UA, NASA scientists agree on possiblity of life on Europa

Richard Greenberg, professor of lunar and planetary sciences, said images taken by Galileo, a spacecraft orbiting Jupiter and its moons, earlier this year show a number of surface features that are hard to explain without assuming liquid water is beneath the ice surface.

"There are places where it appears the surface has melted, the ice floating apart, tipped a little bit, and then refroze," Greenberg said.

So it appears there has been liquid water fairly recently, he said.

"We've known for a long time from Europa's color that its surface was made of ice," Greenberg said.

Paul Geissler, senior research associate for the University of Arizona's lunar and planetary sciences laboratory, said both water and heat are necessary to sustain life.

"Europa may have beneath its surface a substantial layer of water and sources of heat," Geissler said.

Therefore, Europa has the potential for life, he explained.

Geissler said the images recorded by the Galileo spacecraft Feb. 20 show long, linear fractures that are thousands of kilometers long. The images were released by NASA's Jet Propulsion Laboratory Wednesday.

"The only way to determine (if life exists) is to go and look," Geissler said.

Galileo is a satellite that was built in the 1970s and launched in 1989. It is currently orbiting Europa, recording images and transmitting them back to scientists in a matter of minutes, said Gregory Hoppa, a planetary sciences graduate student at the UA.

If life forms are discovered on Europa, they may not draw energy from sunlight.

Greenberg said there are places on Earth where life forms do not receive energy from the sun. Volcanoes deep under the ocean provide the heat that simple organisms need to survive.

Geissler said the next step in the search for life is to continue taking images of all areas on Europa's surface.

Europa rotates at the same rate it orbits Jupiter, so one side of the moon is always facing the planet, Hoppa said.

Geissler said scientists will send another satellite to Europa within the next decade. During this mission, a potential landing site would be determined for future spacecrafts.

The next step would be to land on Europa's surface, a mission that would take close to another decade, to determine what is under the ice surface.

The third step would be to dig beneath the ice surface and take samples for analyses.

Geissler said scientists are still deciphering images taken by Galileo.

"We wouldn't say we have the definitive answer," he said, "but it's the best hypothesis."

Galileo is orbiting Jupiter and its moons, taking images with an ultraviolet spectrometer, a near infrared mapping spectrometer, a photopolarimeter radiometer, which measures temperatures, and a solid-state imager, Geissler said.

Geissler, who is working with the solid-state images sent back from Galileo, said the instrument works much like a video camera, except that it takes pictures in colors not visible to the human eye.

It sends back images in both visible and near infrared color bands that tell scientists something about the moon's composition.