Lack of carbonates deals blow to Mars life hopes
(Aug. 26, 2003)
An analysis of measurements taken by the thermal emission spectrometer aboard Mars Global Surveyor points to a deficiency of water-related carbonate minerals on the surface of Mars. These are the substances, found for example in limestone, that would be expected in abundance if, as previously believed, Mars had once been a warm, wet place, partially covered by oceans. MGS has found no detectable carbonate signature in surface materials at scales ranging from three to 10 kilometers (two to six miles) during its six-year Mars mapping mission. Trace amounts of carbonate have been found in Martian dust – proving that the MGS instrument is sensitive enough to detect the chemical's presence – but not in the form of outcroppings as originally suspected. These trace amounts can be explained simply in terms of the atmosphere interacting directly with dust and don't call for a theory involving marine deposits. We may have to adjust our thinking about ancient Mars from a waterworld friendly to the development of life to a dry, frozen planet hostile to biology. Doubtless the four probes currently on their way to the Red Planet, including the twin NASA Mars Exploration Rovers, ESA's Mars Express (carrying the Beagle 2 lander), and Japan's Nozomi, will shed crucial new light on this question.
