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Report: Europa's conditions could nurture life

A subsurface ocean may provide water and heat

This photo of Europa was taken by NASA's Jupiter probe, Galileo.
This photo of Europa was taken by NASA's Jupiter probe, Galileo.  

By Richard Stenger

(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.

The Galileo findings "opened the door to speculation about life," Greenberg says -- echoing one of the key premises in Arthur C. Clarke's 1998 "3001: The Final Odyssey."

In fact, Greenberg is expanding on concepts discussed for years by Jovian observers. As early as 1996, reports were being issued of new data that indicated possible support for "a primitive life form" on Europa. (Read a article, "Life on ... Europa?" from August 1996 on the status of inquiry then.)

Not just water

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.

Such an environment would offer a balance between stability and variety, the kind of conditions that encourage life to flourish and adapt.

"Necessity drives change," Greenberg said.

The Arizona researcher speculates that organisms on Europa could mimic microbial life forms in oceans on Earth, perhaps using photosynthesis for nourishment.

Disagreement in the field

Not all space scientists are as enthusiastic.

Norman Pace, a biochemist who studies life in extreme environments, says the prospects of finding something alive on Europa are extremely slim.

A professor at the University of Colorado at Boulder, he reasons that the chances of finding life are much better outside than inside our solar system.

"The basic theme here is that if you look at what is required for life," Pace says, "it really is a narrow window. Our solar system outside Earth doesn't seem too promising to sustain life.

"But we don't know what kind of extreme conditions conducive to life may be found elsewhere in the universe."


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