First compositional analysis of Ryugu samples by the MicrOmega hyperspectral microscope

International audienceThe 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 Hayabusa2 mission of the Japan Aerospace Exploration Agency has returned for the first time samples collected at the surface of a C-type asteroid, Ryugu1,2. They are now preserved at the Extraterrestrial Samples Curation Center of the Japan Aerospace Exploration Agency at the Institute of Space and Astronautical Science in Sagamihara, Japan, where they are submitted to a first round of purely non-destructive analyses. 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. Strong features at 2.7 µm (indicating their OH-rich content) and at 3.4 µm (diagnostic of the presence of organics) dominate at a global scale, but key distinctive signatures have been identified at a submillimetre scale. In particular, carbonates (a fraction of them enriched in iron) as well as NH-rich compounds have been detected. 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