The Dynamics & Evolution of Martian Ices: Implications for Present-Day Liquid Water

The presence of ices (H2O and CO2) and liquid water is key to the evolution ofmartian geology, with implications for the potential for past or extant life, and the future of robotic and human exploration on Mars. In this dissertation, I present the first direct evidence that the smooth deposits covering mid-latitude, martian pole-facing slopes are composed of shallow dusty H2O ice covered by desiccated material. To analyze this H2O ice, I developed the first validated radiative transfer model for dusty martian snow and glacier ice. I found that these ice exposures have < 1% dust in them, and discovered the lowest latitude detection of H2O ice on Mars, at 32.9°S. After observing the ice disappear, and new gully channels form, I proposed a model for gully formation. In this model, dusty ice gets exposed by slumping, leading to melting in the subsurface and channels eroding within the ice and the wall rock beneath. Access to liquid water within this ice could provide potential abodes for any extant life. Next, I developed novel methodology to search for CO2 frosts within the entire Thermal Emission Imaging System (THEMIS) infrared dataset and found that about half of all gullies overlap with CO2 frost detections. I also used the Thermal Emission Spectrometer (TES) water vapor retrievals to assess the formation and distribution of H2O frosts on Mars. Additionally, I used radar data from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument to investigate Mars’ ice-rich South Polar Layered Deposits (SPLD). I discovered radar signals similar to those proposed to be caused by a subglacial lake throughout the martian SPLD. Finally, I mapped martian polygonal ridge networks thought to represent fossilized remnants of ancient groundwater near the Perseverance rover landing site with the help of citizen scientists across a fifth of Mars’ total surface area and analyzed their thermophysical properties. All these studies highlight the key role that ices and liquid water have played in shaping Mars’ landscape through time, and provide an intriguing path forward in martian exploration and the search for alien life.