LOS ANGELES (Xinhua): U.S. scientists have made the first-ever detection of an organic molecule on an extra-solar planet, marking the first step toward identifying signs of life outside the solar system, according to an announcement Wednesday.

Using the Hubble Space Telescope, scientists led by a Jet Propulstion Laboratory (JPL) astronomer discovered in the atmosphere of a distant Jupiter-sized planet a molecule of methane, which experts said plays a potentially key role in prebiotic chemistry -- chemical reactions necessary to life formation.

"This is a crucial stepping stone to eventually characterizing prebiotic molecules on planets where life could exist," said Mark Swain of the Los Angeles-based JPL.

The atmospheric temperature of the planet, HD 189733b, is estimated at 1,700 degrees Fahrenheit and is thus unlikely to actually support life, the scientists said.

But the discovery is still being hailed for proving that the spectroscopy method, a technique that splits light into various components to reveal the "fingerprints" of various chemicals, can be used to search for organic molecules around other planets.

"This observation is proof that spectroscopy can eventually be done on a cooler and potentially habitable Earth-sized planet orbiting a dimmer red dwarf-type star," Swain said.

The findings have been published in Thursday's issue of the journal Nature.