14:45 〜 15:00
[PPS04-05] Martian exosphere derived from pickup ion measurements: A feasibility study for future MMX mission
★Invited Papers
キーワード：火星、ピックアップイオン、外気圏、MMX、MAVEN
The Martian Moons eXploration (MMX) spacecraft will carry multiple scientific instruments to investigate Mars and its moon environments and return samples from Phobos. One of the instruments is the Mass Spectrum Analyzer (MSA) that measures ion velocity distributions and magnetic fields. The high mass resolution (M/ΔM>100) of MSA will allow us to study ion isotopes such as 18O+ and 13C+ as well as their major ion elements (16O+ and 12C+).
We conducted a feasibility study for future MMX/MSA observations of Martian upper atmosphere using the SupraThermal And Thermal Ion Composition (STATIC) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Analyzing the O+ pickup ion ring distributions in the solar wind and magnetosheath observed by STATIC, we established a method to retrieve distribution of hot oxygen corona around Mars. Using measured ion fluxes in the initial phase of the O+ ring distribution (i.e., the first quadrant part of the ring), we successfully retrieved ionization locations and number densities of hot oxygen atoms and obtained their number density distributions in ~1000-10000 km altitude ranges for various solar zenith angles and local times. We found that the retrieved hot O distributions reasonably agreed with previous observations. We also found that our method can retrieve the hot O distributions above ~6000 km altitude, using measurements near the Phobos orbit where MMX will fly in the future.
Utilizing our retrieval method in the future observations of MMX/MSA, we aim to retrieve Martian exospheric number density profiles of various exospheric components, including isotopes, with the MSA's pickup ion measurements around Phobos. Such information will be crucial for understanding the evolution history of Mars via atmospheric escape.
We conducted a feasibility study for future MMX/MSA observations of Martian upper atmosphere using the SupraThermal And Thermal Ion Composition (STATIC) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Analyzing the O+ pickup ion ring distributions in the solar wind and magnetosheath observed by STATIC, we established a method to retrieve distribution of hot oxygen corona around Mars. Using measured ion fluxes in the initial phase of the O+ ring distribution (i.e., the first quadrant part of the ring), we successfully retrieved ionization locations and number densities of hot oxygen atoms and obtained their number density distributions in ~1000-10000 km altitude ranges for various solar zenith angles and local times. We found that the retrieved hot O distributions reasonably agreed with previous observations. We also found that our method can retrieve the hot O distributions above ~6000 km altitude, using measurements near the Phobos orbit where MMX will fly in the future.
Utilizing our retrieval method in the future observations of MMX/MSA, we aim to retrieve Martian exospheric number density profiles of various exospheric components, including isotopes, with the MSA's pickup ion measurements around Phobos. Such information will be crucial for understanding the evolution history of Mars via atmospheric escape.