ORCID

http://orcid.org/0000-0002-9620-2891

Date of Award

Spring 5-15-2021

Author's School

Graduate School of Arts and Sciences

Author's Department

Earth & Planetary Sciences

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

The geomorphic expression of terrain provides information such as the underlying lithologic properties and the dominant surface processes. By examining the surface morphology of two impact craters on Mars that have been explored by rovers, we can synergistically combine orbital and ground observations to obtain a deeper insight into the geologic history. In this dissertation, we analyze the landscape evolution of Endeavour and Gale craters, which have been explored by the Opportunity and Curiosity rovers, respectively. This is accomplished largely by analyzing the topography on a larger scale using images from Mars orbiters and their associated Digital Elevation Models, combined with a smaller scale analysis of the topography from images taken by the Mars rovers. Chapter 2 discusses the degradation and evolution of Endeavour crater. Orbital data from the Mars Express and Mars Reconnaissance Orbiters (MRO) in combination with ground observations from the Opportunity rover is used to compare the topography of the relatively young Bopolu crater, to the nearby, and similar in size, Endeavour crater. Landscape evolution modeling is then implemented to simulate the degradation of Endeavour, and indicates that the crater experienced significant weathering and fluvial degradation during the Noachian period. The crater was then largely buried by the Burns formation sandstone, with only some segments of the rim remaining unburied. Aeolian erosion then modified the topography, exhuming sediment from the crater interior and eroding the rim. Chapters 3 and 4 discuss the evolution of Gale crater, using observations from MRO, Mars Express, and the Curiosity rover. Chapter 3 characterizes debris deposits within chutes that are visible within multiple canyons on Mount Sharp, and concludes that they are late-stage landslide failures and debris flow deposits. Infinite slope modeling indicates that failure occurred by reduction in effective stresses due to increased pore water, which is interpreted to be caused by late-stage precipitation. Chapter 4 examines the geomorphic expression of the Glen Torridon region near the base of Mount Sharp, where the Curiosity rover has explored. Glen Torridon contains the upper members of the Murray formation, and is just below a thick section of sulfate-bearing strata. The Glen Torridon morphology consists of a series of benches of polygonally fractured bedrock and smooth terrain containing periodic bedrock ridges. Mineralogical data from MRO indicates that these two types of terrain have the same ferric smectite signatures. Wind erosion is hypothesized to be responsible for the different geomorphic expressions, with more erosion occurring in northern Glen Torridon. This may be due to the uppermost Murray formation experiencing more diagenetic alteration, therefore being more indurated than the underlying strata. By using a combination ground and orbital observations at Endeavour and Gale craters, we have a better understanding of landscape evolution in two equatorial regions of Mars. In both areas, water was heavily involved in the evolution of the topography. At Endeavour crater, the rim was degraded from surface runoff, while at Gale crater, groundwater saturation and possibly exfiltration caused debris flows in the central mound. Both regions were later subjected to large amounts of wind erosion. At Endeavour, wind excavated some of the rim materials, creating its subdued appearance. At Gale crater, wind preferentially eroded the less indurated materials, creating ridges of resistant debris flow deposits, and terrain dominated by repeating benches and periodic bedrock ridges in Glen Torridon.

Language

English (en)

Chair and Committee

Raymond E. Arvidson

Committee Members

Jeffrey G. Catalano, Bradley L. Jolliff, Claire Masteller, Joseph A. O' Sullivan,

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