Mercury's shrinkage underestimated

by Timothy Oleson
Monday, June 23, 2014

The view from MESSENGER's second flyby of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

Using the most comprehensive survey of Mercury’s surface to date, collected by the MESSENGER spacecraft, Paul Byrne of the Carnegie Institution of Washington in Washington, D.C., and colleagues identified 5,934 different fault-related ridges and scarps totaling more than 400,000 kilometers in length. The new data indicate that the diminutive planet has actually shed about 5 to 7 kilometers off its radius, an estimate that better agrees with values derived from modeling of Mercury’s thermal evolution.

The uniform style of contraction that characterizes Mercury — with its single, all-encompassing tectonic plate — was once proposed as an explanation for mountains and faults on Earth. But this idea was abandoned with the recognition that our planet’s topography is more heterogeneously dispersed along plate boundaries, and that it loses heat through the motion of many tectonic plates.

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