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Did Martian Oceans Bubble From Below?

2008-02-22 20:00:03 | Weblog

Did Martian Oceans Bubble From Below?


Gusev Crater
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Gusev Crater
This image taken in 2005 by the Spirit Rover shows the sunset casting a blue glow above the rim of Gusev Crater on Mars. Fan-shaped deltas at the edge of huge basins scattered across Mars were probably formed by a titanic influx of water, gushing from the bowels of the Red Planet, according to study released.



Fan-shaped deltas at the edge of huge basins scattered across Mars were probably formed by a titanic influx of water, gushing from the bowels of the Red Planet, according to study released Wednesday.

The origin and morphology of the deltas, studded with curious step-like terraces, have perplexed scientists since they were first observed three years ago.

Today the surface of Mars is bone dry, but a growing body of evidence suggests as much as a third of its surface was at one time covered with oceans.

But scientists have differed -- sometimes sharply -- as to exactly where the water came from.

A quartet of researchers at Utrecht University in the Netherlands led by Erin Kraal, using satellite images and topographical data from the Mars Orbiter, hypothesized that these unique formations could only have originated from a single, massive basin-filling event.

Their study, published in Nature, also concluded that the water rushed in over a period measured in tens of years, not millions, as many scientists had thought.

And not just a little bit, either.

"Water volumes would be that of the Mississippi River over the course of 10 years, or the Rhine River flowing for 100 years into a 62-mile-wide basin," said Krall.

Rainfall could not have accounted for so much water over such a short timespan, which means that it must have come from deep within the planet.

Krall's findings bolster research, published last year, suggesting that Mars once had a criss-cross underground water system that may have latticed the entire planet.

Still unexplained, however, were the strange fan-shaped geological formations studded with steps leading into the basin. Were they consistent with the theory of a massive flow of liquid from the planet's interior?

To find out, the researchers refined an experiment that they had first conducted as part of a high school science class.

"There are no fans with steps on Earth, so we had to build one," said Kraal, who is now a geoscience researcher at Virginia Tech University.

The scientists dug a mock crater in a roomful of sand, then simulated water flow into the crater.

As the fan, created by the incoming stream of water, intersected with the rising water level in the basin, steps -- much like the ones observed on Mars -- appeared.

"As the water flows in through a channel, it erodes the sediment," explained Kraal. "The water fans out and deposits the transported sediment as deltas, building steps down into the basin."

Kraal points out that there were likely other sources of water on Mars, and that his theory only explains the dozen or so large basins -- averaging 60 miles across -- with fans seen on satellite images and data collected by a laser altimeter aboard the U.S. orbiter.

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