Ancient Climate & Hydrology on Mars and Earth

Abstract

This dissertation presents five mostly independent projects. Most broadly, they are unified by the desire to understand the ancient climates of Earth and Mars. They are also variations on the themes of computational modeling, hydrology, land surface geometry, and habitability. In the first chapter, I look into the hydroclimate of Gale Crater on Mars. I find that in an intermittently warm climate, relatively short-lived lakes must have been filled by surface water with an active atmospheric hydrological cycle, not groundwater. The second chapter addresses the consequences of early martian ocean hypotheses for Jezero Crater, another location of significant interest. Recent ocean hypotheses imply that Jezero was submerged by the ocean, but the geological history of Jezero contradicts this possibility. Chapter 3 reviews an elegant model of the first stage of the Messinian Salinity Crisis, then explains why this model is critically flawed. The fourth chapter returns to martian shorelines with an analysis of the extent to which craters whould have obliterated such features, concluding that the earliest proposed features would have been largely destroyed. This drives another nail into the Arabia Level's coffin. Finally, Chapter 5 is a novel analysis of how continental configuration affects climate. Using an ensemble of 120 randomly generated continental configurations, a global climate model is used to estimate global weathering rates and understand the effects of continent size and latitude. Surprisingly, continent latitude is relatively unimportant and although size matters, about half of the weathering variability is unexplained by either. The complex interaction between continental geometry and atmospheric dynamics introduces considerable variability and could help explain the irregular nature of Earth's climate record on the longest time scales.