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Scientists offer first look at samples from asteroid Ryugu

They say the material — collected when a probe shot the asteroid with a copper cannonball — is some of the most primordial ever studied.

(CN) — The Japanese probe Hayabusa2 returned to Earth from the asteroid Ryugu a year ago with material believed to have originated during the early days of the solar system, and the first analysis of its valuable payload is now complete.

The Japanese Aerospace Exploration Agency, or JAXA, launched the probe in December 2014, and it spent 16 months orbiting the asteroid after arriving in the middle of 2018. Researchers had hoped to find new clues about the early history of the solar system — and it appears they may get their wish.

A team of scientists from Japan and France described the asteroid material and how it relates to the formation of the solar system in a study published Monday in the journal Nature Astronomy.

Ryugu is a C-type asteroid, which make up 75% of known asteroids in the solar system. C-type asteroids tend to be rich in ice and carbon and reflect very little light as evidenced by their dark color. Upon studying the samples returned from Ryugu, scientists confirmed the material is carbon-rich and reflects just 2% of the light shined on it — making it among the darkest naturally occurring materials known to exist. The material returned from Ryugu is also more porous than any meteorite studied to date, the scientists said.

“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,” the study authors wrote.

The majority of the samples have been preserved in the Extraterrestrial Samples Curation Center at the Institute of Space and Astronautical Science in Sagamihara, Japan, where they’re being carefully looked after and studied. JAXA also traded 10% of the material to NASA in exchange for samples from NASA’s OSIRIS-Rex spacecraft which is set to return to Earth in 2023 with its own payload of material from the asteroid Bennu.

The study authors performed mineralogical and molecular analyses on the material using a special microscope located in France that can view images at different wavelengths between the visible and infrared light spectrums. They found the material is composed mainly of clay with a variety of organic compounds contained within, along with bits and pieces of other substances such as carbonates and volatile compounds.

“The MicrOmega hyperspectral microscope developed at the Institut d'Astrophysique Spatiale (Orsay, France), which operates in the near-infrared range (0.99–3.65 µm), is performing their mineralogical and molecular characterization down to the scale of a few tens of micrometres,” the study authors wrote. “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.”

Hayabusa2 returned only the fourth sample ever retrieved from an extraterrestrial body. In addition to surface material, the Japanese team responsible for operating Hayabusa2 wanted to retrieve samples from below the surface of the asteroid, so they shot it with a copper cannonball which allowed another device to retrieve subsurface samples from the resulting crater. This novel technique provided researchers with valuable data which couldn’t have been gleaned by merely scooping up surface material.

“The Hayabusa2 returned samples, thus, appear to be among the most primordial materials available in our laboratories,” the authors concluded. “The samples constitute a uniquely precious collection, which may contribute to revisiting the paradigms of solar system origin and evolution.”

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