Using 3D imaging, NASA studied Mars's terrain over the planet's four seasons, and found that water appeared to be flowing down slopes during spring and summer, and that these streams disappear completely in winter. NASA discovered these possible water flows in the middle latitudes of the planet's southern hemisphere, and the water is believed to be briny (i.e. slightly salty).
NASA's data show that there are at least 1,000 long and separate flows of water off these slopes. It's also worth noting that in the northern hemisphere, scientists previously discovered evidence of frozen pools of water and geological changes, such as new slopes and gullies.
Of course, if what NASA has found is indeed water, it does raise a few questions. For instance, at its coldest, temperatures on Mars can get down to -125°F--well below the freezing point of water. However, NASA states that salt water is able to withstand colder temperatures than normal water, and Mars can get up to around 23°F in its summer season, so it might be possible for there to be liquid water on the planet's surface. NASA is not yet sure why some of the slopes appear to look so dark around the water, though.
The discovery was made by the University of Arizona's Lunar and Planetary Laboratory, using the HiRISE Mars camera.
Of course, NASA hasn't proven anything just yet, but if this is really evidence of flowing water, it could be another indicator that plant or microbial life is possible on Mars.
