Flood on Mars Carved Instant Grand Canyon, Researchers Say
 

By Paul Recer
Associated Press
posted: 01:20 pm ET
21 June 2002

WASHINGTON (AP) _ Water roaring out of an overfilled lake carved an instant Grand Canyon _ a valley more than mile (1.6 kilometers) deep _ on the surface of Mars some 3.5 billion years ago, according to a new analysis of pictures taken by spacecraft.

Researchers at the National Air and Space Museum said the flood of water originated from a huge lake _ large enough to flood both Texas and California _ that overflowed into a nearby impact crater.

When that crater filled up, said geologist Ross Irwin, the water eroded away a ridge-like barrier and was sent rampaging across a plain. Within a short time, a deep and wide gully called Ma'adim Vallis was carved from the Martian surface.

``Imagine more than five times the volume of water in the Great Lakes being released in a single flood and you'll have a sense of the scale of this event,'' said Irwin, the first author of a study appearing in the journal Science.

The force and volume of the water was enough to carve a valley 6,900 feet (2,070 meters) deep and 550 miles ( 885 kilometers) long within a matter of months, he said.

Irwin said the study presents more evidence that Mars, now a cold, dusty place with water existing only as buried ice, was once wetter and warmer. He said some researchers have estimated that up to 40 percent of the Martian surface could have been covered with water, although that estimate will take more research to confirm.

The water is thought to have come from precipitation _ rain or snow _ from a warm atmosphere. Mars now has only a very thin atmosphere.

Irwin said a detailed analysis of pictures from the Mars Global Surveyor show the planet once had a lake that covered more than 424,000 square miles (1.1 million square kilometers) and was more than 3,600 feet (1,080 meters) deep. This lake spilled into and filled up a nearby, 300-mile-wide (500-kilometer) impact crater.

A ridge on the edge of the crater gave way, suddenly releasing the flood that carved Ma'adim Vallis, said Irwin.

Unlike Arizona's Grand Canyon, which was carved over millions of years by the Colorado River, Ma'adim Vallis was made ``within a matter of months, certainly less than a year,'' said Irwin.

The Martian valley has a broad riverbed on its floor, miles (kilometers) in width, in contrast to the relatively narrow riverbed on the floor of the Grand Canyon.

If Mars was once so wet, where did all the water go?

Irwin said nobody knows for sure, but theories suggest that some of the water was chemically split into its constituent parts, hydrogen and oxygen. The hydrogen could then have escaped to space. The oxygen stayed on Mars, rusting iron minerals and giving the planet its reddish color. Based on recent studies, at least some of the water was frozen and remains on Mars as sort of a permafrost underlying the planet's polar regions.