Find water to find life is NASA strategy

SIGNS OF LIFE: Second of a three-day series

Flagstaff astronomer Percival Lowell was wrong about the Mars canals - there are none - but his single-minded focus on the link between liquid water and life was on target.

``If Mars be capable of supporting life, there must be water upon hisIn the century that followed, biologists found organisms that get along just fine without sunlight or oxygen.

But they haven't found any creature that can live without liquid water.

If liquid water is a universal requirement of life, then the search for life beyond Earth becomes an exercise in celestial dowsing.

Instead of following a forked branch across the desert and waiting for it to dip, scientists use electronic gadgetry to sniff out the places in the universe that have, or once held, liquid water.

That's the strategy that guides NASA's long-term search for other habitable - and possibly inhabited - worlds: Look for water first, then look for life in those places.

In our own solar system, the search centers on Mars and Jupiter's moon Europa. And Arizonans are in the thick of it.

The surface of Mars is a cold desert today, but water-carved canyons and boulder-strewn flood plains suggest a planet that may once have been much wetter and warmer.

Arizona researchers are helping the space agency select landing sites for robots that will try to bring back fossil microbes trapped in water-formed minerals.

On Europa, Arizona scientists helped find compelling evidence for an ocean beneath the satellite's icy outer shell.

Scientists here have proposed new instruments that would resolve the ocean question.

If there is an ocean hidden beneath Europa's ice, the moon would become a target for robotic landers that would look for traces of life.

But if there's no liquid water, the focus of the life-search will shift to other worlds, possibly to other planetary systems beyond our own.

Photos by James S. Wood, The Arizona Daily Star: ASU geologist Jack Farmer, NASA researcher Jeffrey Moersch search out minerals on a Death Valley playa

Farmer gathers minerals he will examine for fossilized microorganisms.