Transient liquid water and water activity at Gale crater on Mars

F. Javier Martín-Torres, María-Paz Zorzano, Patricia Valentín-Serrano, Ari-Matti Harri, Maria Genzer, Osku Kemppinen, Edgard G. Rivera-Valentin, Insoo Jun, James Wray, Morten Bo Madsen, Walter Goetz, Alfred S. McEwen, Craig Hardgrove, Nilton Renno, Vincent F. Chevrier, Michael Mischna, Rafael Navarro-González, Jesús Martínez-Frías, Pamela Conrad, Tim McConnochieCharles Cockell, Gilles Berger, Ashwin R. Vasavada, Dawn Sumner, David Vaniman

Research output: Contribution to journalArticlepeer-review

279 Citations (Scopus)


Water is a requirement for life as we know it. Indirect evidence of transient liquid water has been observed from orbiter on equatorial Mars, in contrast with expectations from large-scale climate models. The presence of perchlorate salts, which have been detected at Gale crater on equatorial Mars by the Curiosity rover, lowers the freezing temperature of water. Moreover, perchlorates can form stable hydrated compounds and liquid solutions by absorbing atmospheric water vapour through deliquescence. Here we analyse relative humidity, air temperature and ground temperature data from the Curiosity rover at Gale crater and find that the observations support the formation of night- time transient liquid brines in the uppermost 5 cm of the subsurface that then evaporate after sunrise. We also find that changes in the hydration state of salts within the uppermost 15 cm of the subsurface, as measured by Curiosity, are consistent with an active exchange of water at the atmosphere-soil interface. However, the water activity and temperature are probably too low to support terrestrial organisms. Perchlorates are widespread on the surface of Mars and we expect that liquid brines are abundant beyond equatorial regions where atmospheric humidity is higher and temperatures are lower.

Original languageEnglish
Pages (from-to)357-361
Number of pages5
JournalNature Geoscience
Early online date13 Apr 2015
Publication statusPublished - May 2015

Bibliographical note

We are grateful to all of the scientists and engineers who spent many years working to make the MSL mission such a success. We also acknowledge the contribution of the COSPAR Special Region Panel, and J-F. Buenestado-Castro for his support in the documentation process. Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.


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