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Life on the Red Planet? The Surface of Mars Revisited

NASA scientists studying image data from the Mars Global Surveyor spacecraft report that there may be current sources of liquid water at or near the surface of the red planet.

Gullies or valleys formed by flowing water appear to be recent additions to the martian surface and may still be forming today. These new landforms have never been seen before on Mars.

Twenty eight years ago the Mariner 9 spacecraft (a predecessor to the Viking spacecraft) found evidence of channels and valleys to suggest that billions of years ago the planet had water flowing across its surface. Ever since that time NASA scientists have been interested to learn where the water went. The Global Surveyor pictures suggest that some of water went underground, and quite possibly is still there. The presence of liquid water has profound implications for the possibility of life (as we know it) on the martian surface not only in the past, but perhaps even today. If life ever did develop there, and if it survives to the present time, then these landforms would be great places to look.

Since the atmospheric pressure at the surface of Mars is about 100 times less than that on Earth, liquid water would immediately begin to boil. Then how did these gullies form ? NASA scientists believe that the process must have involved repeated outbursts of water and debris, similar to flash floods. When water evaporates it cools the ground below it. This would cause the water left behind to freeze. The result over time would lead the formation of an 'ice dam.' Ultimately, the dam would break and send a flood of liquified water across the surface. Nearly all the gullies observed occur between latitudes 30 and 70 degrees south usually on slopes that get the least amount of sunlight during each martian day. If these gullies were on Earth they would be at latitudes between Sydney, Australia and much of the Antarctic coast.

The location of the gullies on the martian planet may justify observations made by mass spectrometers on board the NASA Viking landers. Viking 1 landed on Mars on July 20, 1976 on the western slope of Chryse Planitia (the Plains of Gold) at a latitute of 22.3 degrees north. Viking 2 touched down September 3, 1976 at Utopia Planitia at a latitude of 48 degrees North. The landers' gas chromatography-mass spectrometers each found no sign of organic chemistry at either landing site, but they did provide a precise and definitive analysis of the composition of the Martian atmosphere and found previously undetected trace elements. The three biology experiments discovered unexpected enigmatic activity in the Martian soil, but provided no clear evidence for the presence of living microorganisms in soil near the landing sites. Did the landers study the wrong hemisphere ?

The bulk of the water supply on Mars is believed to be about 100 to 400 meters below the planet surface. If water is available in substantial volumes in certain areas of the planet, it would make it easier for human visitors to access and use it for drinking and for use in portable energy sources. NASA is in the process of evaluating two options for a 2003 mission to Mars to study the formations further.

The NASA findings appear in the June 30 issue of Science magazine.


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