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Red Rover Goes to Mars
Well-Placed Opportunity
Opportunity drove up to exposed, layered bedrock in ¡§Eagle Crater¡¨ on Feb. 7, just two weeks after landing. It spent most of the next six weeks examining this outcrop, which arcs about halfway around the inner slope of the crater but stands only about as high as a street curb.
The rover discovered BB-size gray spheres embedded in the rock like blueberries in a muffin. These spherules are also plentiful in the soil of the area, apparently set loose when erosion wore away softer rock material around them. They contain hematite, the mineral whose detection from orbit had made Meridiani a compelling landing site.
Spectrometers on the rovers found that the outcrop is rich in sulfate-salt minerals, evidence that the rock had been drenched with salty water. The spherules are distributed throughout the rocks, rather than only in particular layers. This observation contributed to a conclusion that they are concretions, another sign of mineral-rich water soaking through the rocks. The microscopic imager revealed rippled bedding patterns in some of the finely layered rocks, indicating that the rocks not only were exposed to water after they formed, but actually formed from sediment particles laid down in flowing water.
Opportunity climbed out of Eagle Crater on March 22. It examined some rocks and soil on the dark surrounding plain, then headed east toward a sta-dium-size crater called ¡§Endurance.¡¨ It set a one-day martian driving record of 140.9 meters (462 feet) on April 17 and reached the rim of the crater on April
30.
The rover¡¦s panoramic camera and miniature thermal emission spectrometer surveyed the interior of ¡§Endurance¡¨ from two overlook points about a third of the way around the rim from each other. That information helped the rover team plot the safest route to the most interesting targets accessible. The rover drove into ¡§Endurance Crater¡¨ on June 8. It found that as far down as outcrops extended, they bore evidence of extensive exposure to water.
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