10:00 〜 10:15
[PPS09-05] Spatial distribution of low-energy ions originating from the lunar surface and exosphere: Preparation for MMX/MSA observations
キーワード：月、イオン、かぐや、MMX/MSA
The Martian Moons eXploration (MMX) spacecraft, scheduled for launch in 2026, will carry multiple scientific instruments to investigate Mars and its moons. One of these instruments is the Mass Spectrum Analyzer (MSA), which will measure ions originating from both the surface of Phobos and the Martian upper atmosphere. With its high mass resolution (M/ΔM > 100), MSA will help determine the elemental composition of Phobos’ surface, providing valuable insights into the moon’s origin.
MSA’s measurements will also be useful for the Landing Site Selection (LSS) activity. Since the LSS activity is time-constrained, it is crucial to be well-prepared for prompt data analysis once MMX begins its scientific observations. In this study, we analyze data obtained by the Ion Mass Analyzer (IMA) onboard the Kaguya spacecraft, which serves as the heritage for MSA, to prepare for future MSA observations. Specifically, we focus on analyzing low-energy ions originating from the lunar surface and exosphere.
Assuming that these low-energy ions are accelerated along the solar wind motional electric field, we can backtrace their trajectories to the field’s footprint and map their flux distribution on the lunar surface. Using approximately one year of data, we identified seven ion species (He+, C+, O+, Na+, Al+, K+, and Ar+) and found that their flux distributions exhibit a dawn-dusk asymmetry, with higher fluxes on the dawnside than on the duskside. This suggests that a phenomenon occurring preferentially on the dawnside may play a significant role in generating the lunar exosphere. In this presentation, we plan to present results examining the dependence of ion flux maps on solar wind conditions, solar flux, and meteor showers and discuss the cause of the observed dawn-dusk asymmetry. This analysis will help further explore the generation mechanisms of the lunar exosphere and associated ions.
MSA’s measurements will also be useful for the Landing Site Selection (LSS) activity. Since the LSS activity is time-constrained, it is crucial to be well-prepared for prompt data analysis once MMX begins its scientific observations. In this study, we analyze data obtained by the Ion Mass Analyzer (IMA) onboard the Kaguya spacecraft, which serves as the heritage for MSA, to prepare for future MSA observations. Specifically, we focus on analyzing low-energy ions originating from the lunar surface and exosphere.
Assuming that these low-energy ions are accelerated along the solar wind motional electric field, we can backtrace their trajectories to the field’s footprint and map their flux distribution on the lunar surface. Using approximately one year of data, we identified seven ion species (He+, C+, O+, Na+, Al+, K+, and Ar+) and found that their flux distributions exhibit a dawn-dusk asymmetry, with higher fluxes on the dawnside than on the duskside. This suggests that a phenomenon occurring preferentially on the dawnside may play a significant role in generating the lunar exosphere. In this presentation, we plan to present results examining the dependence of ion flux maps on solar wind conditions, solar flux, and meteor showers and discuss the cause of the observed dawn-dusk asymmetry. This analysis will help further explore the generation mechanisms of the lunar exosphere and associated ions.