Author ORCID Identifier

https://orcid.org/0000-0002-1248-0676

Date of Award

2023

Document Type

Thesis (Master's)

Department or Program

Earth Sciences

First Advisor

Marisa C. Palucis

Abstract

Whether an ancient ocean existed on Mars remains controversial. Modeling of Mars’ early climate indicates a dry and cold environment; meanwhile geologic evidence supports a wet and warm environment that potentially hosted a globally connected aquifer with a northern ocean. One geomorphic line of evidence in support of persistent standing water and a northern ocean are inferred deltaic deposits along and near the Mars dichotomy boundary. However, not all these deltaic deposits appear to have consistent delta front elevations, and many are within craters, calling into question whether these deposits formed within the same body of water or even at the same time.

Here, we examined inferred deltaic deposits along, and in craters near, the crustal dichotomy in the Xanthe Terra region of Mars and use their delta fronts as proxies for past paleo-lake levels. We focused on delineating and extracting elevation profiles from 18 candidate deltas, corresponding to 18 possible paleo-lakes, with delta front elevations ranging from -2,988 m to 1,386 m. These lakes would have ranged in surface area from 10 to 2,696 km2 and depths of 21 to 392 m, requiring substantial water inputs to maintain. Using these data in combination with a combined surface-groundwater model, we find that these lakes were likely maintained under a subarid climate, with substantial inputs from surface runoff, though groundwater inputs from a regional aquifer would have been necessary. Crater counts on the floor of these craters suggest these lakes likely formed in the Hesperian between ~3.2 and ~3.5 Ga. This is in contrast to previous work in the region that suggested these paleo-lake systems occurred asynchronously, from surface runoff only, throughout the Hesperian and Amazonian. This work extends previous findings near Gale Crater, where mapping and modeling showed that crater lake systems over a large area were connected via a common groundwater table and that this groundwater table could have fed into a northern ocean or sea.

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