LASP Science Seminars

Though dry and inhospitable to life as we know it today, Mars once hosted substantial surface liquid water, and Venus may have as well. Over time, much of the water from both planets has effectively been lost to space via escape of H and 2H (D) atoms. Understanding this desiccation is key to understanding our nearest neighbors, and by extension, conditions for habitability. In this talk, I will present recent advancements in studying atmospheric escape from both planets, using photochemical modeling and data analysis from the MAVEN mission’s Imaging UltraViolet Spectrograph (IUVS) instrument. The first part of the talk will focus on our recent publication in Nature, which demonstrated that H loss from Venus is dominated by HCO+ dissociative recombination, doubling estimates of present-day H loss and carrying implications for putative past oceans on Venus. Second, I will show how a combination of IUVS observations of OH prompt emission and photochemical modeling have led to a detection of water vapor in the martian thermosphere (100-150 km). This is the highest abundance of water vapor ever observed in Mars’ thermosphere, and occurred during the perihelion season, when a large amount of H (and thus, water) is lost. Finally, I will discuss ongoing work to 1) leverage the IUVS H and D Lyman alpha dataset at Mars to provide an independent detection of the thermospheric water, and 2) update our Venus photochemical model to include new species, cloud processes, and the lower atmosphere, in preparation for upcoming Venus missions.