This is an image of a Martian river valley.
Click on image for full size
Image from: NASA
Martian River Valleys
Unlike the Martian outflow channels, these Martian river valleys have many tributaries.
These river valleys do not resemble their terrestrial counterparts either, however. The tributaries are very short, about 100m long (the length of a football field), as if the running water ran out quickly.
One explanation for these is that they formed from melting ground ice. The ground ice could have melted either from a period of global warming, a period of local warming due either to volcanic activity, or from water circulating underground. (Evidence of underground circulation of water has implications for life on Mars.)
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