Dix Planetary Science Seminar

Abstract: Liquid water availability decreased with geological time on Mars. There is abundant geological evidence for large amounts of liquid water forming fluvial features and hydrated minerals early in Martian history. However, it is still unclear how much water was present at different periods in Mars' history and what subsequently happened to that water. We develop a model that simulates volcanic degassing, atmospheric escape, and crustal hydration and computes the global Martian D/H and water budget evolution through geological time. Simulation results are compatible with early Noachian water reservoirs of 100-1500 global equivalent layers (GEL), comparable to what has been proposed for pre-Noachian contributors to the Martian protoatmosphere. Our simulations show that the water availability decreases drastically during the Noachian. The Hesperian provides an interval where both a wet and dry Mars is possible. During the Amazonian, water availability was similar to today. The model results show that 30-96% of water was lost through crustal hydration. This highlights crustal hydration as the major water sink through Mars history and the role of irreversible crustal sinks in reducing habitability of terrestrial planets.

Abstract: In 2017, the Cassini spacecraft dove between Saturn's rings and the tops of its clouds. Flying only a few miles above Saturn's atmosphere, the spacecraft's orbital motion was affected by exquisitely fine details of Saturn's gravity field. Most of Saturn's gravity field was more or less what we expected, but traditional techniques failed to account for a significant component of the measured signal. In this work, we model how global seismic oscillations on Saturn warp its gravity field in time. We find good agreement with the data if Saturn tremors at unexpectedly high frequencies, singing a song we can only hear through its minute effect on gravity in the vacuum of space.