Insights into the Geologic History of Mars’ Northern Lowlands from Near-Infrared Spectroscopy

Author: Pan, Lu

Year: 2017

Degree: Dissertation (Ph.D.)

Advisor: Ehlmann, Bethany L.

Committee Members: Yung, Yuk L.; Rossman, George Robert; Grotzinger, John P.; Ehlmann, Bethany L.

Option: Planetary Sciences

DOI: 10.7907/Z94747WX

Abstract

Hydrated minerals, identified on Mars using near-infrared spectroscopy data, reveal new insights into the aqueous processes and evolution of climate in the history of Mars. Through investigations of the mineralogical record using near-infrared spectroscopy, this dissertation focuses on the geologic history and aqueous processes in the northern lowlands of Mars in order to assess the existence of a long-lived global ocean, the extent and volume of Noachian-Hesperian volcanic flows filling the northern lowlands, the nature of aqueous activity in the most recent Amazonian age, and the spectral variability of carbonates. The first chapter reports widespread and diverse mafic and hydrated mineralogy of units associated with impact craters across the northern lowlands. In the lowlands-wide survey, no pervasive carbonate or evaporative salts are found in support of a northern ocean, but we identify widespread phyllosilicates inferred to be Noachian basement materials excavated beneath 1-2 km of mafic lava flows. In the second and third chapters, combined analysis of imagery and spectral data is used to investigate local geologic processes related to liquid water in the knobby terrains of Acidalia and in the vicinity of Lyot crater. Phyllosilicates and hydrated silica are detected in the knobby terrains of Acidalia indicative of a declining prevalence of aqueous alteration through time. We also find diverse mineralogy in the vicinity of Lyot, probably formed in a hydrothermal system and later excavated by the Lyot impact. In contrast, we did not identify mineralization related to local channels that are syn- or post-impact. The fourth study analyzes the spectral properties of unshocked and impact-shocked carbonate rocks on Earth and found similar spectral characteristics between Mars carbonate detections and terrestrial carbonates in impact environments. Using near-infrared spectroscopy, we have identified and characterized the mineralogic record of Mars, and found past environments within the northern lowlands of Mars with varying style and intensity of aqueous alteration through time, with implications for the evolution of Mars climate.

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