The Cassini spacecraft perceived the presence of hydrogen in the gas plumes and other materials, which were emanating from Enceladus.

The new research suggests that Saturn's this moon has a chemical energy source capable of supporting life.

Zurbuchen added that the missions were getting humans closer to understanding whether they were "indeed alone or not".

"The abundance of H2, along with previously observed carbonate species, suggests a state of chemical disequilibria in the Enceladus ocean that represents a chemical energy source capable of supporting life", Jeffrey Seewald, of the Marine Chemistry and Geochemistry Department at the Woods Hole Oceanographic Institution in MA, wrote in an accompanying "Perspectives" piece in the same issue of Science. From additional Cassini observations, scientists concluded that not only is there a pool of water near the south pole of Enceladus to generate the plumes, but a global ocean that lies beneath the moon's ice.

In fact, Enceladus may have methane breathing alien life already there.

The latest findings suggest that Enceladus - a small, icy moon a billion miles farther from the sun than Earth - has almost all of these ingredients for habitability.

While some ingredients for life were found on Enceladus, the scientists made clear that the discovery didn't confirm life on the planet, but merely confirmed favorable conditions.

"We're moving towards Enceladus's ocean being habitable, but we're not making any claims at this point about it being inhabited", lead author Hunter Waite, with the Southwest Research Institute in San Antonio, Texas, said in an interview.

In addition, Hubble Space Telescope researchers reported in The Astrophysical Journal Letters that they've spotted the same vapor jets erupting from Jupiter's large, icy moon Europa, which also has a liquid ocean beneath its icy crust. However, the scientists believe that phosphorus and sulphur might be existing on the moon.

Like Enceladus, Europa harbors a subsurface saltwater ocean and could contain organic molecules.

"Some of the most primitive metabolic pathways utilized by microbes in these environments involve the reduction of carbon dioxide (CO2) with H2 to form methane (CH4) by a process known as methanogenesis", Jeffrey Seewald wrote in an accompanying piece in the same Science magazine. An ecosystem like this is powered by chemical reaction rather than by reaction to sunlight - important because Saturn is so far from the sun and the ocean water of Enceladus is protected by a thick shell of surface ice.

NASA used a similar end-of-mission strategy for the Galileo spacecraft that explored Jupiter and its moons in the 1990s.

"That's just going to be a tremendous opportunity to test our theories and see if there's life there", said James L. Green, director of planetary science at NASA.

NASA is now planning to send the Europa Clipper mission, which will orbit around Jupiter and fly at least 40 times near Europa.

Two long running Nasa missions, the Hubble Space Telescope and the Cassini mission to Saturn, are providing the evidence necessary for further scientific investigations into extraterrestrial life.

NASA doesn't usually hold news conferences for minor discoveries or observations, so when the agency announced that it would be holding a press conference this week to talk about oceans on other planets, we knew it had to be something particularly interesting.