by Staff Writers
Paris (AFP) March 16, 2014
Beneath its Sun-scorched exterior, the planet Mercury is cooling, which is causing it to shrink ever so slightly, scientists said Sunday.
Over the last 3.8 billion years, the planet has shrunk by up to 14 kilometers (8.8 miles) to reach its present diameter of 4,800 km (3,032 miles), they said.
Mercury, like Earth, is believed to have a superhot metallic core.
But unlike Earth, it has no tectonic plates which bump and jostle and slide in response to the stress that heat loss causes on the planet's crust.
Instead, Mercury has just a single, rigid top layer, which means the stress is transmitted directly to the planet's surface, causing it to "wrinkle" into gouges and ridges as the planet cools.
Planetary geologists led by Paul Byrne at the Carnegie Institution for Science in Washington used a tally of these features to get a yardstick for the planet's thermal contraction, the term for shrinkage through heat loss.
They studied nearly 6,000 landforms recorded by NASA's Messenger spacecraft to look for these telltales.
Earlier estimates based on images of only 45 percent of the planet suggested a contraction of 1.6 to six kilometres (one to four miles) over the course of its history.
The starting point for the measurement is the end of the "late heavy bombardment" of the Solar System -- a period that ran from around 4.1 billion to 3.8 billion years ago, when our star system was a shooting gallery of comets and other icy bodies which smashed into the nascent planets.
The study appears in the journal Nature Geoscience.
News Flash at Mercury
Mars News and Information at MarsDaily.com
Lunar Dreams and more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|