Feb 11, 2022

Pebbles flying over Ryugu and returned grains


Overview of the press release

Analysis of returned samples is distinct from the analysis of meteorites because of the presence of geological information about the parent asteroid. However, can we expect to obtain valuable information that will lead to an understanding of the entire asteroid from samples gathered from limited areas? In light of these concerns, the team decided to run a full information analysis in which observations of the asteroid on different length scales (multi-scale) from the global appearance of the asteroid down to the millimeter sized particles in the return sample were analysed and compared. In this study, we combined the results of multi-scale observations of Ryugu surface particles by CAM-H during the spacecraft touchdowns, the observations made by the MINERVA-II1 hopping rovers at multiple locations across the asteroid, and the return samples in the clean chamber. We found that the return samples well represent Ryugu surface particles and that there are characteristic flat and elongated particles on the asteroid. In addition, CAM-H images showed that the sampler system correctly operated to collect and return 5 grams of samples.
The particles brought back are now being analyzed in the laboratory down to the atomic level. The mission aims to unravel the 4.6 billion-year-long Solar System history over a spatial scale of billions of kilometers by synthesizing the results from multi-scale observations. In particular, the spacecraft-returned samples are different from extraterrestrial materials recovered on the ground (i.e. meteorites) because the returned samples are obtained with geological information after the spacecraft clarifies the nature of the target object. Ryugu samples will therefore tell us what elements and materials constitute C-type asteroids.

They published their results on Feb. 10 in Science.

Figure : (Left and center) CAM-H images taken 2 and 3 seconds after the first touchdown, showing particles with arrows flying toward CAM-H from the bottom of the sampler horn. (Right) CAM-H image taken 2 seconds after the second touchdown, showing that the particles with white arrows are cm in size based on the shadows on the rocket coupling ring (credit: JAXA).


Professor Shogo Tachibana (UTokyo Organization for Planetary and Space Science), Professor Seiji Sugita, Associate Professor Tomokatsu Moroda, Assistant Professor Yuichiro Cho and Doctoral Student Koki Yumoto (Department of Earth and Planetary Physics, Graduate School of Science, UTokyo), contributed to this research.

To read the full press release, please visit the website of the Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA).


Publication details

Journal  Science
 Pebbles and sand on asteroid (162173) Ryugu: in situ observation  
 and particles returned to Earth
 Shogo Tachibana, et al.



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