Earthly link is sought to life on MarsPage 2 of 2 -- "The real zinger is that a whole part of the geology of the Earth turns out to be accessible to microbes in ways no one knew before," said Kenneth Nealson, a professor of geobiology at the University of Southern California. "It forces people to consider there is a deep subsurface life on other planets. . . . It enlarges the horizon; it changes the definition of the habitable zone."
Designing a Mars mission that can locate such exotic forms of life will not be easy. Though some scientists believe that liquid water, and therefore microbes, could exist between the planet's frozen crust and its hot core, it will probably be decades or longer before scientists are able to dig deeply enough to look for them. The current rovers can dig into the Martian surface no deeper than about 6 inches. Three years ago, NASA created a new program called Astrobiology Science and Technology for Exploration of Planets, which is now funding 21 projects to help figure out ways to find signs of life elsewhere in the universe by first studying extremophiles on Earth. A prototype robot inchworm is being developed that can drill far below a planet's surface, while another project looks at using fluorescence to detect whether a specimen has DNA. The next Martian mission is a probe scheduled to land on Mars's northern polar cap in 2008, and some scientists hope that microbes might be found frozen in the ice there, either preserved extinct life or some kind of tiny organism waiting, in suspended animation, for a probe to warm it up. Failing that, the best evidence will be to look for the chemical trails that signify life. "We've asked the scientific community for ways of indirectly seeing life-bearing capacity," Garvin said. "It's a step removed from seeing little wriggly things do their thing." Despite the strange microscopic lives scientists are discovering on Earth and the possibility they exist elsewhere in the universe, they are sticking to one rule in their methodical search for life: Keep to the water trail. In March, the Mars rover Opportunity found what NASA says is conclusive proof that there was once water on Mars, although it is unknown whether it occurred in vast oceans or mere pools or for how long it persisted. However, it represents the first clear sign that Mars may have had the foundation to support life. "Studying life in extreme environments reinforces our focus on water," says Rosalind A. Grymes, associate director of NASA's Astrobiology Institute. "One thing all these life forms need at some point in their life cycle for some limited time is liquid water. That is our highest payoff."
Beth Daley can be reached at bdaley@globe.com. © Copyright 2004 Globe Newspaper Company.
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