Dark streaks on the walls of Garni crater Images taken from the Mars Reconnaissance Orbiter, a space probe in orbit around Mars, show long, dark streaks on the steep walls of the Red Planet's valleys and craters in the summer months of the Martian year. Some stretch downhill for hundreds of metres before they dry up in the autumn, when temperatures drop. In places, the streaks combine to form fan-like patterns. Researchers say the streaks are clear evidence of liquid water running down canyon and crater walls. This discovery raises the chances of Mars being home to some form of life. “Mars is not the dry, arid planet that we thought of in the past,” said NASA’s Jim Green. “Liquid water has been found on Mars.” The water flows on Mars could indicate the most promising sites to find life on Mars. These would then be key possible landing sites for any future human missions to Mars, as vital water supplies for the astronauts could be collected from natural sources.
Dark streaks on the slopes of Hale crater
Gully channels on Mars
Scientists have long suspected Mars has had liquid water on its surface in the past. Pictures beamed back to Earth from the Viking space probes that landed on Mars in the 1970s showed what looked like dried-up beds of ancient rivers and lakes. There are many valleys and channels that look as if they were carved by running water. The presence of sediments (muds and silts deposited in water) makes this even more likely to have been the case. NASA has since found evidence of an ocean that might have once covered much of the planet’s northern hemisphere millions of years ago.
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