NASA Spirit heads for Home Plate and slides into a volcano

William Atkins
Sunday, 06 May 2007 03:16

Science - Space

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The discovery adds to already known evidence of volcanic action on the planet. One prime example of volcanoes on Mars is the Olympus Mons, which is the tallest known volcano and mountain known to exist in the solar system.

Home Plate is a NASA nickname for a geological feature that looks like a baseball home plate. The rover Spirit has been exploring Home Plate since April 2006. It is a formation of layered bedrock (specifically, “clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements” [Science/Squyres]) about the size of a large house, but with a flat-topped shape, like a plateau, and with a pentagonal (five-sided) shape. It is located just south of Husband Hill within the giant Gusev Crater.

Three findings by Spirit visit to Home Plate lend credibility to the theory that Mars once possessed water. First, the area near Home Plate is composed primarily of basaltic rock. Such a find indicates that water may have mixed with magma beneath the Martian surface and, upon contact, caused an explosion—blowing out the basaltic rock. Second, the basaltic rock contains chlorine ions, which indicate that the rock might have contacted brine (saltwater).

Third, the lower slopes of Home Plate show evidence of “bomb sag”—which is a depressed bed that forms when soft deposits are deformed by the downward impact of rocks thrown outward by a volcanic explosion.

These important findings by Steve W. Squyres, of the Department of Astronomy at Cornell University (Ithaca, New York), and his team of researchers are written up within the article “Pyroclastic Activity at Home Plate in Gusev Crater, Mars” in the May 4, 2007 issue of the journal Science, volume 316. number 5825, pages 738-742.