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PSI in Iceland: Discussing Ryugu Sample Analyses with the Stone Team

In-person attendees, from left to right: Zelia Dionnet, Jean-Christophe Viennet, Mathieu Roskosz, Deborah Domingue, Camilo Jaramillo-Correa, Ashely King, Mizuha Kikuiri, Kana Amano, Tomoki Nakamura, Takashi Mikouchi

The asteroid (162173) Ryugu was visiting by JAXA/ISAS’s Hayabusa2 spacecraft, which touched down on its surface twice collecting samples. These samples were returned to Earth on December 6, 2020, and the large grains from both sample sites have been under examination by the Stone Team, an international group of sample scientists and researchers lead by Tomoki Nakamura from Tohoku University in Sendai, Miyagi Japan. The Stone Team gathered in a hybrid meeting, hosted in-person in Reykjavik Iceland August 22 – 24, 2022. PSI scientists Faith Vilas and Amanda Hendrix joined virtually while Deborah Domingue joined in person. This was part of their TREX/SSERVI work in support of the Stone Team’s Ryugu sample analyses. At the meeting they presented the status of their ultraviolet to near-infrared spectral analyses of sample grains and powders, which are currently being prepared for publication. Vilas and Hendrix led a unique experiment, analyzing single grains in the ultraviolet that have never been exposed to the Earth’s atmosphere. These measurements were performed at the University of Illinois Urbana-Champaign, a TREX partner, with the use of the Avantes spectral system from the PSI laboratory. While the spectral data are still be analyzed, the team is seeing that no two grains look alike spectrally!

Domingue has led the analysis of sample powders resulting from the physical tests of one of the largest grains collected by Hayabusa2. These powders were examined in the ultraviolet to the near-infrared (200nm – 2500 nm). While these powders have been exposed to Earth’s atmosphere, they provide an opportunity to examine the effects of atmospheric exposure and the effects of the inclusion of a fine-grained component to Ryugu’s regolith. Part of Domingue’s presentation was the comparison of the laboratory powder spectra with the surface spectra obtained by the Hayabusa2 spacecraft while hovering over the surface of Ryugu.

Left: sample container holding the Ryugu powder samples. Right: TREX analysis team Camilo Jaramillo-Correa and Deborah Domingue

With the meeting hosted in Iceland, Domingue took the opportunity to explore (a planetary scientist’s favorite pastime). Iceland is a volcanic island that is forming at the juncture of two continental plates (the North American and Eurasian plates) that are pulling apart. This means lot’s of processes associated with volcanism (geysers, sulfur springs, and of course, lava flows). It’s interesting to compare images of the surface of Ryugu taken by the MINNERVA-II lander and those of the more recent flows on Iceland.

Left: Image of Ryugu’s surface acquired by the Hayabusa2 Minerva-II rover (image credit: JAXA). Right: Lava flow near the coast, outside of Rekjavik. Credit: D. Domingue/PSI.
Oct. 2, 2022

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