LPL Colloquium: Dr. Shannon Curry
Observing Extreme Atmospheric Escape at Mars with MAVEN
Dr. Shannon Curry
University of California, Berkeley
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 2 years of observations of atmospheric loss at Mars over a variety of solar and solar wind conditions, including loss during extreme space weather events such as Interplanetary Coronal Mass Ejections (ICMEs) and Stream Interaction Regions (SIRs). We will report the current atmospheric escape rates and place them in context both with previous measurements of atmospheric loss by other spacecraft (e.g. Phobos 2 and Mars Express). We will also discuss the measured variability in escape rates for different drivers (e.g. solar EUV, solar wind pressure, etc.) and the implications for which processes drive the net atmospheric escape from Mars over time. Finally, we will address the implications for atmospheric escape at exoplanets, and the dominant escape mechanisms that may drive atmospheric erosion in other stellar systems.