Planetary scientists have puzzled for years over an apparent contradiction on Mars. Abundant evidence points to an early warm, wet climate on the red planet, but there's no sign of the widespread carbonate rocks, such as limestone, that should have formed in such a climate. Now, a detailed analysis in the Dec. 21 issue of Science by MIT's Maria T. Zuber and Itay Halevy and Daniel P. Schrag of Harvard University provides a possible answer to the mystery.
In addition to being warmed by a greenhouse effect caused by carbon dioxide in the atmosphere, as on Earth, the early Mars may have had the greenhouse gas sulfur dioxide in its atmosphere. That would have interfered with the formation of carbonates, explaining their absence today.
It would also explain the discovery by the twin Mars rovers, Spirit and Opportunity, of sulfur-rich minerals that apparently formed in bodies of water in that early Martian environment. And it may provide clues about the Earth's history as well.
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| ©unknown
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| Neither Man nor Limestone.
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