Analysis of the Paleoenvironment of Gale Crater on Mars: Using Ephemeral Lakes in Western Australia as Analogs to the Mineral Assemblages of Gale Crater

Abstract:

Aluminum and Fe/Mg-phyllosilicates, as well as sulfates, are abundant in the layered sediments of the central mound of Gale Crater on Mars. Each of these mineral types are useful indicators of depositional conditions regarding pH, where Fe/Mg-phyllosilicates form in higher pH waters, while Al-phyllosilicates and sulfates form in more acidic waters. A general succession from higher pH aquatic environments to lower pH environments is evident during the Noachian and early Hesperian (3.6~3.8 Ga). However, substantial interbedding of these mineral groups is also observed at Gale, indicating pH boundaries that existed contemporaneously at the time of deposition. This is consistent with mineral distributions that are observed in ephemeral lakes on Earth, making them useful as analogs to the geochemistry of Gale Crater. This study will analyze the surficial mineral depositional patterns at Lake Gilmore, WA, to better understand how pH gradients are represented in contemporaneous sediment deposits. This will be performed by identifying minerals based on their unique reflectance signatures in the visible to near-infrared range (0.5-2.5 mm). Reflectance data collected by the HyMap™ hyperspectral scanner will be analyzed using the ENVI software to map the predominant minerals present on the lakebed surface. We expect to see minerals associated with a pH gradient that is related to lake depth, with Fe and alkali earth phyllosilicates representing deeper, less acidic waters, and aluminous phyllosilicates and sulfates representing near surface waters that are more acidic. This is potentially due to the circulation of upwelling groundwaters, or the change in chemistry may have arisen due to microbial activity, an intriguing possibility that would have significant implications for evidence of past microbial life on the Martian surface and would provide a more detailed picture of the paleoenvironment at Gale Crater.