Finding only trace amounts of carbonate minerals on Mars isn't the only strike against the hypothesis that most of the Red Planet was once wet and warm (see "Martian Invasion," in this week's issue: Martian Invasion). The presence of large amounts of olivine, a mineral that undergoes rapid transformation into other minerals when exposed to liquid water, also argues against ancient oceans or lakes on Mars.
Using the same spectrometer on the Mars Global Surveyor spacecraft that found the carbonates, Todd M. Hoefen of the U.S. Geological Survey in Denver, Philip R. Christensen of Arizona State University in Tempe, and their colleagues found substantial amounts of olivine in a Martian region called Nili Fossae. The mineral is abundant in a 30,000-square-kilometer area within Nili Fossae, a complex of depressions and fractures adjacent to an impact basin, the researchers report in the Oct. 24 Science. The absence of water is more than skin deep. A spectrometer aboard the Mars Odyssey spacecraft detected olivine in a layer about 7 km below the rim of the canyon Valles Marineris, Christensen reported earlier this year. The olivine layer suggests the mineral at Valles Marineris "did not encounter subsurface water at any time in its long life, nor has it [encountered] surface water since it was exposed in the wall of the canyon," he notes.
If you have a comment on this article that you would like considered for publication in Science News, send it to email@example.com. Please include your name and location.
Philip R. Christensen
Department of Geological Sciences
Arizona State University
Tempe, AZ 85287-6305
Todd M. Hoefen
U.S. Geological Survey
Denver Federal Center
Denver, CO 80225
Cowen, R. 2003. Martian invasion. Science News 164(Nov. 8):298-300. Available at [Go to].