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Salt and Water Migration in Mars Duricrust Desiccation Experiments
  • Jamie Leigh Miller,
  • Charles Hibbitts,
  • Michael Mellon
Jamie Leigh Miller
Johns Hopkins University

Corresponding Author:[email protected]

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Charles Hibbitts
APL
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Michael Mellon
Cornell University
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Abstract

We have measured the salt content changes of soil samples in laboratory experiments to simulate the salt and water migration that may cause duricrust formation on Mars. Although the cold, dry surface of modern Mars lacks abundant, liquid water, salts may stabilize scant liquid water as thin films through freezing point depression, allowing them to migrate along temperature and water concentration gradients driven by evaporation at the surface, and to transport salts where they precipitate and cement loose soil grains into crusts. Our work also demonstrates that spectral data complements salt content changes we measured, by showing changes in the hydration states inferred in the 1950 nm water band. We simulated salt and water migration, required in salt crust formation, in Mars analog regolith, through desiccating wet loess doped with either MgCl2, MgSO4, or CaSO4 at a temperature range of -196 °C to 150 °C. Our experiments allowed exploring temperature and depth dependencies on water and salt behaviors in 2 cm tall cylindrical soil sample tubes. The 1000 nm to 2400 nm spectral slope and the area of the 1950 nm water band correlate with salt concentration. MgSO4 exhibits the greatest migration, CaSO4 hydrates with weak migration, and MgCl2 migrates with moderate hydration. Spectral analysis may be useful in estimating salt and water migration, and in turn, aiding in interpreting hydrological and climatic history of the regolith of Mars.