The above image was taken back in May by the Mars Reconnaissance Orbiter, a satellite orbiting Mars that takes photos of the Martian surface. First released last Friday, the image depicts dark brown streaks on the edge of a crater. These streaks appear during the Martian summer, then fade away during the winter months, and reappear again the next summer. It's believed that these streaks are actually flowing liquid salt water on Mars! That's right, I said flowing liquid water! Over the past decade or so, astronomers have found much evidence that water flowed on Mars sometime in the past, but they believed that conditions on Mars today are too harsh to support liquid water. I guess they were wrong!
The main thing preventing liquid water from flowing on other planets is temperature. Planets closer to the sun than Earth are too hot; any water would evaporate. Planets farther away from the sun than earth are too cold; any water would freeze. Temperatures on Mars range from 68 F during the summer, to -124 F in the winter, with an average of -81F. So in the summer months Mars can get warm enough to have flowing liquid water! One thing that also helps is the fact that the Martian surface is very salty. This salt gets dissolved in any surface water, lowering the freezing point of water and preventing it from turning to ice. (This is why we throw salt on the roads in the winter, it lowers the waters freezing point preventing ice from forming.) Any water on Mars will be very salty, allowing it to be in liquid form at fairly cold temperatures. Water that has dissolved as much salt as it can possibly handle has a freezing point of -4 F.
This discovery of this water on Mars has once again peaked interest in astronomers minds about searching for life on Mars. Maybe there are some microbes or bacteria that live in the water during the summer months? We will have to wait for the next round of Mars rovers to find out!
Image Credit:HiRISE, MRO, LPL (U. Arizona), NASA
Image Credit:HiRISE, MRO, LPL (U. Arizona), NASA
