Mars is currently very cold and dry, with conditions that do not support liquid water. However, earlier in the planet’s history, conditions may have been more amicable to liquid water- perhaps even enough so for an ocean to be present in the northern hemisphere until ~3.5 Gya. Laterally extensive paleoshorelines, originally interpreted via textural differences from orbital imagery of the martian surface, have been used as evidence for this ancient ocean. However, these interpretations remain contentious.
My thesis, titled “Numerical Modeling of Lake Bonneville Paleoshoreline Erosion at Mars-Like Rates and Durations,” investigated the plausibility of paleoshoreline features being preserved and identifiable today- after 3.5 billion years of slow martian erosion. Here on Earth, we have younger, uncontested paleoshorelines, which are determined via their topographic features- subtle breaks in hillslope with locally high slopes- rather than textural differences. These subtle topographic features are highlighted below in a transect containing Lake Bonneville (a Pleistocene paleolake from modern day Utah) paleoshorelines.
We ran several experiments and modeled linear hillslope diffusion on topographic data containing these three paleoshorelines at Mars-like rates and durations to investigate their survivability. Despite the slow erosion on Mars, given enough time (say, 3.5 billion years), we suspected that any identifiable trace would be eroded away.
The experiments produced outcomes of either paleoshoreline survival or erosion depending on the variables modified during each run. The figure below shows the results for two of the experiments after the modeled 3.5 billion years of erosion. The top transect shows a case in which the shoreline features were completely smoothed out and lost, and the bottom shows a case in which they persisted.
However, other, non-diffusive processes also erode Mars’ surface, and likely to a greater effect than diffusive hillslope processes. Because these other erosional forces (e.g. aeolian abrasion) are non-diffusive processes, they were not modelled here. So, we interpreted our results showing the unlikelihood of the subtle topographic features indicative of paleoshorelines still being preserved for us to observe on present-day Mars.
If you would like to read my thesis, you can find it here! This semester I plan on continuing this research to find statistical ways to analyze the initial and resultant topography, as these results were based primarily on visual interpretations.
-Zach