— In a groundbreaking discovery, NASA astronomers announced today they have found strong evidence that water flows on the surface of Mars. The finding makes it much more likely that life may exist or could have existed on the planet.
“We see features that look like gullies formed by flowing water and the deposits of soil and rocks transported by these flows,” said Michael Malin, principal investigator for the Mars Orbiter Camera on the Mars Global Surveyer spacecraft at Malin Space Science Systems in San Diego.
Photographs taken by the orbiting Mars Global Surveyer reveal images of walls streaked by crevices and gullies. The features appear on a number of craters, polar pits and Martian valleys. The indentations are made up of a deep channel with a collapsed region at its upper end (an “alcove”) and an area of accumulated debris (an “apron”) at the other end.
Malin and co-author Ken Edgett conclude in their study, to be published next week in the journal Science, that the streaks must have been formed by seeping water.
What was most shocking was that the features hinting of water flow appear to have formed relatively recently.
“They could be a few million years old, but we cannot rule out that some of them are so recent as to have formed yesterday,” Malin said.
‘Kicking and Screaming’
The scientists said they reached that conclusion somewhat reluctantly. Previous studies had detected land features on Mars carved by water, but all of those were billions of years of old. The only kind of water that scientists had believed exists on Mars is ice — frozen beneath the soil or tied up in polar icecaps, or as extremely sparse clouds in the thin Martian atmosphere.
“I was dragged screaming and kicking to this conclusion,” Edgett said today during a NASA press conference. “These things are so young.” But after scientists compared the Martian images with those of formation on Earth associated with water flow, they acknowledged the similarities were too striking to ignore.
One of the main puzzling factors is the atmospheric pressure at the surface of Mars, which is about 100 times less than it is at sea level on Earth. Under those conditions, liquid water would immediately begin to boil when exposed at the Martian surface. Investigators believe that this boiling would be violent and explosive. So how can these gullies form? Malin explained that the process must involve repeated outbursts of water and debris, similar to flash floods on Earth.
“We’ve come up with a model to explain these features and why the water would flow down the gullies instead of just boiling off the surface. When water evaporates it cools the ground — that would cause the water behind the initial seepage site to freeze. This would result in pressure building up behind an ‘ice dam.’ Ultimately, the dam would break and send a flood down the gully,” said Edgett.
Need for Caution Stressed
Some believe there is a need to remain skeptical.
Mike Carr, a planetary geologist at the U.S. Geological Survey, stressed today that conclusions about the images are still preliminary and need significant review. He pointed out that almost everything scientists thought they knew about Mars appears to go against the findings. He added that the gullies and streaks may have been caused by volcanic seepages, rather than by liquid water.