Scientists have long known that water was abundant on ancient Mars, but there has been no consensus on whether liquid water was common, or whether it was largely frozen in ice.

Was the temperature high enough to allow the water to flow? Did this happen over an extended period, or just occasionally? Was the surface a desert or frozen? Warm conditions make it much more likely that life would have developed independently on the surface of ancient Mars. Now a new comparison of patterns of mineral deposition on the red planet with similar depositions on Earth lends weight to the idea that early Mars had one or more long periods dominated by rainstorms and flowing water, with the water later freezing.

Presenting the findings today at the Goldschmidt Geochemistry Conference in Barcelona, Professor Briony Horgan (Purdue University) said, "We know there were periods when the surface of Mars was frozen; we know there were periods when water flowed freely. But we don't know exactly when these periods were, and how long they lasted. We have never sent unmanned missions to areas of Mars which can show us these earliest rocks, so we need to use Earth-bound science to understand the geochemistry of what may have happened there.

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