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S.W. Squyres (Cornell University), Athena Science Team
The Mars Exploration Rovers ``Spirit" and ``Opportunity" have performed missions of scientific exploration at Gusev Crater and Meridiani Planum on Mars. Their objective is to search for evidence of water activity at the two sites, and to assess the past habitability of the sites.
The Gusev Crater site investigated by Spirit is a flat, rock-strewn plain. All rocks at the site investigated to date are olivine basalt. The rover has conducted a radial traverse through the ejecta blanket of the crater Bonneville. After investigation of this crater, the rover will continue its traverse toward the Columbia Hills, a range of hills over 100 m high approximately 2.5 km to the west. To date, no unambiguous evidence of aqueous activity has been found at the Gusev site.
The lander carrying Opportunity came to rest in a 20-meter crater in Meridiani Planum. Exposed within this crater is a small outcrop of bedrock. The bedrock outcrop has been studied in detail, and shows compelling evidence for formation and alteration processes involving liquid water. This evidence includes (a) embedded hematite-rich spherules that appear to be concretions, (b) tabular voids with characteristics consistent with those of molds of crystals formed by precipitation from water, (c) extremely high sulfur content, suggesting a compositon of 30-40 salts by weight, (d) significant quantities of jarosite, (e) Cl/Br systematics similar to those of terrestrial evaporites, and (f) cross stratification indicative of deposition in a moving fluid environment, probably water. Precipitated minerals at the Meridiani site could be very effective at preserving evidence of conditions and processes in the aqueous environment there, making them an attractive potential target for future study.
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.