Water-limited hydrothermalism and volcanic resurfacing of Eridania Basin, Mars

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Hughes, Emmy B.
Wray, James J.
Karunatillake, Suniti
Fanson, Grace
Harrington, Elise
Hood, Don
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The Eridania Basin system, located in the martian southern highlands, is considered a promising site of long-lived lacustrine hydrothermalism. Despite its multi-basin scale and suggested longevity that should pervasively alter the regolith, anticipated compositional signatures have been unexplored at regional scales. Here we synthesize orbital datasets (derived from the Gamma Ray Spectrometer, GRS; Thermal Emission Spectrometer, TES; and Compact Reconnaissance Imaging Spectrometer for Mars, CRISM) to characterize the composition of Eridania’s landscape progressively from regional to outcrop scales. The bulk geochemistry representing decimeter depths and mineralogy of the Eridania region lack substantial evidence for a long-lived lacustrine body. Instead, regional chemical trends are consistent with minor alteration and a generally mafic composition, particularly in the southern Eridania region. This suggests either limited regional hydrothermalism or extensive mafic resurfacing occurred in Eridania—the latter of which is consistent with previous studies. Meanwhile, chloride mapping and analyses of amorphous silica and acid-altered clay phases at outcrop scale both show that mineralogical evidence for hydrothermal alteration and putative lacustrine activity is limited to the northernmost basin, and that most other amorphous silica in Eridania is consistent with low-to-minimal water/rock weathering. Our findings collectively suggest that Eridania underwent localized crustal hydrothermal alteration, perhaps akin to sinter and fumarole units on Earth, with any paleolakes either regionally confined or extensively resurfaced to at least meter scale depths by later volcanism. This supports prior inferences of spatially and temporally limited fluvial processes on Mars and extensive volcanic resurfacing of basins, as in Gusev Crater.
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Creative Commons Attribution 4.0 International (CC BY 4.0)