The Martian surface has abundant evidence for the presence of stable liquid surface water over long periods of time in its history - a situation that cannot be accommodated by the present thin atmosphere. One possible inference is that the Martian atmosphere was more substantial long ago, and atmospheric particles have since been removed. Escape of the atmosphere to space is one possibility, but the amount of escape that has occurred over time is highly uncertain.
I will present results from the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft mission to evaluate the importance of atmospheric escape for the climate history of Mars. MAVEN has orbited Mars since September 2014, and is currently in an extended mission. I will highlight results that teach us about the chain of events that lead to atmospheric escape - including the drivers of escape from the Sun and solar wind, the atmospheric particle reservoirs for escape, and the escape processes and rates - with a special focus on plasma-related processes. I’ll then describe how lessons from MAVEN can teach us about planetary atmospheric evolution everywhere.