This image taken by the Mars Exploration Rover Opportunity shows a target dubbed "Grindstone" on a rock called "Manitoba" in "Endurance Crater." Opportunity dug a hole into the target with its rock abrasion tool, then captured this picture with its microscopic imager on sol 152 (June 28, 2004). The image mosaic is about 6 centimeters (2.4 inches) across.
Image Credit: NASA/JPL/Cornell/USGS
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