Long-term drying of Mars by sequestration of ocean-scale volumes of water in the crust

Geological evidence shows that ancient Mars had large volumes of liquid water. Models of past hydrogen escape to space, calibrated with observations of the current escape rate, cannot explain the present-day deuterium-to-hydrogen isotope ratio (D/H). We simulated volcanic degassing, atmospheric escape, and crustal hydration on Mars, incorporating observational constraints from spacecraft, rovers, and meteorites. We found that ancient water volumes equivalent to a 100 to 1500 meter global layer are simultaneously compatible with the geological evidence, loss rate estimates, and D/H measurements. In our model, the volume of water participating in the hydrological cycle decreased by 40 to 95% over the Noachian period (similar to 3.7 billion to 4.1 billion years ago), reaching present-day values by similar to 3.0 billion years ago. Between 30 and 99% of martian water was sequestered through crustal hydration, demonstrating that irreversible chemical weathering can increase the aridity of terrestrial planets.

Automated summary

Geological evidence indicates that ancient Mars had significant volumes of liquid water, with water levels potentially equivalent to a global layer of 100 to 1500 meters. Crustal hydration sequestered 30 to 99% of martian water, demonstrating that irreversible chemical weathering can intensify the aridity of terrestrial planets.