Deltas
Researchers have found a number of examples of deltas that formed in Martian lakes. Finding deltas is a major sign that Mars once had a lot of water. Deltas often require deep water over a long period of time to form. Also, the water level needs to be stable to keep sediment from washing away. Deltas have been found over a wide geographical range.
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Delta in Lunae Palus quadrangle, as seen by THEMIS.
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Delta that fills a crater, as seen by HiRISE.
Read more about this topic: Lunae Palus Quadrangle