These loose, BB-sized, hematite-rich spherules are embedded in this Martian rock like blueberries in a muffin and released over time by erosion. The Mars Rover Opportunity found this cluster of them at its Eagle Crater landing site and analyzed their composition with its spectrometers. Hypotheses about their formation have contributed to the story of water on Mars.
Image Number: WEB13448-2013
Credit: NASA/JPL-Caltech/Cornell University
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