Clay minerals on the surface of Mars (pictured) could be signs of previous volcanic activity rather than an indication that the planet had a warm and wet climate in the past, as has been assumed.
Clays can form when igneous rock is altered by water present at the surface or underground. But Alain Meunier at the University of Poitiers in France and his colleagues suggest that the Martian clays could have precipitated directly out of a water-rich magma, which filled voids in the igneous rock as it cooled. When the researchers analysed rocks from terrestrial lavas from a French Polynesian atoll, they found similar spectral signatures to those of the Martian clays.
The authors' suggestion — soon to be investigated by the Mars rover Curiosity — is that the planet's early climate was volcanic, but not necessarily wet.
Nature Geosci. http://dx.doi.org/10.1038/ngeo1572 (2012)
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Volcanic signs in Martian clays. Nature 489, 339 (2012). https://doi.org/10.1038/489339c
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DOI: https://doi.org/10.1038/489339c
