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It’s official: Mars had water, scientists say

The findings are published in a series of 11 articles this week in a special issue of the research journal Science.

A team of more than 100 scientists from numerous government agencies and universities co-wrote the articles. The research focused on findings from Opportunity, a Mars rover which for 10 months has roamed a region of Mars called Meridiani Planum.

One of the mission’s primary was to learn if liquid water ever existed on the red planet. That question has now been answered, said Mark Lemmon of Texas A&M University,  the principal author on one article and co-author on three others.

“The conclusion of the entire team, backed by substantial evidence, is that water was indeed present on Mars,” Lemmon says.

“The proof is there in several ways. There are sulfates [types of salt] present on Mars that were left behind when the water evaporated, plus other salts that show the definite presence of water long ago.

“Also, Opportunity examined rocks that show evidence of ‘cross-bedding,’ meaning ripples of water once flowed over them. There are also mineral deposits we call ‘blueberries,’ and on Earth we know these formations only appear if water is present.

“So the answer, without a doubt, is yes, liquid water was once on Mars. So far, we have not seen any evidence that liquid water is currently on Mars.”

The presence of water could mean that life - in some form - existed on Mars.

Lemmon says the atmosphere of Mars contains water, but in miniscule amounts.

“Even though we are currently seeing frequent clouds with Opportunity, if you squeezed all of the water out of the atmosphere, it would only be less than 100 microns deep, about the thickness of a human hair,” he said.

Because of the lack of water, weather on Mars is strongly affected by dust in the atmosphere. A small dust storm spread small amounts of dust around the planet one month before Opportunity and another rover landed.

“Both rovers saw very dusty skies at first. It was only after the dust settled after a few months that Spirit [the other rover] could see the rim of the crater it was in, Gusev Crater, about 40 miles away,” Lemmon said.

British scientists have speculated that the British Mars Lander, Beagle 2, crashed because the atmosphere was thinner than usual as a result of heating caused by atmospheric dust from the December storm.

“The other key question is when the liquid water was last present on Mars. Was it a few thousand years ago or billions of years ago?” he points out.

“We know that Mars is about four billion years old. We assume that water was there at any time from one to four billion years ago,” but don't know when water was last present.

Lemmon says the rock samples and mineral deposits tend to point to a large area of water that once existed on Mars, such as a lake or even a sea. “The marks on some of the rocks and other evidence suggest standing water,” he says.

“But whether this was once an ocean or other large body of water, we just don’t know.”

The next phase in the $820 million NASA mission will have Opportunity travel to another crater. Because the rovers use solar power and sunlight is currently limited on Mars, the rovers can only cover from 50 to 100 feet on a good day.

Spirit will continue climbing to the top of Husband Hill, informally named after the Columbia commander Rick Husband, which is the tallest hill in the area. The rovers are funded by NASA to collect data and send back photos through March, Lemmon says, but no one knows how long they will keep working. The rovers were originally designed only to operate through April 2004.

Lemmon is participating in another Mars mission in 2007 called Phoenix. This will go to Mars’ north polar region and dig into the permafrost -- a permanent layer of frost on the surface -- to search for evidence that Mars was habitable when this layer was liquid.

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