NASA's long-lived Mars rover Opportunity that beat newcomer sister probe Curiosity to an area containing water-formed clay minerals, has rolled into a region that may be far richer than scientists first realized.
A new study looks at chemicals spotted by a Mars-orbiting spacecraft to conclude that Endeavour Crater, which Opportunity reached in August 2011 after a 1,000-plus day, 13-mile trek across the plains of Meridian, is flush with a variety of clays, which on Earth, form in the presence of water.
Opportunity and an identical rover, Spirit, which is no longer working, landed on opposite sides of Mars in January 2004 to look for signs of past water.
Both found clear evidence that water has played a role in Mars' history, but the chemistry of the liquid was determined to be highly acidic, similar to battery acid, and not very friendly to life as we know it.
Clay minerals point to a different story, one involving a neutral water chemistry - water you could drink, lead rover scientist Steve Squyres, with Cornell University, told reporters at the American Geophysical Union conference in San Francisco this month.
If Opportunity's longevity continues - the rover was only designed to last 90 days - scientists may be in for a treat. A survey conducted with Mars Reconnaissance Orbiter's Compact Reconnaissance Imaging Spectrometer for Mars, or CRISM, instrument shows the rim and interior of Endeavour Crater contain a more diverse collection of two types of clay minerals than has been previously reported.
"If Opportunity can find a sample and give us a closer look, we should be able to determine how the rock was formed, such as in a deep lake, shallow pond or volcanic system," planetary scientist James Wray, an assistant professor at the Georgia Institute of Technology, said in a statement.
A more detailed understanding of Martian clays is expected to come from Curiosity, which landed Aug. 6 inside a giant crater that has a three-mile-high mound of layered deposits rising from its floor.
Unlike Opportunity, Curiosity is equipped with a sophisticated onboard chemistry laboratory to analyze rock and soil samples. Two of Opportunity's key science instruments also are no longer working.
The study is published in Geophysical Research Letters.
Image: A view from Opportunity's front hazard-avoidance camera (Hazcam) shows the rover's arm extended for examination of a target called "Onaping" at the base of an outcrop called "Copper Cliff"
in the Matijevic Hill area of the west rim of Endeavour Crater. The picture was taken on Dec. 16. Credit: NASA/JPL-Caltech