One of the things that NASA is actively seeking out in our solar system is the presence of liquid water. The presence of liquid water is assumed to be a necessity for not only life on other planets, but for the possibility of manned mission to other planets in our solar system. NASA has announced that the Mars Reconnaissance Orbiter has found new evidence of liquid water flowing on the surface of Mars in the spring and summer seasons.
The orbiter shot photos of what NASA describes as "dark, finger like projections that appear and extend down some Martian slopes during late spring through early summer." NASA says that the best explanation of what these dark streaks are is flows of "briny water." The idea is that the presence of salt in the water lowers the freezing temperature and the sites with active flows get warm in the shallow subsurface.
The water is thought to be about as salty as the oceans here on earth. Pure water would freeze at the temperatures observed. The finger-like flows are thought to be about half a yard to five yards wide with lengths of up to hundreds of yards. The flows in the photo above are from the Newton crater and the photo you see is a combination of orbital imagery with 3D modeling to show what the flows would look like in the spring and summer on a slope inside the crater.