Water gushes created "staircases" on Mars: study

http://news.yahoo.com/s/nm/20080220/sc_nm/mars_water_dc

Water gushes created "staircases" on Mars: study
By Will Dunham
Wed Feb 20, 2008

Sudden, tremendous gushes of water from underground most likely carved out unusual fan-shaped geological formations with steps like a staircase long ago on the surface of Mars, scientists said on Wednesday.

The Martian surface boasts perhaps 200 large basins that have formations resembling fans. About 10 of them are terraced, with what looks like steps into the basin. Since they were first seen three years ago, scientists have debated how these formations, some of them 9 miles wide, were created.

Dutch and U.S. researchers simulated on Earth on a vastly smaller scale the conditions that might have led to these formations on Mars that resemble dry river deltas with steps.

At a facility at Utrecht University in the Netherlands, they dug a crater in sand in a room-sized tub, then started water flowing into the crater. As the water flowed in through a channel, it eroded the sediment, then fanned out and deposited sediment as deltas, building steps down into the basin, very much like the Martian formations.

Erin Kraal, a researcher at Virginia Tech University who led the study published in the journal Nature, said these Martian formations probably formed quickly -- in a period of decades not hundreds, thousands or millions of years.

And they involved a lot of water.

"What you could imagine is something like the Mississippi River flowing for 10 years and then turning off, or the Rhine River flowing for 100 years and then turning off," Kraal said in a telephone interview.

"It's hard to image being able to get that much water to start so suddenly and stop so suddenly," Kraal added.

Kraal said the large volume of water needed to carve out these formations billions of years ago most likely burst from beneath the surface of the planet. "It doesn't look like it came from precipitation, or from rain. It looks like it came from a hydrothermal source or from melting ice," Kraal said.

Scientists want to understand the history of water on Mars because water is fundamental to the question of whether the planet has ever harbored microbial or some other life. Liquid water is a necessity for life as we know it. While Mars is now arid and dusty, there is evidence it once was much wetter.

For example, scientists think that long, undulating features seen on the northern plains of Mars may be remnants of shorelines of an ocean that covered a third of the planet's surface at least 2 billion years ago.

Currently, there are huge deposits of frozen water at the poles. And images taken by a NASA spacecraft suggest the presence of a small amount of liquid water on the surface. The images showed changes in the walls of two craters apparently caused by the downhill flow of water in the past few years.

(Editing by Cynthia Osterman)