Table of Contents at IgMin Research

Published: September 14, 2026 (29d)

Mineral Hydration as a Source of Accessible Water on Mars to Enable Human Missions at Equatorial Sites

Donald Rapp^*

Water is a scarce commodity on Mars, yet large amounts of water are needed for crew life support, and in most human mission scenarios, even greater amounts of water are needed to produce propellants for departing Mars for the return trip to Earth. Evidence suggests that significant amounts of water occur as mineral hydration of magnesium or calcium sulfates in the accessible upper layer of Mars regolith at various scattered equatorial locations. Several sulfates occur on Mars with water content 20% to 50% of the sulfate mass. 
Several forms of hydrated sulfates are known to provide a significant share of observed water-equivalent hydrogen in the upper meter of Mars regolith. These include “Gypsum” (CaSO₄⋅2H₂O) containing 20.9% H2O by weight, and “Epsomite” (MgSO4·7H2O) (commonly known as “epsom salts”) containing 51% H2O by weight, as well as hexahydrite (MgSO4·6H2O) and starkeyite (MgSO4·4H2O). 
Scans using the neutron spectrometer from orbit show a remarkable correlation between the occurrence of S and H in the equatorial region, indicating that hydrated sulfates are a primary source of H2O there. Recent higher-resolution scans using the collimated neutron spectrometer show significant pockets of higher H2O content. This implies that even higher local concentrations of H2O almost surely exist within those areas, most likely as hydrated sulfates.
The power requirements to evolve H2O from a range of potential hydrated magnesium sulfates are moderate. We suggest that a human mission to Mars at equatorial latitudes based on hydrated sulfates as a source of water is a potential competitor to a mission at higher latitudes based on putative accessible ice.