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Meteorites show Mars has more water than expected

June 22, 2012|By Thomas H. Maugh II
  • An image of Mars shows white clouds in the atmosphere and ice at the poles.
An image of Mars shows white clouds in the atmosphere and ice at the poles. (NASA )

Water, water, everywhere. Earlier this week, astronomers found a pocket of water at the bottom of a crater at the moon's south pole. Now, another team has found unexpectedly large amounts of water in Martian rocks blasted to Earth by meteors striking that planet's surface.

A team from the Carnegie Institution of Washington reported in the journal Geology that they found the water in meteorites from two different locations on Mars' surface and that the amounts are similar to what might be found on Earth.

The findings shed new light on the geologic history of Mars and raise the possibility that the Red Planet might once have sustained life.

A team headed by Francis McCubbin, a former post-doctoral fellow at Carnegie who is now at the University of New Mexico, analyzed two shergottite meteorites. These are fairly young meteorites that originated by partial melting of the Martian mantle (the layer under the crust) and crystallized on the surface and in the shallow subsurface.

Meteorite impacts about 2.5 million years ago then launched them into space, where they eventually made their way to Earth. Their composition uniquely identifies them as Martian in origin.

The two meteorites had very different histories on Mars, said geochemist Erik Hauri of Carnegie. "One had undergone considerable mixing with other elements during its formation, while the other had not," he said. "We analyzed the water content of the mineral apatite and found that there was little difference between the two even though the chemistry of trace elements was different. The results suggest that water was incorporated during the formation of Mars and that the planet was able to store water in its interior during the planet's differentiation."

From their analysis, the team concluded that the mantle from which the meteorites was derived contained between 70 and 300 parts per million of water. The upper mantle of Earth, in comparison, contains 50 to 300 ppm of water.

The new findings, Hauri added, suggest that volcanoes may have been the primary vehicle for getting water to the Martian surface.

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