MAVEN observations of atmospheric loss at Mars

Shannon Curry (1) , Janet Luhmann (1) , Bruce M. Jakosky (2) , David Brain (2) , Francis Leblanc (3) , Ronan Modolo (4) , Jasper S. Halekas (5) , Nicholas M. Schneider (2) , Justin Deighan (2) , James Mcfadden (1) , Jared R. Espley (6) , David L. Mitchell (1) , J. E. P. Connerney (6) , Yaxue Dong (2) , Chuanfei Dong , Yingjuan Ma (7) , Ofer Cohen , Markus Fränz , Mats Holmström (8) , Robin Ramstad , Takuya Hara (1) , Robert J. Lillis (1)

1 SSL - Space Sciences Laboratory [Berkeley]
2 LASP - Laboratory for Atmospheric and Space Physics [Boulder]
3 Département de physique et d'astronomie
4 HELIOS - LATMOS
5 Department of Physics and Astronomy [Iowa City]
6 GSFC - NASA Goddard Space Flight Center
7 IGPP - Institute of Geophysics and Planetary Physics [Los Angeles]
8 IRF - Swedish Institute of Space Physics [Kiruna]

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been making observations of the Martian upper atmosphere and its escape to space since November 2014. The subject of atmospheric loss at terrestrial planets is a subject of intense interest not only because of the implications for past and present water reservoirs, but also for its impacts on the habitability of a planet. Atmospheric escape may have been especially effective at Mars, relative to Earth or Venus, due to its smaller size as well as the lack of a global dynamo magnetic field. Not only is the atmosphere less gravitationally bound, but also the lack of global magnetic field allows the impinging solar wind to interact directly with the Martian atmosphere. When the upper atmosphere is exposed to the solar wind, planetary neutrals can be ionized and 'picked up' by the solar wind and swept away.Both neutral and ion escape have played significant roles the long term climate change of Mars, and the MAVEN mission was designed to directly measure both escaping planetary neutrals and ions with high energy, mass, and time resolution. We will present 1.5 years of observations of atmospheric loss at Mars over a variety of solar and solar wind conditions, including extreme space weather events. We will report the average ion escape rate and the spatial distribution of escaping ions as measured by MAVEN and place them in context both with previous measurements of ion loss by other spacecraft (e.g. Phobos 2 and Mars Express) and with estimates of neutral escape rates by MAVEN. We will then report on the measured variability in ion escape rates with different drivers (e.g. solar EUV, solar wind pressure, etc.) and the implications for the total ion escape from Mars over time. Additionally, we will also discuss the implications for atmospheric escape at exoplanets, particularly weakly magnetized planetary bodies orbiting M-dwarfs, and the dominant escape mechanisms that may drive atmospheric erosion in other stellar systems.

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]

Shannon Curry, Janet Luhmann, Bruce M. Jakosky, David Brain, Francis Leblanc, et al.. MAVEN observations of atmospheric loss at Mars. American Astronomical Society, AAS Meeting, Jun 2016, San Diego, United States. pp.#213.01. ⟨insu-01369671⟩