Hot Oxygen and Carbon Escape from the Early Atmosphere of Mars

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Ute Amerstorfer1, Hannes Gröller2, Herbert Lichtenegger1, Helmut Lammer1 and Feng Tian3, (1)Space Research Institute, Austrian Academy of Sciences, Graz, Austria, (2)University of Arizona, Tucson, AZ, United States, (3)Tsinghua University, Beijing, China
Nowadays, the atmosphere of Mars is commonly assumed to be much different than in the early times of its evolution. Especially, the escape of water and carbon dioxide is thought to have formed its shape during millions of years. Also the Sun emitted a higher EUV flux in former times, influencing the particle environment around Mars.
We study the escape of oxygen and carbon from the early Martian atmosphere for different EUV fluxes with a Monte-Carlo model. We consider different possible sources of hot oxygen and carbon atoms in the thermosphere, e.g. dissociative recombination of O2+ , CO+ and CO2+ , photodissociation of O2 and CO, and other reactions like charge transfer. From the calculated production rate profiles we can get insights into the importance of the different source reactions. The resulting energy distribution functions at the exobase level are used to study the exospheric densities and the escape of hot oxygen and carbon. We discuss the escape rates of those atoms and the importance of different source processes compared to the present situation at Mars.
This work receives funding from the Austrian Science Fund (FWF): P 24247.