February 19, 1998 in Nation/World

Proof Positive? Photos Indicate There Was Water On Mars, And Where There’s Water, There’s Life

Robert S. Boyd Knight-Ridder
 

The odds that Mars once supported life have been strengthened by a set of spectacular new pictures from a NASA spaceship circling our neighboring planet.

The latest images indicate that liquid water probably existed on Mars for at least a million years - long enough for primitive organisms to form - said Wesley Huntress, NASA’s associate administrator for space science.

Earlier evidence sent back by the Mars Pathfinder lander last year confirmed that an enormous flood took place on Mars a billion or more years ago, but did not reveal how long the water remained on the now bone-dry surface.

“This is the first evidence of long-term water flow, not just a catastrophic event,” Huntress told a meeting of the American Association for the Advancement of Science in Philadelphia.

In recent years, scientists have come to believe that life is possible - perhaps probable - wherever there is liquid water, even in conditions of extreme heat, cold or darkness.

Understanding how life might have gotten an early toehold on Mars, and why it apparently disappeared, could help explain the origin of life on Earth and the dangers of environmental change.

The new pictures were returned by the Mars Global Surveyor, a science satellite that began orbiting the Red Planet last September. It will spend the next two years taking detailed pictures of the entire Martian surface in preparation for future landings.

One Surveyor image shows what appears to be a dried river bed inside a mile-and-a-half wide canyon known as Nanedi Vallis, part of a series of valleys cutting through plains in the Xanthe Terra region near the Martian equator, about 1,000 miles southwest of the Pathfinder landing site.

The channel meanders back and forth over the canyon floor, bending, looping and following different paths, much like the Mississippi River.

“This is clear evidence of a fast-flowing river bed that changed its course several times,” Huntress said. “It probably took a million or so years to form.”

Another picture shows terraces along the base of mighty cliffs lining another valley, 600 miles farther south, known as Vallis Marineris. Huntress said they resemble the terraces formed by the Colorado River as it carved the Grand Canyon in Arizona.

Other images reveal what appear to be dried-up lake beds, like the landscape in the American Southwest, and a multiplicity of fine-grained sand dunes, further evidence of long-vanished water.

The Global Surveyor also sent back fresh pictures of the Martian south pole, where NASA’s Polar Lander will touch down in December 1999. They show bands of eroded, layered rock, reminiscent of the edges of Alaskan ice sheets.

The Polar Lander will spend three months searching for traces of subsurface water in the frozen terrain. Its package of scientific instruments includes two “microprobes” designed to dig three feet below the surface and report what they find.

Recent discoveries on Earth - under the ocean, at the bottom of oil wells, in boiling hot springs and acid pools - show that simple life forms can thrive in extreme environments.

“We used to think that life was fragile,” Huntress said “But wherever liquid water and chemical energy are found, there is life. There is no exception. Life may be a cosmic imperative.”

According to NASA officials, whether life once existed on Mars - or still does - probably cannot be answered until a spaceship returns samples of rocks and soil to Earth for detailed study. Such a mission is planned to depart Earth in 2005 and return in 2008.

Doubts are growing that the famed meteorite, ALH84001, picked up in the Antarctic actually contains fossils of Martian organisms, as reported in 1996. Some scientists say the fossils are really inorganic artifacts created during the meteorite’s fiery ride through space.

“It’s very difficult to come to a consensus,” said Klaus Kiel, a physicist at the Hawaiian Institute of Geophysics and Planetology. “A robotic return of samples is essential.”


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