Sensitivity of elastic thickness to water in the Martian lithosphere

Ancient Mars likely hosted oceans similar to those on Earth; however, such water is not presently observed on Mars. One possible explanation for the lack of present-day oceans is that surface water was transported into and stored within the interior of Mars throughout the geological history. As water can influence the rheological structure of the Martian lithosphere, we investigated the sensitivity of the elastic thickness of the lithosphere to water using recent laboratory data. Calculations indicate that the presence of water results in a significant decrease in elastic thickness relative to dry conditions at a given thermal structure. Gravity and topographic data acquired by the Mars Global Surveyor and other orbiters indicate a temporal change in elastic thickness during the geological history of Mars. The extremely thin elastic layer during the planet’s early history can be explained by a water-rich rheological model, whereas a dry rheology can account for the relatively thick elastic layer inferred during the later evolution of Mars. Although thermal evolution of Mars has a large uncertainty, the strong sensitivity of elastic lithospheric thickness to water suggests possible sequestered water into deeper levels during the early history of Mars.