Giant flood channels uncovered on Mars

Partially buried northwestern slope valleys (NSVs) could have raged with floodwater

By Richard Stenger
CNN

(CNN) -- The largest valley system in the solar system, discovered underneath layers of hardened lava, ash and dust on Mars, could have delivered enough water to fill an ocean within a matter of weeks, according to scientists.

Dwarfing anything on Earth, the flood channels were spotted by a satellite in Mars orbit that can peer with a laser instrument under the planet's surface.

The network of gorges, situated in the Western Hemisphere between a giant volcano and the possible remnants of an ocean, is 10 times larger than its nearest rival on the red planet, according to the researchers.

Cataclysmic floods that at times unleashed 50,000 times the flow of the Amazon River most likely formed the outflow system, which boasts individual channels as wide as 125 miles (200 km), the scientists said.

"After picking the complex geologic picture apart like a jigsaw puzzle, we think there must have been several episodes of (volcanic) heating creating catastrophic floods," said James Dohm of the University of Arizona in Tucson this week.

James Dohm mapping the geology of the red planet

Such discharges could have filled an ocean three times the size of the Mediterranean in less than two months, calculated the scientists from the University of Arizona, NASA and U.S. Geological Survey. A smaller sea nearby could have filled within eight days.

Scientists have speculated for some time that the desert planet teamed with water and periodic oceans billions of years ago. But the latest research lends weight to the theory that the planet experiences episodic changes that transform the surface in an instant, geologically speaking.

The presence of the northwestern valley slopes provides further evidence that Mars possesses vast underground stores of frozen water.

Occasional blasts of internal heat can melt the aquifers and release torrents of water, producing temporary oceans and seas, which sink back underground and return the planet to desert conditions, according to Dohm and colleagues.

Such volcanism could happen again and form an ocean or lake over the northern plains, the Arizona scientists theorize.

The team, which published their most recent findings in the June issue of the Journal of Geophysical Research, combined observations from the Mars Global Surveyor, currently in Mars orbit, and the Viking spacecraft, which circled the red planet in the 1970s.