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Evidence from the Mars Express High Resolution Stereo Camera for a frozen sea close to Mars' equator


It is thought that the Cerberus Fossae fissures on Mars were the source of both lava and water floods1,2,3,4 two to ten million years ago1,2,5. Evidence for the resulting lava plains has been identified in eastern Elysium1,2,4,6,7,8, but seas and lakes from these fissures and previous water flooding events were presumed to have evaporated and sublimed away9,10,11. Here we present High Resolution Stereo Camera images from the European Space Agency Mars Express spacecraft that indicate that such lakes may still exist. We infer that the evidence is consistent with a frozen body of water, with surface pack-ice, around 5° north latitude and 150° east longitude in southern Elysium. The frozen lake measures about 800 × 900 km in lateral extent and may be up to 45 metres deep—similar in size and depth to the North Sea. From crater counts, we determined its age to be 5 ± 2 million years old. If our interpretation is confirmed, this is a place that might preserve evidence of primitive life, if it has ever developed on Mars.

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Figure 1: Views of plate-like terrain on Mars, and pack-ice on Earth.
Figure 2: Pressure ridges on Mars, and those caused on Earth by pack-ice drift against obstacles.
Figure 3: Age dating by crater counting12,13 on the pack-ice surface using HRSC (triangles) and MOC imagery over a total area of 380 km2 (squares and diamonds), including those craters that protrude through the surface from the substratum (circles).
Figure 4: Evidence of ice surface lowering and draping of plate-like features over partly submerged impact craters.

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We thank M. Wählisch for assistance in the MOLA processing and S. Clifford and N. A. Cabrol for criticism that greatly improved the paper.

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Correspondence to John B. Murray.

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The authors declare that they have no competing financial interests.

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A list of all members of The HRSC Co-Investigator Team and their affiliations appears at the end of the paper

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Murray, J., Muller, JP., Neukum, G. et al. Evidence from the Mars Express High Resolution Stereo Camera for a frozen sea close to Mars' equator. Nature 434, 352–356 (2005).

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