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Europe's Mars Express sees signs of a 'frozen sea' EUROPEAN SPACE AGENCY NEWS RELEASE Posted: February 23, 2005 The discovery of what could be a frozen sea close to the Martian equator, protected from disappearing by a thin layer of volcanic ash, was reported this week at the first Mars Express Science Conference in Noordwijk, the Netherlands.
Ice is unstable at the surface of Mars because of the low atmospheric pressure, and sublimates away (changes straight from ice to vapour without passing through the liquid state) into the atmosphere, but some of the ice rafts appear to have been protected by layers of volcanic dust. While the entire sea froze solid, the unprotected ice between the rafts sublimated to leave 'ice plateaus' surrounded by bare rock. The sparse cratering of this region shows that it cannot have formed more than about five million years ago, meaning this is a relatively young feature. The question remains as to whether the frozen body of water is still there, or whether the visible floes are just the remains of the sublimation process. Two observations suggest that the ice is still there: first, the submerged craters are too shallow, indicating most of the ice is still in the craters; and second, the surface is too horizontal if the ice had been lost, there would be a greater height variation. These findings were presented on 21 February at ESA's Mars Express Science Conference at ESTEC in Noordwijk, the Netherlands, where about 250 scientists from all over the world are discussing the first year of scientific results from Mars Express. The complete scientific paper by Dr J. Murray et al. describing the frozen sea results will be published by the journal Nature in March 2005. |
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