 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
Patterns In Mars Craters Give Picture Of Drying Lakes
Potsdam, Germany (SPX) Sep 16, 2009 Networks of giant polygonal troughs etched across crater basins on Mars have been identified as desiccation cracks caused by evaporating lakes, providing further evidence of a warmer, wetter Martian past. The findings were presented at the European Planetary Science Congress by PhD student Mr. M. Ramy El Maarry of the Max Planck Institute for Solar System Research. The polygons are formed when long cracks in the surface of the Martian soil intersect. El Maarry investigated networks of cracks inside 266 impact basins across the surface of Mars and observed polygons reaching up to 250 meters in diameter. Polygonal troughs have been imaged by several recent missions but, until now, they have been attributed to thermal contractions in the Martian permafrost. El Maarry created an analytical model to determine the depth and spacing of cracks caused by stresses building up through cooling in the Martian soil. He found that polygons caused by thermal contraction could have a maximum diameter of only about 65 meters, much smaller than the troughs he was seeing in the craters. "I got excited when I saw that the crater floor polygons seemed to be too large to be caused by thermal processes. I also saw that they resembled the desiccation cracks that we see on Earth in dried up lakes. These are the same type of patterns you see when mud dries out in your back yard, but the stresses that build up when liquids evaporate can cause deep cracks and polygons on the scale I was seeing in the craters," said El Maarry. El Maarry identified the crater floor polygons using images taken by the MOC camera on Mars Global Surveyor and the HiRISE and Context cameras on Mars Reconnaissance Orbiter. The polygons in El Maarry's survey had an average diameter of between 70 and 140 kilometers, with the width of the actual cracks ranging between 1 and 10 meters. Evidence suggests that between 4.6 and 3.8 billion years ago, Mars was covered in significant amounts of water. Rain and river water would have collected inside impact crater basins, creating lakes that may have existed for several thousand years before drying out. However, El Maarry believes that, in the northern hemisphere, some of the crater floor polygons could have been formed much more recently. "When a meteorite impacts with the Martian surface, the heat can melt ice trapped beneath the Martian crust and create what we call a hydrothermal system. Liquid water can fill the crater to form a lake, covered in a thick layer of ice. Even under current climatic conditions, this may take many thousands of years to disappear, finally resulting in the desiccation patterns," said El Maarry. Share This Article With Planet Earth
Related Links EPSC 2009 Mars News and Information at MarsDaily.com Lunar Dreams and more
Ice Shouldn't Stop Dune Movement On Mars Or EarthTucson AZ (SPX) Jul 09, 2009 Planetary scientists have monitored some Martian sand dunes for more than 30 years, and the dunes have not moved during that time, leading scientists to question whether snow and ice trapped inside the dunes might be preventing movement. However a recent study published in "Geomorphology" shows that snow and ice are not enough in themselves to stop dune movement. While trapped ice and snow ... read more |
|
|
| The content herein, unless otherwise known to be public domain, are Copyright 1995-2009 - SpaceDaily. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal 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 SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement |
del.icio.us
Digg
Reddit
YahooMyWeb
Google
Facebook