The fate of water on Mars: Tracing water-rock interactions through isotopic modeling, satellites, and rovers

Abstract: There is abundant geological and mineralogical evidence for large volumes of liquid water early in Martian history (~3-4 Ga). On present-day Mars, smaller amounts of water are stored in ice deposits. Based on these observations, liquid water availability appears to have decreased over geological time on Mars. However, the processes dictating the loss of water remain unresolved. Previous studies suggested that the fractionation of atmospheric hydrogen isotopes can be explained by significant water loss on Mars due to atmospheric escape. We hypothesize instead that the sequestration of water into the crust through hydrated mineral formation during the first 1-2 billion years of Mars’ geological history should also be considered as a key component of Martian water loss. Hydrated minerals occur across the entire 3-4 Ga crust at km-scale depth and are thought to have formed in a plethora of different aqueous environments, as evidenced through satellite and rover spectroscopy. For example, I have studied examples of deep hydrated mineral formation exposed in ~4 Ga giant impact craters. Most recently, my efforts on the Perseverance rover mission have led to the discovery of ~3 Ga carbonate- and sulfate-forming liquids that altered igneous rocks. In this presentation, I summarize these datasets in order to model Martian water history through an integrated hydrogen isotopic model that simulates hydrated mineral formation, volcanic outgassing, and atmospheric escape of water. My model results show that sequestration of water in the crust played a large role in the long-term drying of Mars, simultaneously explaining the hydrogen isotopic budget and geological observations of large past water volumes. This has implications for understanding the climate and the habitability potential of Mars on a geological time scale. Currently, the Perseverance rover is making its way to the extended mission area with the goal of further studying the processes that led to deep hydrated mineral formation in the 4 Ga crust on Mars.

About this Series: The Department Lecture Series at EAPS at MIT is a series of weekly talks given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. For more information and Zoom password please contact Madelyn Musick: mmusick@mit.edu