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Science & Space

Water on Mars? Flood of data, trickle of answers

By Robert Roy Britt

NASA administrator Sean O'Keefe (in red) and Director of JPL Dr. Charles Elachi (pointing) view the first images arriving from Spirit on January 4.
NASA administrator Sean O'Keefe (in red) and Director of JPL Dr. Charles Elachi (pointing) view the first images arriving from Spirit on January 4.

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Space Exploration
National Aeronautics and Space Administration (NASA)

( -- Nobody on the Mars rover science teams expected quick answers. But now the reality of the task is clear. Pinning down whether there was ever standing or running water at the landing sites of the twin Mars rovers is going to take some time. And the eager public will just have to wait, mission scientists made clear yesterday.

But an answer -- one way or the other -- could well be forthcoming.

What had at first been a stream of intriguing science pictures and data from the two-rover mission has dwindled to a trickle the past week or so. Pictures of rocks begin to look like other pictures of rocks. Were those Spirit's tracks in the soil or Opportunity's?

While the data may seem less interesting now, the spigot is wide open and the scientists are no less intrigued.

More than 11,000 images and 9.1 gigabytes of information have been returned by the two rovers, Cornell University astronomer Jim Bell said at a NASA press conference Thursday.

On several fronts, Bell and his colleagues are using the rovers' many instruments to explore intriguing hints of water. But now with press conferences reduced from one a day to one per week, it's clear the gee-whiz factor has given way to painstaking scientific investigation.

Spheres remain a mystery

No more information was provided yesterday on spherical grains in the soil and rock of Mars that have puzzled geologists since early February.

The spherules, as they are called, might have formed in the presence of water, but they could also be the result of a volcanic eruption or meteor impact. This week a couple of spheres were sliced in half and photographed, but they've not been fully analyzed.

More detailed images of soil have revealed a wider variety of grain sizes than had previously been noted. Bell said on one small scene scientist have noted "a fascinating array" of shapes, colors and probably compositions. Some of the larger, angular grains, a few millimeters in size, show preliminary signs of carrying hematite. This mineral often -- but not always -- forms in the presence of water.

Opportunity's Meridiani Planum landing site was chosen because an orbiting spacecraft had seen strong signs of the hematite. Ground observations have confirmed there is some. Now scientists hope to learn which flavor of hematite they're dealing with.

In other work, Opportunity has off-and-on for several days been grinding into rocks that are layered and might have formed in the presence of water. Microscopic images and other observations are being gathered from the drill sites.

As with all the other possible hints of water, though, scientists aren't sure what process caused the layering. Water would do it, but wind and volcanism could also do the trick.

Ray Arvidson, deputy principal investigator from Washington University in St. Louis, said further investigation of the minerals and chemicals in the rocks are needed to put together a complete story. He hinted that the chapters were being written by the data that's flowing back daily.

"That story is right around the corner," he said.


Opportunity's twin, Spirit, is working the massive Gusev impact crater on the other side of Mars. It is currently investigating a rock field that was once kicked up by nearby, more modest meteor impact -- a crater within a crater. Spirit will spend the next couple of weeks trudging toward the smaller crater, called Bonneville, while examining interesting rocks and soil patches all the way.

Don't expect any grand conclusions until all that data has been analyzed. And, quite possibly, what will be learned might involve just rocks, not water.

Gusev itself might once have been full of water, like Crater Lake in Oregon. But so far, it has not revealed any solid evidence to support that conjecture.

Both rovers recently dug trenches that revealed clumpy material that might involve very small amounts of water vapor from the atmosphere combining with salt in the soil to form a sticky brine. A full analysis of the trench data -- gathered by multiple instruments -- is underway.

Most scientists are convinced Mars was once warmer and wetter. The questions nowadays involve where the water was, where it went, and whether it was around long enough to foster life.

The rovers were each designed to determine if their landing sites once held standing or running water, where life might have percolated. Arvidson was asked if he's confident the data would eventually show that to be the case. He stressed that "we're in the middle of our job" and there was no way to tell yet which way it would go, wet or dry.

"I wouldn't be surprised if we'll be able to say a lot about the role of water -- or not -- at these two sites," Arvidson said. "I'm pretty confident that we're getting the data we need to answer the questions."

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