Water Escape from Mars During the June 2018 Global Dust Storm
Résumé
The martian exosphere has been observed to undergo substantial dynamical changes as Mars approaches perihelion in its orbit around the Sun. Both hydrogen and deuterium escape, tied to water and atmospheric escape from Mars, show significant variations with the peak escape occurring close to martian southern summer solstice (solar longitude Ls = 270°). These changes are theorized to be brought about by atmospheric heating due to increase in dust in the atmosphere of Mars in combination with seasonal effects. Dust storm season at Mars is prevalent between solar longitude Ls = 180° - 330°. It is difficult to separate the effects of dust in the atmosphere of Mars from seasonal changes. The 2018 global dust storm presented a unique opportunity to study the effects of substantial amounts of dust in the martian atmosphere on water/atmosphere escape. The onset of the dust storm occurred when Mars was at Ls = 186°, far from southern summer solstice where the seasonal effects reach their peak. Lyman α photons from hydrogen and deuterium atoms present in the martian exosphere were observed with the MAVEN-IUVS Echelle spectrograph and the Hubble Space Telescope (HST). We will present the results of these observations and provide insight into the effects of a martian global dust storm on the atmospheric/water escape from Mars.