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Thursday, February 28, 2002 Life on Europa? (CNN) - A planetary scientist says a combination of physical conditions on one of the moons of Jupiter might not only make life possible but also encourage it to evolve. Europa, an icy world that appears to be pocked with strange streaks of color, is continuously contorted by the powerful pull of its parent planet, the largest in our solar system. Richard Greenberg of the University of Arizona says those tidal forces could warm a subsurface ocean and push liquid pockets to the surface on occasion, helping nudge any primitive life forms to evolve. "The implication is that these settings would actually be hospitable to life," says Greenberg, who works on the NASA imaging team for the Galileo probe. It has orbited Jupiter since 1997. Galileo's photos and scientific measurements have provided strong evidence that Europa possesses the largest known salty ocean in our solar system underneath its frozen exterior. Besides water, ideal conditions for known life would include heat. And the gravitational tides put into motion by Jupiter might do the trick. Tidal forces periodically stretch the icy surface as high as 500 meters (more than 1,600 feet) above normal sea level. "Everything on and under the surface is driven by the tides," Greenberg says in a statement. In theory, the friction from this tidal pull could generate enough heat to melt the ice on the surface. And close-up photos of the surface indicate that exterior cracks frequently thaw and refreeze. "The ocean is interacting with the surface. There is a possible biosphere that extends from way below the surface to just above the crust," Greenberg said. @ 19:18 EST