Washington, April 14 (IANS) Saturn's icy moon Enceladus has a form of chemical energy that life can feed on, researchers with NASAs Cassini mission to Saturn have revealed.
"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 NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.
In a separate study, scientists also reported additional evidence of water vapour plumes erupting from Jupiter's moon Europa.
Together, the findings suggest that these active ocean worlds in our solar system are worth more exploration in our search for life beyond the Earth.
The study from researchers with the Cassini mission, published in the journal Science, indicates hydrogen gas -- which could potentially provide a chemical energy source for life -- is pouring into the subsurface ocean of Enceladus from hydrothermal activity on the seafloor.
The presence of ample hydrogen in the moon's ocean means that microbes -- if any exist there -- could use it to obtain energy by combining the hydrogen with carbon dioxide dissolved in the water.
This chemical reaction, known as "methanogenesis" because it produces methane as a byproduct, is at the root of the tree of life on the Earth, and could even have been critical to the origin of life on our planet.
Life as we know it requires three primary ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, primarily carbon, hydrogen, nitrogen, oxygen, phosphorous and sulphur.
With this finding, Cassini has shown that Enceladus -- a small, icy moon a billion miles farther from the Sun than the Earth -- has nearly all of these ingredients for habitability.
Cassini has not yet shown phosphorous and sulphur are present in the ocean, but scientists suspect them to be, since the rocky core of Enceladus is thought to be chemically similar to meteorites that contain the two elements.
The Cassini spacecraft detected the hydrogen in the plume of gas and icy material spraying from Enceladus during its last, and deepest, dive through the plume on October 28, 2015.
Cassini also sampled the plume's composition during flybys earlier in the mission.
From these observations scientists have determined that nearly 98 per cent of the gas in the plume is water, about one per cent is hydrogen and the rest is a mixture of other molecules including carbon dioxide, methane and ammonia.
At the same time, NASA scientists have also reported additional evidence of water vapour plumes erupting from Jupiter's moon Europa.
The paper detailing new Hubble space telescope findings, published in The Astrophysical Journal Letters, reports on observations of Europa from 2016 in which a probable plume of material was seen erupting from the moon's surface at the same location where Hubble saw evidence of a plume in 2014.
These images bolster evidence that the Europa plumes could be a real phenomenon, flaring up intermittently in the same region on the moon's surface.
Researchers speculate that, like Enceladus, this could be evidence of water erupting from the moon's interior.
NASA's will send a probe called Europa Clipper mission, which is planned for launch in the 2020s, to search signs of life on the Jupiter's moon by flying through those plumes.
"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.