Hydrogen molecules were detected in vapour plumes emerging from cracks in Enceladus' surface.

"We now know that Enceladus has nearly all of the ingredients that you would need to support life as we know it on Earth", she said at a NASA news conference.

Since NASA didn't even know about Enceladus' plumes, its subsurface ocean, and the potential for hydrothermal activity there until after Cassini had arrived at Saturn, the spacecraft isn't equipped with the right instruments to take the investigation any further.

"Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth", said Linda Spilker, Cassini project scientist at JPL.

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.

"Most of us would be excited with any life", said Mary Voytek, an astrobiology senior scientist for NASA.

"The next time we go back. you're going to take something that not only picks up on the habitability story, but it starts looking for evidence for life". There, microbes don't receive energy from sunlight, but use methanogenesis, a process that reduces carbon dioxide with hydrogen, to form methane.

"Now, Enceladus is high on the list in the solar system for showing habitable conditions", said Hunter Waite, one of the study's leading researchers. Just like Enceladus, there's also an ocean beneath that moon's crappy surface.

The new findings, published in the USA journal Science, are an independent line of evidence that hydrothermal activity is taking place in the ocean of Enceladus, a small, icy moon a billion miles farther from the sun than Earth.

NASA and others are quick to point out this latest discovery does not mean there's life on Enceladus (ehn-SEHL'-uh-duhs), but that there may be conditions favorable for life.

All of the ingredients necessary for life are available Saturn's moon Enceladus. Other ocean worlds in our solar system, besides Europa and Enceladus, potentially include Jupiter's moons Ganymede and Callisto; Saturn's moons Mimas and Titan; Neptune's moon Triton; and the dwarf planet Pluto.

But we've also learned that life finds a way in the harshest of Earth's environments, like vents in the deepest parts of the ocean floor. Europa Clipper will fill in a lot of gaps in our understanding.

"This is the first time we've been able to make a calorie count of an alien ocean", he said. "It remains for a future mission to detect life at Enceladus".

The fact that these 300 pizzas per hour are being detected suggests life may not exist, she said. Sparks and his team are continuing to use Hubble to monitor Europa for additional examples of plume candidates and hope to determine the frequency with which they appear. Here's more info on that mission and Europa as a whole.

Europa Clipper will be launched around 2022, but a mission to Enceladus will have to wait a little longer.

The craft found that the moon's levels of carbon dioxide, methane and hydrogen were "out of equilibrium", which could actually lead to an energy source that could provide food for potential inhabitants.