[P-PS08] [JJ] 月の科学と探査

[PPS08-04] 月周回衛星「かぐや」による地球起源酸素イオンの観測

★招待講演

*寺田 健太郎¹、横田 勝一郎²、斎藤 義文²、北村 成寿²、浅村 和史²、西野 真木³ (1.大阪大学院理学研究科宇宙地球科学専攻、2.宇宙科学研究所、3.名古屋大学宇宙地球環境研究所)

キーワード：地球-月システム、月周回衛星「かぐや」、酸素、地球磁気圏、太陽風、地球風

Oxygen, the most abundant element of Earth and Moon, is a key element to understand the various processes in the Solar system, since it behaves not only as gaseous phase but also as the solid phase (silicates). Here, we report observations from the Japanese spacecraft Kaguya of significant 1-10 keV O⁺ ions only when the Moon was in the Earth’s plasma sheet. Considering the valence and energy of observed ions, we conclude that terrestrial oxygen has been transported to the Moon from the Earth’s upper atmosphere (at least 2.6 x 10⁴ ions cm^-2 sec^-1). This new finding could be a clue to understand the complicated fractionation of oxygen isotopic composition of the very surface of lunar regolith (particularly the provenance of a ¹⁶O-poor component), which has been a big issue in the Earth and Planetary science.