Evidence for serpentinization in the Columbia Hills, Gusev Crater, Mars adds to their habitability

Mars Exploration Rover Spirit landed in Gusev crater on Mars in 2004. The crater was selected as the landing site because delta-like deposits at the mouth of a large inflow channel, Ma’adim Vallis, suggest that it once held a lake. However, Spirit landed on top of lava flows obscuring any potential lake sediments. The Columbia Hills are located near the center of the crater and are embayed by these lava flows, thus representing older material. Though not lake deposits, the hills reveal evidence for substantial aqueous alteration including fine-grained, layered outcrop containing the iron hydroxide goethite at the West Spur (Morris et al. 2006); the Comanche outcrop containing ~26% magnesium/iron carbonate (Morris et al. 2010); and opaline silica deposits (Squyres et al. 2008) indicating an ancient hot spring (Ruff and Farmer 2016) in the Inner Basin. The hot spring deposits resemble biosignatures found in hot springs on Earth (Ruff and Farmer 2016). Here we present evidence that the mineralogy at the West Spur as maeasured with Spirit’s Mössbauer (Morris et al. 2006) and miniature Thermal Emission Spectrometer (mini-TES; Ruff et al. 2006; Wang et al. 2006) is consistent with serpentinization. Furthermore, serpentinization at West Spur, carbonates at the Comanche outcrop and the opaline silica hotspring deposits in the Inner Basin can be linked via an evolving aqueous fluid. The process of serpentinization adds to the Columbia Hills’ habitability because it can result in the formation of organic molecules via Fischer-Tropsch synthesis, and release hydrogen, which could support microbial metabolisms.