CHARACTERIZING THE EXTENT OF HYDROTHERMAL ACTIVITY IN GUSEV CRATER, MARS

The Columbia Hills region within Gusev crater, Mars was recently selected as one of three potential landing sites of the upcoming Mars-2020 rover mission. The Columbia Hills have previously been explored by the Mars Exploration Rover Spirit and contain volcanic rocks, carbonate-bearing outcrop, pyroclastic deposits, and soils interpreted as hydrothermal deposits. Together, these materials may be indicative of an ancient habitable environment. Along its traverse, Spirit exposed anomalously bright soils with its inoperative right-front wheel in the vicinity of Home Plate, a plateau of layered pyroclastic sediments. Only five of these bright soils have been previously spectrally characterized in the literature, although several more were exposed and imaged by Spirit’s Panoramic Camera (Pancam). Additionally, there has been no systematic investigation of the regional extent of similar soils and other hydrovolcanic features within Gusev crater.

To better understand the extent of past hydrothermal activity, we have analyzed the full suite of Pancam multispectral images of all bright soil exposures. Previously, the soils Arad, Paso Robles, Gertrude Weise, Tyrone and Ulysses were found to have spectra indicating potentially hydrothermal mineralogies, with opaline silica and Fe-, Mg- and Ca-sulfates. In our analysis of six additional bright soil exposures, we found evidence of similar mineralogies, in addition to new spectral endmembers that have yet to be fully modeled. We have also studied all available CTX and HiRISE images of Gusev crater to search for additional hydrovolcanic features (e.g., candidate vent structures and “Home Plate-like” features). Beyond the Columbia Hills, no further features have been identified that resemble “Home Plate” or other candidate vent structures. While we have found a diverse mineralogy indicating hydrothermal deposits within the Inner Basin of the Columbia Hills, we have not found evidence from orbital mapping that there was widespread hydrothermal activity within Gusev crater.