[M-IS35] Why is this planet to be the Earth? -the role of water

[MIS35-03] Exploring the origin of Earth's water by the Hayabusa-2 near-infrared spectrometer

*Kohei KITAZATO¹, Takahiro IWATA², Masanao ABE², Makiko OHTAKE², Takahiro HIROI³, Tomoki NAKAMURA⁴, Mutsumi KOMATSU⁵, Tomoko ARAI⁶, Aiko NAKATO², Takahito OHSAWA⁷, Yusuke NAKAUCHI⁵, Sei-ichiro WATANABE⁸ (1.University of Aizu, 2.JAXA/ISAS, 3.Brown University, 4.Tohoku University, 5.Graduate University for Advanced Studies, 6.Chiba Institute of Technology, 7.JAEA, 8.Nagoya University)

Keywords:Hayabusa-2, asteroids, water, near-infrared spectroscopy

NIRS3, the near-infrared spectrometer onboard the Hayabusa-2 spacecraft, is a remote-sensing instrument to obtain the reflectance spectra including 3-μm absorption features due to structural OH ions and H2O molecules. In 2018-2019, we are planning to perform proximity observations of a near-Earth C-type asteroid 1999JU3 using NIRS3 and to reveal the distribution of hydrated minerals on the asteroid surface. Recently, the results indicating the presence of internal water ice for C-type asteroids were reported from ground-based observations. Hence, there is a possibility that the contribution of C-type asteroids to formation of Earth's ocean becomes larger than that predicted so far. It is required to understand the behavior of water in the aqueous alteration to verify the internal water ice. Thus, NIRS3 aims at obtaining information about the aqueous alteration discerning the secondary alteration effects such as thermal dehydration and space weathering from observations of the crater formed by the artificial impact experiment. In this presentation, we introduce the expected outcome of NIRS3 based on the current knowledge of C-type asteroids.