[M-IS20] 水惑星学

[MIS20-P04] Transport processes of dust and water in the Martian atmosphere to be revealed by MIRS onboard the MMX mission

*中川 広務¹、青木 翔平²、小郷原 一智³、今村 剛²、Thomas Gautier⁵、Aymeric Spiga⁶、Tanguy Bertrand⁷、Franck Montmessin⁵、Alain Doressoundiram⁷、Jeremie Lasue⁸、風間 暁¹、笠羽 康正¹、寺田 直樹¹、Eric Sawyer⁹、Maria Antonietta Barucci⁷、Jean-Michel Reess⁷、Pernelle Bernardi⁷、Sonia Fornasier⁷、岩田 隆浩⁴ (1.東北大学　大学院理学研究科、2.東京大学　新領域創成科学研究科、3.京都産業大学　理学部、4.宇宙航空研究開発機構　宇宙科学研究本部、5.Laboratoire Atmospheres and Space Observations (LATMOS), Planetary Science Department、6.Laboratoire de Meteorologie Dynamique / Institut Pierre-Simon Laplace (LMD/IPSL), Sorbonne Universit、7.Paris Observatory LESIA、8.Observatoire Midi-Pyrenees - Universite Paul Sabatier Institut de Recherche en Astrophysique et Planetologie、9.Centre National d'etudes Spatiales)

キーワード：火星、MMX、大気、赤外分光、水、ダスト

The MMX infrared spectrometer (MIRS) is an imaging spectrometer onboard MMX JAXA mission. MMX (Martian Moon eXploration) (Kuramoto et al. 2022, EPS 74, 12) is scheduled to be launched in 2024 with sample return from Phobos to Earth in 2029. MIRS will remotely provide near-infrared (IR) spectral maps in the spectral range from 0.9 to 3.6 micron with a spectral resolution better than 20 nm for Martian atmosphere, in addition to those of Phobos and Deimos. The previous observations of the lower atmosphere have been mostly done by polar-orbiting spacecrafts, such as Mars Global Surveyor (MGS), Mars Express (MEX), and Mars Reconnaissance Orbiter (MRO). These observations have provided global pictures of the atmospheric species and aerosols distributions at the Martian atmosphere at (mostly) fixed local times. Thus, development and decay of mesoscale to synoptic scale atmospheric events (such as horizontal water transport including surface-atmosphere interaction, clouds formation, and dust storms, etc.) have remained unclear. The more recent TGO and EMM mission already improved this coverage allowing different local times to be probed but still limited for continuous monitoring to track the variability of atmospheric phenomena. The equatorial orbit of MMX can offer some advantages for global mapping of the Martian atmosphere, as done by EMM. Being placed on the same orbit as Phobos around Mars, at altitudes 6000 km, the spacecraft will have a 7 hr orbit around Mars, allowing to complete a global mapping of Mars. The well-controlled scanner system of MIRS enables the specific pointing of the instrument, thus allowing MIRS measurements to obtain wide spatial coverage in hourly time-scale. The spacecraft’s slewing capabilities will also be used during observations of Mars in order to maximize the coverage of the MIRS from low to mid-latitudes within an hour, or to obtain almost global mapping of the sunlit hemisphere with several orbits, in combination with its scanner. These provide the first opportunity to follow the temporal evolution of the atmospheric species (CO2, H2O, CO) and aerosols (dust and clouds) with a mesoscale spatial resolution to reveal the rapid transport processes of the atmospheric species and aerosols with relatively high spatial resolution (typically 2.5~10.0 km). Such time-resolved pictures of the atmospheric phenomena should be an important clue to understand both the processes of water exchange between the surface/underground reservoirs and the atmosphere and the drivers of efficient material transport to the upper atmosphere.