Cabrol said this scenario that she imagines occurred on ancient Mars is happening right now to the lakes in and around Licancabur. About 15,000 years ago, the climate there was much wetter and all kinds of life forms lived in the lakes. Then about 11,000 years ago the climate shifted and the environment began to dry out. Now much of the life that lives in the lakes does so in the presence of high UV radiation.
The study of these organisms gives the researchers insight to the extreme limits of life. Knowing these limits, especially in an environment that is considered Mars-like, combined with the data collected by the Mars rovers may allow the researchers to infer whether life could have thrived on the red planet.
Mars Water Search
The rovers were sent to Mars to find out if there was indeed a lot of water on Mars. "This starts with the premise that water is critical for life," said Cabrol. "This is the only model we know that works on Earth, so it's logical to look for that on Mars too."
The suite of instruments on the rovers are designed to look for features in the Martian landscape, rocks, and soil such as channels, fine-scale layering common to lake sediments, rounded rocks, and certain minerals that indicate a liquid past, said McSween.
To get to the point of looking for water on Mars with the rovers, scientists relied on evidence supplied by the Mars Odyssey and Mars Global Surveyor orbiters. If Spirit and Opportunity find more compelling evidence for water, the next step would be sending another lander equipped to detect life.
"These rovers were intended to search for water, not life, and they don't really carry the instruments that would be needed for biology," said McSween.
With Spirit now safely on the ground and sending back images of its surroundings, Robert Bodnar, a geologist at Virginia Polytechnic Institute in Blacksburg who studies Martian meteorites for signs of water, said landing in Gusev may really have been an ace in the search for water.
"When I looked at those images, I said I could convince myselfif I didn't know it was Marsthat that's an old lake, or an inland sea shoreline there," he said. "It certainly looked like that."
Confirmation will come as the rovers hack around the Martian landscape, keeping a detailed scorecard for mission scientists to carefully analyze.
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