Life May Exist On Planets
In Deep Space
By Jennifer Viegas
Discovery News Brief

Life-sustaining conditions may exist on planet-like bodies in deep, interstellar space, according to a California Institute of Technology scientist.
In a paper published in the current journal Nature, David J. Stevenson, professor of planetary science, draws on planetary theory and his own calculations to explain how conditions supporting life could exist beyond the known solar system.
Stevenson,s theory is based upon a widely known planet dispersal model. It states that Earth may have had one or more siblings when the solar system was born, but they were jettisoned by gravity when they got too close to Jupiter or other large planets.
Stevenson believes these wandering planets are surrounded by a blanket of hydrogen. He says hydrogen normally is transparent, but when it reaches a high enough temperature it can absorb infrared light and become opaque.
"This opaque hydrogen layer could create a greenhouse effect that may very well sustain oceans, " says Stevenson. "Scientists call it the Goldilocks, scenario -- where conditions are neither too hot, nor too cold."
Although Stevenson says such rogue planets would derive little or no energy from the sun, he believes that temperature and chemical differences created by volcanic eruptions and lightning would create an unstable environment that could produce a form of k inetic energy.
"Life depends on the availability of free energy," he explains, "so it,s possible that organisms without sunlight could develop and be sustained by energy resulting from these forces."
He says it's unclear exactly how organisms could take in the energy, but extraterrestrial life probably wouldn't resemble any creature we know. Eyes, for example, would have to be adapted to darkness, as only a red glow would be emitted from the volcanoes .
Jack Lissauer, space scientist at NASA Ames Research Center, says theories like those proposed by Stevenson are important to current space exploration.
"We have to be careful about setting limits to space research," says Lissauer, "as it,s probable that life can survive in very unearthly environments."
Lissauer points out that NASA is currently planning a year 2003 mission to Europa, one of Jupiter,s moons, which is very dark, but that has an ocean thought to be composed of H20. "Like Stevenson,s model, life-sustaining water could exist below Europa,s surface," says Lissauer.