Current status on Mars exospheric studies

International audienceThe Martian exosphere is the collisionless region surrounding the Martian atmosphere. It is mainly composed of hydrogen and oxygen atoms. The hydrogen and oxygen atoms are produced in the Martian mesosphere-thermosphere from molecular dissociation and reach the exobase by vertical diffusion. A small part of these atoms reaching the exobase can escape into the interplanetary medium leading to a net loss of water. Another part does not escape but populates the exosphere forming an extended corona. In this presentation, we will present results of new models we developed in the frame of the HELIOSARES project to study the Martian exospheric hydrogen and oxygen populations. We will also present a comparison between these results and recent observations of the Martian exosphere done by Mars Express, Hubble Space Telescope and Rosetta