preserved both pristine material and altered phases, which are now available for refined laboratory analyses with the potential to draw new insights into the formation and evolution paths of planetary bodies in our Solar System.
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August 7, 2022 RYUGU - sample from asteroid returns? 3631
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