Effects of the June 2018 Global Dust Storm on the Atmospheric Composition of the Martian Upper Atmosphere as Observed by MAVEN

The densities of six neutral species in the Martian upper atmosphere were analyzed before and during the 2018 Martian global dust storm (GDS 2018) using data from the Neutral Gas and Ion Mass Spectrometer of the Mars Atmosphere and Volatile EvolutioN mission. The trends of the dayside densities of the neutral species and their relative abundances were investigated between May 27 and June 17, 2018, at altitudes of 160–210 km. GDS 2018 caused variations in the neutral species abundance of the upper atmosphere at its onset in June 5–8, 2018, with the CO₂, Ar, CO, O, N₂, and He densities decreasing relative to prestorm conditions. The densities of the examined neutral species increased during the storm, except those of O and He. During the storm, the relative abundances of CO₂ and Ar increased, while those of CO and O decreased and those of N₂ and He remained the same. The variation in the neutral species with altitude was consistent with the regular atmospheric conditions and unrelated to the GDS 2018 drivers. The higher thermospheric temperature observed during the storm onset suggested that changes in the composition of the neutral species were caused by storm-induced thermal enhancements.