Editor's Summary

14 December 2006

Martian highs and lows

Mars is a planet of two halves: the northern hemisphere is dominated by sparsely cratered lowlands, and the south by heavily cratered highlands. Many explanations have been offered for this dichotomy: new data from the MARSIS radar sounder on-board Mars Express should now help to filter out some of these by establishing the age of the northern lowland crust. Radar images reveal signs of ten buried impact basins in an area of the northern lowlands, most of them hidden from view on the surface. Taking these features into account, crater densities in the north and south become broadly comparable. If the northern lowland crust is at least as old as the oldest exposed highland crust, as these results suggest, the differences between the two hemispheres must have originated early on in the geological evolution of Mars.

Letter: MARSIS radar sounder evidence of buried basins in the northern lowlands of Mars

Thomas R. Watters, Carl J. Leuschen, Jeffrey J. Plaut, Giovanni Picardi, Ali Safaeinili, Stephen M. Clifford, William M. Farrell, Anton B. Ivanov, Roger J. Phillips and Ellen R. Stofan

doi:10.1038/nature05356

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