Craters
Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than 10 km in diameter) they usually have a central peak. The peak is caused by a rebound of the crater floor following the impact. Sometimes craters will display layers. Craters can show us what lies deep under the surface.
In December 2011, Opportunity Rover discovered a vein of gypsum sticking out of the soil along the rim of Endeavour crater.. Tests confirmed that it contained calcium, sulfur, and water. The mineral gypsum is the best match for the data. It likely formed from mineral rich water moving through a crack in the rock. The vein, called "Homestake," is in Mars' Meridiani plain. It could have been produced in conditions more neutral than the harshly acidic conditions indicated by the other sulfate deposits; hence this environment may have been more hospitable for a large variety of living organisms. Homestake is in a zone where the sulfate-rich sedimentary bedrock of the plains meets older, volcanic bedrock exposed at the rim of Endeavour crater.
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Beer Crater eroded west wall, as seen by CTX.
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Alga Crater, as seen by HiRISE. Click on image to see the relationship between Alga Crater and the larger Chekalin Crater.
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Timbuktu Crater, located on the edge of Capri Chasma. Image taken with THEMIS.
Read more about this topic: Margaritifer Sinus Quadrangle
Famous quotes containing the word craters:
“Listen.
We must all stop dying in the little ways,
in the craters of hate,
in the potholes of indifference....”
—Anne Sexton (1928–1974)