Sequestration of Volatiles in the Martian Crust Through Hydrated Minerals: A Significant Planetary Reservoir of Water

Abstract Hydrated minerals as a reservoir of volatiles in the Martian crust have been widely acknowledged, but the size of this reservoir has not been estimated. Evidence for hydrated minerals has been shown in Martian meteorites, landed science measurements (Phoenix, Mars exploration rovers Spirit and Opportunity, and Curiosity), and orbital data (Mars Odyssey, Mars Express, Mars Global Surveyor, Mars Reconnaissance Orbiter). Global syntheses of the distribution of hydrated minerals shows that they are most common in Noachian-age crustal rocks and the common hydrated mineral phases detected are phyllosilicates, sulfates, opaline silica, and zeolites. The minerals are distributed in the top 10 km of crust where the abundance of these minerals ranges from not detected to >50%, but averages ≈0.5%–3.0%. Inverting hydrated mineral abundance to water volume integrated over the top 1 to 10 km of crust results in estimates of total volumes of this water reservoir of ≈15 m global equivalent layer (GEL) of water to ≈1000 m GEL.