The discovery comes as the Cassini spacecraft is nearing the end of its 13-year mission to Saturn.
The second-largest planet in the solar system, Saturn has long been a subject of fascination with its spectacular series of thousands of rings around the giant gassy planet.
But, now, it is one of its moons, Enceladus, that has scientists excited.
Crucially, within those ocean worlds on Enceladus, NASA says a form of chemical energy which life can feed on appears to exist.
NASA says life, as we know it, requires three primary ingredients -- liquid water, a source of energy for metabolism, and the right chemical ingredients, such as hydrogen.
Meanwhile, an astronomer at the Space Telescope Science Institute says one of four major moons of the solar system's biggest planet, Jupiter, could have similar characteristics.
William Sparks says NASA's Hubble Telescope has captured what could be evidence of water erupting from the moon Europa.
The findings from both Saturn's and Jupiter's moons are now laying the groundwork for NASA's future Europa Clipper mission, planned for launch in the 2020s.
The small, icy moon is over one-and-a-half billion kilometres further from the sun than Earth.
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