Life might be existing in the ocean of Saturn's moon, Enceladus.
This is the closest scientists have come to identifying a place having the ingredients for life, said Thomas Zurbuchen, the associate administrator of the NASA Science Mission Directorate.
Writing in the journal Science, the USA team led by Dr Hunter Waite, from the Southwest Research Institute in San Antonio, Texas, concluded: "Our analysis supports the feasibility of methanogenesis as an energy-releasing process that can occur over a wide range of geochemical conditions plausible for Enceladus' ocean". Combined with carbon dioxide, the hydrogen could provide the right conditions for life "as we know it", according to NASA. "We now know Enceladus has almost all the ingredients needed for life as we know it", said NASA.
This photo of Saturn's moon Enceladus, taken by the Cassini spacecraft, shows the cracks in the icy surface. NASA just revealed that Enceladus, a moon of Saturn, appears to have everything it needs to support oceanic life.
"The hydrogen is coming from a hydrothermal vent on the sea floor of Enceladus, going out into space in the plume", said Linda Spilker, Cassini project scientist at the Jet Propulsion Laboratory in Pasadena, California. "It would be like a candy store for microbes", says lead author Hunter Waite.
The findings were announced along with observations by the Hubble Space Telescope of another, much older moon - evidence of plumes spraying out of the surface of Jupiter's Europa. In fact, scientists hadn't realized that the venting plume on Enceladus existed until the mission detected it 12 years ago.
In 2015, the American space agency's Cassini probe made a deep dive into a geyser-like plume of water and other material erupting from cracks in the south polar region of Enceladus.
The discovery makes Enceladus the only place - apart from Earth - where a local energy source for life has been discovered.
Enceladus, a moon of Saturn, may harbor life analogous to that which exists near the hydrothermal vents in Earth's oceans.
Older results have suggested that the hot water is intermingling with the rock underneath the sea. But based on prior observations of the traces in Enceladus' plumes, Cassini's mission scientists wanted to know whether there was evidence of hydrothermal activity in the form of hydrogen.
The hydrogen in the sub-surface ocean could combine with carbon dioxide molecules in a process known as "methanogenesis", which creates a byproduct of methane. The Hubble space telescope is observing Europa from a distance for evidence of plumes of water, similar to the ones seen on Enceladus. This will end with Cassini burning up in Saturn's atmosphere. Close-up measurements will have to wait until the 2020s when NASA plans to launch missions whose entire objective is investigating Europa.
"If there are plumes on Europa, as we now strongly suspect, with the Europa Clipper we will be ready for them", said Jim Green, Director of Planetary Science, at NASA Headquarters.