[P-PS08] 月の科学と探査

[PPS08-03] かぐや搭載スペクトロプロファイラ（SP）による高緯度領域データの解析：水氷の存在可能性の調査

經田 原弘³、*田中 智¹、大竹 真紀子¹、長岡 央²、仲内 悠祐²、小野寺 圭祐⁴ (1.宇宙航空研究開発機構宇宙科学研究所固体惑星科学研究系、2.宇宙航空研究開発機構、3.東京大学複雑理工、4.総合研究大学院大学)

キーワード：月、スペクトルプロファイラー、水氷

Recently, space agencies such as NASA and JAXA are actively planning to explore the polar region of the Moon since its usability as lunar base and possible existence of volatile elements([1],[2]). Landing site selection should be taken into consideration of the sunshine rate, existence of volatile materials in the vicinity [3], and so on. Therefore, geological and geomorphological studies in the polar region of the Moon have become more important. In this paper, we focused on detecting of water ice in the polar region using Spectral Proler(SP) data obtained by KAGUYA. Li et al.,(2018)[4] reported exposed water in the permanently shaded area by M³ data. It is possible to detect more distinct feature of water absorption by the SP data with high S/N ratio. Data analysis by the SP data in the polar region is still difficult due to the large solar incidence angle, however, we reported that the data could be handled with high-accuracy by estimation of insolation area for each spectrum using deep learning method [5]. Based on the SP data in the fully shaded area classied by the method above, we investigated the spectrum having absorption at 1260 nm and 1500 nm both of which are featured by ice and frost of water. As a result, we found about 300 spectrum data having distinct water absorption. One of the data with this absorption obtained in the middle of April, 2009 was located at around (lat. , lon.)=(-85, 50) at where Li et al., (2018) indicated the presence of water ice, but most of the data locations are not overlapped. Moreover, the solar incident angles of all selected data are too high to detect the direct nor the secondary reflected light from the surface of the target area. It is possible that the floating dust at a distance of several tens of kilometers the Moon originated from the impacts or levitation may have been detected[6].

References

[1] Heldmann et al., (2016) Acta Astronautica, 127, 308-320.
[2] Ivanov et al., (2015) Planetary and Space Science, 117, 45-63.
[3]Sanin et al., 2016, Icarus 283 20{30.
[4]Li et al., 2018, PNAS 115 (36) 8907-8912.
[5]Kyoda et al., 2018, 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).
[6]Wooden et al., 2016, Nature Geoscience volume 9, pages 665{668