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Is Gusev Crater the site of an ancient Martian lake?.
Pasadena - Jan 09, 2004 Scientists analyzing data from NASA's Spirit rover to determine water levels at the landing site may not have a final answer for several more weeks, but today they announced that they had uncovered one tantalizing clue. "We came [to Gusev] looking for carbonates," said Phil Christensen, payload instrument lead for Spirit's mini-thermal emission spectrometer (Mini-TES). "And we have found carbonates." They are present, however, in only trace amounts - 1 to 2 percent of the surface soil. Mini-TES works in much the same way as a night-vision camera. Unlike human eyes, it "sees" in infrared; it detects heat. Because different minerals radiate heat at slightly different temperatures, an infrared spectrometer like Mini-TES can be used to analyze the mineral content of Mars's rocks and soil. Mini-TES is a miniature version of TES, the thermal emission spectrometer on onboard Mars Global Surveyor (MGS). The TES science team, which Christensen heads, reported several months ago in the journal Science that they had detected trace amounts of carbonates over large areas of the Martian surface, including in Gusev Crater. This hard-won finding - the TES team had been trying unsuccessfully for several years to find carbonates on Mars - was confirmed by Mini-TES, which detected a similar carbonate signature in the surface material at Gusev. Mini-TES did not find evidence of carbonates when it looked at rocks separate from the soil, but because most of the rocks at the Spirit landing site are small and Mini-TES samples a relatively large area at a time, to date the Mini-TES team has been able to acquire data on only a handful of larger rocks. The carbonates detected, both from orbit and by Spirit, are magnesium carbonates, a group of substances that are typically white and powdery. You probably have some magnesium carbonate in your bathroom at home: it's often used in making toothpaste and cosmetics. Carbonates require water to form. But, as rover scientists explained today, Spirit could be seeing nothing more than a dusty coating of carbonates, which could have formed through an interaction between water vapor in the atmosphere and rocks on the surface. If this proved true, it would not provide any evidence of the role of water in Gusev's past.
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