This close-up look at a patch of martian soil is the sharpest image ever taken of another planet. The picture was captured by the microscopic imager located on the Spirit's robotic arm. Scientists liken the alien soil to clumpy cocoa powder. The upper left corner of the soil patch is illuminated by direct sunlight and thus appears brighter. The actual size of the patch is about 3 centimeters (1.2 inches) across. Credit: NASA/JPL/US Geological Survey
