Best Evidence Yet for Recent Water on Mars

Photographs returned by the Mars Global Surveyor spacecraft have revealed new bright deposits in Martian gullies that suggest water has flowed on the surface of the planet sometime in the last seven years. The images, taken in 2004 and 2005, show what appear to be deposits of minerals left by bursts of water running down the sides of two gullies, according to Michael Malin, the chief scientist for the spacecraft's camera system. The light-colored deposits were not there in pictures taken in 1999.

While previous evidence has shown water ice and water vapor exist below the surface of Mars, this is the "strongest evidence to date that water still flows occasionally on the surface of Mars," Malin said at a NASA press conference on Dec. 6. Cold temperatures on the planet, coupled with a thin atmosphere, do not allow water to persist on the surface of Mars. Researchers think water could remain liquid long enough, after breaking through from an underground source, to carry debris downhill before freezing or evaporating.

These new findings heighten the intrigue surrounding the potential for life on Mars; given water and a steady source of heat, bacteria can grow in extremely harsh environments. The shapes of the deposits are consistent with what one would expect to see if the materials were carried by water, NASA scientists said. The pictures show the liquid easily flowed around small obstacles on the way down a hill, eventually branching out like fingers at the end.

With the flow patterns traveling down the slope for 500 to 600 yards, project scientist Kenneth Edgett estimates the volume of each liquid burst was equivalent to "five to 10 swimming pools of water." The light tone of the deposits could be from frost being continuously replenished by ice from within the body of the deposit. Or the light color could be a salty crust, which would be a sign of water's effects on concentrating the salts. The deposits are unlikely to be caused by dry dust sliding down the slope because dust moved by rover tracks, dust devils and fresh craters on Mars is typically darker than surrounding areas.

More information on the Nasa Web site