NIRS3 spectral analysis of the artificial Omusubi-Kororin crater on Ryugu

A Galiano, E Palomba, F Dirri, A Longobardo, K Kitazato, T Iwata, M Matsuoka, T Hiroi, D Takir, T Nakamura, M Abe, M Ohtake, S Matsuura, S Watanabe, M Yoshikawa, T Saiki, S Tanaka, T Okada, Y Yamamoto, Y Takei, K Shirai, N Hirata, N Hirata, K Matsumoto, Y Tsuda

Monthly Notices of the Royal Astronomical Society, stac1547,

Published: 27 June 2022


“The JAXA Hayabusa2 mission accomplished the formation of an artificial crater on the asteroid Ryugu. The aim of this work is to analyse the area surrounding the artificial crater and reveal spectral variability compared to the same region before the crater formation, to mineralogically and physically characterize the subsurface exposed material. The crater’s investigation focused on the analysis of 2 regions corresponding to the inner part of crater (the pit and the crater wall/floor), 2 areas related to ejecta deposited close to the crater, 2 areas of ejecta moved far from the crater; 2 external areas. Each area was investigated both before and after the crater formation, by the study of the photometrically corrected spectral parameters: the 1.9 µm reflectance, the NIR spectral slope, the depth of the bands at 2.7 µm and at 2.8 µm. The subsurface material of the post-crater areas shows deeper absorption bands, a decrease in reflectance and a reddening in spectral slope with respect to the surface material of pre-crater areas. The subsurface regolith could have experienced a lower OH devolatilization due to space weathering and/or could be composed of finer dark grains than the surface layer. The ejecta reached distances of ∼20 m from the impact point, mainly moving in the northern direction; nevertheless, few ejecta also reached the south-eastern part of crater.”