美国宇航局：火星上存在液态水

Scientists at the U.S. space agency say that they have detected salty water streams appearing during summer on Mars. The finding supports the notion there may be life on the red planet.

Scientists have long known that there once was water on Mars. But they thought a change in climate had caused the planet to become arid. On Monday, NASA scientists announced they have evidence that there is more water on the red planet than previously thought.

Jim Green, NASA Director of Planetary Science, said, "Our rovers are finding that there is a lot more humidity in the air than we ever imagined. As we ingest the soils, they are moist, they're hydrated, full of water."

For several years scientists have monitored mysterious streaks on the slopes of Mars that appear to be waxing and waning. A comprehensive analysis of the data collected by NASA rovers reveals that the darker streaks showing up in the summer are most likely streams of water.

Michael Meyer, of NASA Mars Exploration, said, "But we don't know where the water actually comes from and so it could be hiding a major source of water in the subsurface. But we don't have any idea and so this is sort of the next puzzle to this recent discovery."

The answer to this and many other questions will be clearer in about five years, when the next big NASA rover brings back samples from Mars. The existence of water would indicate that there are living organisms on the planet.

It would also facilitate future space travel.

John Grunsfeld, NASA head of science, said, "When you have water ... you know, what's water? Hydrogen and Oxygen. That's what we make rocket fuel out of."

John Grunsfeld, NASA head of science, said, "From the Curiosity rover we now know that Mars once was a planet very much like earth, with warm salty seas, with fresh water lakes, probably snow kept peeks and clouds and a water cycle, just like we are studying here on earth with our earth science satellites, the water cycle here on earth. But something has happened to Mars and it lost its water, but we still have in the atmosphere and on the surface for the most part, but we still have the question, did life arise on Mars once and can we find out?"

The NASA announcement comes within days of the release of a new movie, The Martian, featuring Matt Damon as an astronaut stuck on Mars. Scott Ridley's science-fiction film, based on a best-selling book, is sure to increase curiosity about the planet.