Flow-like features on Dunes in Richardson Crater, Mars. They form around the dark dune spots, in the debris of the hypothesized Martian Geysers. The dark material at the end of the flows moves at between 0.1 and 1.4 m/day in late spring / summer on Mars. Most models for it favour liquid water as a cause. Either interfacial layers, or else layers of water created through the solid state greenhouse effect.