Water on Mars: NASA Scientists are "Excited"

Scientists say the rocks found by the Mars Curiosity rover look like they've been moved by water

Mars rover Curiosity found rocks on the Martian surface that are too big to be carried by wind, so researchers suppose water must have existed on Mars at one time. Over the next two years, Curiosity will continue its search for signs of ancient microbial life on Mars.

The NASA rover Curiosity has beamed back pictures of bedrock that suggest a fast-moving stream, possibly waist-deep, once flowed on Mars — a find that the mission's chief scientist called exciting.

There have been previous signs that water existed on the red planet long ago, but the images released Thursday showing pebbles rounded off, likely by water, offered the most convincing evidence so far of an ancient streambed.

There was "a vigorous flow on the surface of Mars," said chief scientist John Grotzinger of the California Institute of Technology. "We're really excited about this."

The discovery did not come as a complete surprise. NASA decided to plunk Curiosity down inside Gale Crater near the Martian equator because photos from space hinted that the spot possessed a watery past. The six-wheeled rover safely landed Aug. 5 after a nail-biting plunge through the Martian atmosphere. It's on a two-year, $2.5 billion mission to study whether the Martian environment could have been favorable for microbial life.

Present day Mars is a frozen desert with no hint of water on its radiation-scarred surface, but geological studies of rocks by previous missions suggest the planet was warmer and wetter once upon a time.

The latest evidence came from photos that Curiosity took revealing rounded pebbles and gravel — a sign that the rocks were transported long distances by water and smoothed out.

The size of the rocks — ranging from a sand grain to a golf ball — indicates that they could not have been carried by wind, said mission scientist Rebecca Williams of the Planetary Science Institute in Tucson, Ariz.

Though Curiosity did not use its high-tech instruments to drill into the rocks or analyze their chemical makeup, Grotzinger said scientists were sure that water played a role based on just studying the pictures.

It's unclear how long the water persisted on the surface, but it easily could have lasted "thousands to millions of years," said mission scientist Bill Dietrich of the University of California, Berkeley.

Curiosity chanced upon the dried-up streambed while driving to Glenelg, an intriguing spot where three types of terrain meet. Its ultimate destination is Mount Sharp, a mountain rising from the center of crater floor, but it was not expected to travel there until the end of the year.

Finding past water is a first step toward learning whether the environment could have supported microbes. Scientists generally agree that besides water and an energy source such as the sun, organic carbon is a necessary prerequisite for life.

While an ancient streambed holds promise as a potentially habitable environment, scientists don't think it's a good place to preserve the carbon building blocks of life. That's why the rover will continue its trek to the foothills of Mount Sharp where there's a better chance of finding organics.



By Alicia Chang, Associated Press

Slam-dunk’ Proof of Water on Mars

The Mars exploration rover Opportunity discovered a vein of the water-deposited mineral gypsum. "It's not uncommon on Earth," says Steve Squyres, "but on Mars it's the kind of thing that makes geologists jump out of their chairs." (Credit: NASA/JPL-Caltech/Cornell/ASU)

The vein, examined by NASA’s Mars exploration rover Opportunity, is about 16 to 20 inches long and the width of a human thumb, and protrudes slightly higher than the bedrock on either side of it. The vein and others like it are within an apron surrounding a segment of the rim of Endeavour Crater.

None like it were seen in the 20 miles (33 kilometers) of crater-pocked plains that Opportunity explored for 90 months before it reached Endeavour, nor in the higher ground of the rim.

“This tells a slam-dunk story that water flowed through underground fractures in the rock,” says Steve Squyres, professor of astronomy at Cornell University and principal scientific investigator for Opportunity.

“This stuff is a fairly pure chemical deposit that formed in place right where we see it. That can’t be said for other gypsum seen on Mars or for other water-related minerals Opportunity has found. It’s not uncommon on Earth, but on Mars, it’s the kind of thing that makes geologists jump out of their chairs.”

Last month, researchers used the microscopic imager and alpha particle X-ray spectrometer on the rover’s arm and multiple filters of the panoramic camera on the rover’s mast to examine the vein, which is informally named “Homestake.”

The spectrometer identified plentiful calcium and sulfur, in a ratio pointing to relatively pure calcium sulfate.

Calcium sulfate can exist in many forms, varying by how much water is bound into the mineral’s crystalline structure. The multifilter data from the camera suggest gypsum, a hydrated calcium sulfate. On Earth, gypsum is used for making drywall and plaster of Paris.

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