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This image, acquired by NASA's Mars Reconnaissance Orbiter on Sept. 16, 2013, shows Roddy Crater on Mars, home to several large alluvial fans, which formed as water moved sediment from the mountainous crater rim and deposited it onto the flatter crater floor. Alluvial fans are found on Earth, Mars, and even Saturn's moon, Titan. The fans built up over time during intense rain storms or from melting snow. Due to the strong winds on Mars, the river channels that once carried water and sediment on the fan surfaces are now standing as raised ridges and platforms. A thin blanket of ejecta (upper r…
