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Report: Jupiter's moons possess food for life

Scientists say hidden oceans on Europa and other Jovian satellites could provide the energy that life needs
Scientists say hidden oceans on Europa and other Jovian satellites could provide the energy that life needs  


By Richard Stenger
CNN

(CNN) -- While shrouded in ice and darkness, oceans underneath the crusty exteriors of several Jovian moons could possess the raw materials necessary to feed hordes of creatures, according to a new study.

The planet-size moons likely have one prerequisite to known life already: Observations from NASA's Galileo probe give strong indications that sister satellites Callisto, Ganymede and particularly Europa have subsurface oceans with more saltwater than Earth.

But could those watery depths support life? Yes, according to two California space researchers in the June 15 issue of the journal Science.

"Our paper suggests that it is possible, and this is only a possibility, that high enough oxygen levels could build up in the oceans so that larger forms of life could be supported," Christopher Chyba, a scientist with SETI (Search for Intelligent Life Institute), told CNN. "I would still view this as much less likely than microbial life."

Such life forms might could draw energy from numerous chemical processes in the oceans, sidestepping the need for sunlight or photosynthesis, which most terrestrial life relies on, at least indirectly.

"Most life on Earth depends on photosynthesis. The first link in the food chain is chlorophyll's conversion of sunlight into chemically stored energy," said Chyba in a statement.

"Imagine an ocean on Europa, a huge, bottled-up body of water capped with miles of ice. Photosynthesis isn't going to work there. Nonetheless, there are other ways to make a metabolic living in those dark seas."

Life forms on Earth, to stoke their cellular metabolic furnaces, tap into the energy released from the chemical union of two substances such as carbon, a fuel, and oxygen, an oxidant. A common oxidant is molecular oxygen, or O2, the product of photosynthesis.

"Microbes on Earth can use a dozen different types of fuels and a dozen different oxidants, although animals and plants and fungi all use molecular oxygen as their oxidant," Chyba says.

The dark depths of the Jovian satellites would hardly support photosynthesis. But two other chemical processes could produce supplies of O2, say Chyba and his colleague Kevin Hand of Stanford University.

Fast moving particles, accelerated by Jupiter's strong magnetosphere, frequently slam into Europa's icy surface. The collisions form H2O2 and O2, which could provide energy for interior life if the churning surface pushes down the oxidants.

"We can't be certain at this point whether the oxidants would actually make it into the water, even over geological time scales," says Chyba. "But if not, there are other mechanisms that might be a source for molecular oxygen in the oceans."

One such alternative source of O2 is the deterioration of a radioactive form of potassium, located in the crust and ocean. As the potassium isotope decays, it divides water molecules and creates O2. While it wouldn't produce as much fuel as the bombarding particles, it could still make enough to support life, say the researchers.

"Obviously, we don't know if life exists on these moons," Chyba says. "But at least we can say that if the oceans are there, the compounds that could supply energy for life seem likely to be present."

Astronomers might have to wait awhile for more clues in the search for life. The earliest another mission could launch for the Jupiter system is 2008.





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• Galileo Project Home
• Photo Gallery: Jupiter
• The Nine Planets
• NASA Home Page

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