On the Origins of Mars' Exospheric Nonthermal Oxygen Component as Observed by MAVEN and Modeled by HELIOSARES. Issue 12 (4th December 2017)

• Record Type: Journal Article
• Authors: Leblanc, F.; Chaufray, J. Y.; Modolo, R.; Leclercq, L.; Curry, S.; Luhmann, J.; Lillis, R.; Hara, T.; McFadden, J.; Halekas, J.; Schneider, N.; Deighan, J.; Mahaffy, P. R.; Benna, M.; Johnson, R. E.; Gonzalez‐Galindo, F.; Forget, F.; Lopez‐Valverde, M. A.; Eparvier, F. G.; Jakosky, B.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 12(2017)
• Page Start: 2401
• Page End: 2428
• Publication Date: 2017-12-04
• Subjects: Mars' atmospheric escape -- MAVEN -- exosphere; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1002/2017JE005336
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: The first measurements of the emission brightness of the oxygen atomic exosphere by Mars Atmosphere and Volatile EvolutioN (MAVEN) mission have clearly shown that it is composed of a thermal component produced by the extension of the upper atmosphere and of a nonthermal component. Modeling these measurements allows us to constrain the origins of the exospheric O and, as a consequence, to estimate Mars' present oxygen escape rate. We here propose an analysis of three periods of MAVEN observations based on a set of three coupled models: a hybrid magnetospheric model (LATmos HYbrid Simulation (LatHyS)), an Exospheric General Model (EGM), and the Global Martian Circulation model of the Laboratoire de Météorologie Dynamique (LMD‐GCM), which provide a description of Mars' environment from the surface up to the solar wind. The simulated magnetosphere by LatHyS is in good agreement with MAVEN Plasma and Field Package instruments data. The LMD‐GCM modeled upper atmospheric profiles for the main neutral and ion species are compared to Neutral Gas and Ion Mass Spectrometer/MAVEN data showing that the LMD‐GCM can provide a satisfactory global view of Mars' upper atmosphere. Finally, we were able to reconstruct the expected emission brightness intensity from the oxygen exosphere using EGM. The good agreement with the averaged measured profiles by Imaging Ultraviolet Spectrograph during these three periods suggests that Mars' exospheric nonthermal component can be fully explained by the reactions of dissociative recombination of the O2 + ion in Mars' ionosphere, limiting significantly our ability to extract information from MAVEN observations of the O exosphere on other nonthermal processes, such as sputtering. Plain Language Summary: The first measurements of the emission brightness of the oxygen atomic exosphere by Mars Atmosphere and Volatile EvolutioN (MAVEN) mission have clearly shown that it is composed of a thermal component produced by the extension of the upper atmosphere and of a nonthermal component. Modeling these measurements allows us to constrain the origins of the exospheric O and, as a consequence, to estimate Mars' present oxygen escape rate. The good agreement between HELIOSARES set of models and the averaged measured profiles by IUVS during three periods of MAVEN measurements suggests that Mars' exospheric nonthermal component can be fully explained by the reactions of dissociative recombination of the O2 + ion in Mars' ionosphere, limiting significantly our ability to extract information from MAVEN observations of the O exosphere on other non‐thermal processes, such as sputtering. Key Points: A comparison between MAVEN and simulations show a global good agreement The main origin of the oxygen nonthermal component is from the dissociative recombination of O2 + in Mars' ionosphere Sputtering cannot be identified in MAVEN exospheric observation but might lead to local change that could be observed by MAVEN