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Chemical Analysis of Six Martian Meteorites Indicates That Water was Once Abundant On Mars



The Field Museum in Chicago
February 22, 2001

Field Museum Scientist Discovers Signs of Water on Mars - Chemical Analysis of Six Martian Meteorites Indicates That Water was Once Abundant on Mars

A chemical analysis of Martian meteorites supports the controversial theory of water on Mars, according to Meenakshi Wadhwa, PhD, associate curator of meteoritics at The Field Museum in Chicago. Her research is scheduled to be published in the February 23rd issue of Science.

Last year, an analysis of images of Mars taken by NASA's Mars Global Surveyor spacecraft revealed surprising evidence that the planet was once a watery place. On Earth, sedimentary rock is formed by deposition from water, and the photographs of Mars show hundreds of layers of sedimentation.

It has generally been assumed that Mars is more oxidized than Earth, partly because of its red surface, which is caused by the presence of iron oxides. But the new evidence indicates that only the outermost rind (i.e., crust) of Mars is moderately to heavily oxidized.

This leads to the question of just how did the crust of Mars become oxidized? ``On Earth, the most common oxidizing agent is water, so my research supports the idea that abundant water was present in the crust of Mars at one time,'' Dr. Wadhwa says. Whether water was ever present on Mars is especially intriguing because water is thought to be a necessary ingredient of life.

The fact that the crust of Mars is much more oxidized than its deep interior reveals another new piece of information about the mysterious red planet. It means that the oxidized crust of Mars has not mixed extensively with the planet's mantle, a layer between the planet's crust and its interior core. ``Therefore, Earth-style plate tectonics is not likely to be taking place on Mars,'' Dr. Wadhwa says.

In contrast, the Earth's mantle (especially the upper part nearest to the crust) is oxidized by ``crustal recycling,'' the mixing of the planet's water-oxidized crust with mantle rocks due to plate tectonics.

Although NASA has plans to gather rocks from Mars, rare SNC (Shergottite - Nakhlite - Chassigny) meteorites are the only Martian rock samples scientists currently have to study. Dr. Wadhwa determined the oxidation condition of six of the meteorites by analyzing minute amounts of a rare earth element (specifically, europium) in a mineral known as pyroxene, which makes up a major portion of these rocks. The meteorites are thought to have been produced by volcanic processes on Mars 180-474 million years ago.

The Field Museum houses one of the best collections of meteorites in a museum setting. Founded in 1893, it is one of the world's great museums and research centers. It is home to more than 70 scientists in geology, anthropology, botany, culture, environmental studies, and zoology.

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