Enhanced Loss of O2+ and O+ at Mars from Electron and Ion Heating
Tuesday, 15 December 2015
Poster Hall (Moscone South)
We report results from the MAVEN Langmuir Probe and Waves (LPW) instrument, the Neutral Gas and Ion Mass Spectrometer (NGIMS) instrument, and numerical solutions, which suggest that ion and electron heating via plasma processes may have had a significant role in atmospheric and water loss at Mars. LPW in-situ observations of the electron temperature (Te) at Mars indicate a dramatic rise in Te (from < 600 oK to ~3000 oK) with altitude in the critical exobase region ~200 km in altitude. This dramatic temperature increase implies a strong ambipolar electric field (~1 V), which should strongly draw ions from the exobase region to higher altitudes. A substantial source of electron heating is required for this process. Numerical simulations demonstrate that observations of dramatically enhances O2+ at higher altitudes is consistent with a strong ambipolar electric field and plasma heating. With this new understanding, we demonstrate that ion loss, particularly the loss of O+ and O2+, could have significantly contributed to the loss of Mars atmosphere. The refilling time scales for the dayside O+ and O2+ will also be discussed.