Wrinkled Mercury’s shrinking history Agencies Posted On Tuesday, March 18, 2014 at 10:30:01 AM London: The planet Mercury is about seven km smaller today than when its crust first solidified over four billion years ago. New evidence by NASAs messenger aircraft has confirmed that the planet has shrunk much more than was previously estimated. The new finding solves an apparent enigma about Mercurys evolution. Messenger which launched in 2004 and was inserted into orbit in 2011, continues collecting scientific data, completing its 2,900th orbit of Mercury later this month. Mercurys surface differs from Earths in that its outer shell, called the lithosphere, is made up of one tectonic plate instead of multiple plates. To help gauge how the planet may have shrunk, the researchers looked at tectonic features, called lobate scarps and wrinkle ridges, which result from interior cooling and surface compression. The features resemble long ribbons from above, ranging from 5 to more than 550 miles long. Lobate scarps are cliffs caused by thrust faults that have broken the surface and reach up to nearly 2 miles high. Wrinkle ridges are caused by faults that dont extend as deep and tend to have lower relief. The scientists mapped a total of 5,934 of the tectonic features. With Messenger, we have now obtained images of the entire planet at high resolution and, crucially, at different angles to the sun that show features Mariner 10 could not in the 1970s, said Steven A Hauck, II, a professor of planetary sciences at Case Western Reserve University and the papers co-author. With the new data, the researchers were able to see a greater number of these faults and estimate the shortening across broad sections of the surface and thus estimate the decrease in the planets radius. Paul K Byrne and Christian Klimczak at the Carnegie Institution of Washington have led a team that used Messengers detailed images and topographic data to build a comprehensive map of tectonic features. That map suggests Mercury shrunk substantially as it cooled, as rock and metal that comprise its interior are expected to. They estimate the planet has contracted between 4.6 and 7 kilometres in radius.
Posted on: Tue, 18 Mar 2014 05:08:46 +0000
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