Evidence of Seasonal Water on Mars
Dark streaks running down the walls of several craters on Mars may be evidence of water flowing across the surface of the red planet during the Martian spring and summer. The discovery of the streaks, in images taken by NASA’s Mars Reconnaissance Orbiter, was reported by scientists at the University of Arizona. Since the mid-1900′s, scientists have gathered a great deal of evidence suggesting that water flowed over the Martian surface in the distant past.
Channels on Mars (NASA)
The finger-like streaks, which ranged from 1.6 to 16 feet (0.5 to 4.8 meters) wide, were seen in seven craters in various parts of Mars. All were on steep slopes facing the equator. Observed over three Martian years, the streaks appeared in late spring, grew and shifted during the summer, and disappeared in the fall. Some of the streaks grew as much as 600 feet (183 meters) over two Earth months.
The Arizona scientists said that though the streaks may have been caused by frozen carbon dioxide or even rock slides, their best explanation is salty water. However, they noted that they would not be able to confirm that water created the streaks without actually testing samples of the soil in the craters.
The scientists said that the surface of Mars is so salty that any water flowing there would certainly also be salty. The salty nature of the water may help explain its existence on the surface. Salt lowers the freezing point of water, so it can remain a liquid at temperatures colder than 32 °F (0 °C). The scientists doubted that life could exist in such a salty liquid.
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