Among the most hotly debated topics among planetary geologists is whether liquid water is flowing on Mars today. This image shows gully channels in a crater in the southern highlands of Mars. The gullies emerge from the rocky cliffs near the crater's rim (upper left), then create meandering and braided patterns typical of water-carved channels. North is approximately up and illumination is from the left. Click here
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NASA / JPL / Univ. of Arizona