Scientists say they might be on the verge of confirming that large amounts of water once flowed in a region of Mars that has looked curiously dry until now. Such a finding could be comparable to their discovery earlier this year of an ancient shallow sea on the other side of the red planet.
Seven months after the U.S. Spirit robot landed on Mars, it has come across a rock named Clovis that has offered compelling evidence the area could have soaked in water at some point in the past.
"So far we have intriguing clues that this rock Clovis has interacted with liquid water," says the mission's lead scientist (Cornell University geologist) Steven Squyres. "We still need to understand the nature of that interaction. Better, we'd like to understand was it hot water or was it cold water? Was it water in the vapor phase or was it really in the liquid phase."
The United States launched Spirit and its twin rover Opportunity to opposite sides of Mars to determine whether water ever flowed there because water could mean that life existed there in the form of small microbes. A future rover mission will actually search for evidence of such life.
Opportunity has turned up signs of a salt water sea, but until now, Spirit has found that only traces of water once seeped through the ground in tiny veins, despite landing in what scientists believe is a dried lake bed. They were hoping that seas were distributed more globally.
Now, more than three kilometers from that landing site, Spirit has driven nine meters up into a hill formation where Clovis and rocks with a similar look appear to have been altered by a natural process that could involve a much greater amount of water flow. According to U.S. space agency rover scientist Douglas Ming, the clues were significant amounts of sulfur, chlorine, and bromine compounds in the rock.
"Sulfur, chlorine, and bromine are very common emission gases, of course, from volcanoes, and these can mix with vapors, with water, and this water, if it was potentially passing through this, could have been mixed with these elements, passed through this material and have caused some alterations," says Mr. Ming.
The scientists say it is too early to confirm that water flow was the process that deposited these compounds in the Clovis rock, which is brown and rough. Luckily in the vicinity are smoother, gray rocks that appear unaltered by water or any other natural weathering process, so Steven Squyres says Spirit will compare them to Clovis.
"If you have altered and unaltered rock side by side, if you can examine both, you get an idea of what the rock looked like before the alteration took place and what it looked like afterwards," he explains. "By looking at the change, you can really get a handle on what the nature of the alteration was."
Mission engineers say the two rovers on Mars continue to operate well, although they are showing signs of wear now that they have endured two-and-a-half times longer than they were designed to run.