Artist's concept of Mars Reconnaissance Orbiter
This artist's concept shows NASA's Mars Reconnaissance Orbiter mission over the red planet.
Minerals formed by water altering precursor geological materials are widespread on Mars. Most come from a wet era more than 3.7 billion years ago, early in the planet's 4.5-billion-year history. A new study shows that later alteration by water, within the last 2 billion years or so, may be more common than previously thought.

Geologists Ralph Milliken and Vivian Sun of Brown University, Providence, Rhode Island, surveyed sites near the center of 633 Martian craters, including 265 with deposits of clays and other hydrated minerals detected in observations from orbit.

At several of the sites, evidence pointed to local formation of the hydrated minerals inside relatively young craters. The study is reported in the Journal of Geophysical Research: Planets.

The full story from Brown University is at:

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Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown / Laurie Cantillo
NASA Headquarters, Washington
202-358-1726 / 202-358-1077 /

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