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Water on Mars - as recently as yesterday

martian gullies

Image taken by Mars Global Surveyor on 22.1.00 showing gullies (3 km wide) in the martian southern hemisphere which researchers think are due to an aquifer less than a few hundred meters beneath the surface. (Pic: NASA/JPL/Malin Space Science Systems)

While researchers have long suspected water existed in the past on Mars, new visual evidence suggests it might have flowed on the red planet as recently as yesterday.

Images to be published in the 30 June issue of the journal Science show new landforms, never before seen on Mars, which researchers think is evidence of a ground water supply, similar to an aquifer.

"We see features that look like gullies formed by flowing water and the deposits of soil and rocks transported by these flows. The features appear to be so young that they might be forming today," said prinicpal investigator, Dr Michael Malin.

The gullies are on otherwise geologically young surfaces which lack other landforms such as impact craters which would suggest an ancient landscape. The images taken by the high-resolution "eye" of the Mars Global Surveyor show steep-sided gullies, sinuous channels, and deltas of debris and suggest that liquid water may be lurking at shallow depths beneath the martian surface.

The presence of liquid water in the upper crust of Mars could be a boon for future human expeditions to the planet that could use the water for everything from basic survival to fuel cell energy and rocket propellant, the Science authors say. Some scientists believe that if life exists on Mars, it will be found in or near a water source.

Pic: NASA/JPL/Malin Space Science SystemsThe researchers calculate that seven community swimming pools worth of water was necessary to transport the amount of material seen in the debris fans. However the challenge has been to explain how any water on the martian surface could have survived evaporation under the sizzling martian temperatures, long enough to create the gullies.

Malin and colleague Kenneth S. Edgett suggest that the water exists in a porous layer of rock buried a few hundred meters below the martian surface, kept liquid by the pressure exerted by overlying rock. They propose that water seeps through the porous layer until it is exposed at the surface inside a crater or other depression. These first exposed trickles may freeze into a small ice "dam" at the surface. Meanwhile, groundwater continues to percolate through the rock and build up pressure behind this ice dam, creating a reservoir of fluid that eventually bursts through the dam and runs downslope, like the surge of flash flood waters.

If this is the correct scenario, the researchers suggest that the formation of the martian gullies may be linked to their location. Most of them occur in locations that get the least amount of sunlight in the martian day.

"There's still a finite chance that they were formed some other way," says Malin, "but there's a high probability they were formed by water."

The research team now plans to continue surveillance of the landforms to gather more evidence to support their water hypothesis and to see if they can catch the gullies in action.