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.
The vapor or gas contains hydrogen, one of the essential components of life.
NASA's space Hubble telescope has observed "probable" plumes erupting from Jupiter's moon Europa.
Cassini has been orbiting Saturn since 2004 and is in its last months of life. The Hubble team has published additional evidence of plumes of water erupting from the surface of Europa, a moon of Jupiter. The Cassini spacecraft had occasion to descend into a plume of gas and water in October, 2015.
Illustration showing Cassini above the plumes of Enceladus. The microbes could combine the carbon dioxide in water and hydrogen to gain energy. When Cassini-Huygens passed through those plumes, it found "that hydrogen is coming from a hydro-thermal vent on the seafloor of Enceladus, going out into space in the plume", according to Dr. Linda Spilker, a Cassini-Huygens project scientist. Two chemicals essential to living organisms sulfur and phosphorus have not been confirmed, but all the same, Enceladus is rising to the top of habitable places that exist in the solar system..
It will be up to future spacecraft to prove that point, however. In September, it will plunge into the planet and end its journey. The scientists believe the gas is likely produced by a chemical reaction involving hydrothermal vents at the bottom of the moon's ocean.
One of Saturn's small, white moons has the ideal conditions for life in its icy crust-covered ocean.
Scientists will have a chance to explore Europa's watery world as NASA prepares for the Europa Clipper mission.More news: Iran's Ahmadinejad sees no threat from US
NASA's Galileo spacecraft orbited Jupiter for many years (1995-2003), but Europa was not a main target of its investigations and only about a dozen flybys of the moon were made. The data show about 1 percent of the plume material is hydrogen.
Some of the material falls back onto the surface as a fresh coat of ice, while much of the rest gathers into a halo of ice dust that feeds one of Saturn's rings.
William Sparks, a researcher at NASA's Space Telescope Science Institute, said the showers were spotted in 2014. They are nearly the same place at that point in time. NASA's carefully worded press release makes clear that scientists remain uncertain that the plumes are there, however, saying the 2016 images "bolster evidence" that the plumes "could be a real phenomenon".
Because that region of the solar system traps atomic particles from the sun, the radiation of the area around Jupiter is risky to spacecraft. NASA now has a spacecraft orbiting Jupiter, Juno, but it is not created to study Europa either.
The Europa Clipper, named for the innovative, streamlined ships of the 1800s, will launch in the 2020s and arrive at Europa after a few years.
Hubble's identification of a site which appears to have persistent, intermittent plume activity provides a tempting target for the Europa mission to investigate with its powerful suite of science instruments. "My money for the moment is still on Europa", she says.