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Nasa spacecraft Cassini detects signs that one of Saturn’s moons, Enceladus, may be able to support life.
VIDEO: Julian Huget provides a summary of Cassini’s passage through Enceladus’ plumes.
A tiny moon of Saturn has most of the conditions necessary for life, Nasa announced on Thursday. They unveiled a discovery from an underground ocean that makes the world a leading candidate for organisms as humans know them.
Scientists stressed that the discovery on a moon named Enceladus is not evidence that life has in fact developed on another world, but they have managed to establish the existence of water, chemistry and energy sources that are necessary for it.
“We now know that Enceladus has almost all of the ingredients that you need to support life as we know it on Earth,” said project scientist, Linda Spilker.
Beneath its frozen surface, Enceladus has a saltwater ocean, and the hydrogen – produced in a reaction between heated water and rocks – indicates that the moon has active energy sources, possibly akin to the undersea vents that teem with life on planet Earth.
DIAGRAM: Dissecting Saturn’s moon, Enceladus, to reveal the saltwater ocean beneath its frozen surface.
The spacecraft Cassini detected the hydrogen in the fall of 2015, when it flew through a plume of vapour that had been spewed out through cracks in the moon’s icy surface. The flyby discovered water, ice, traces of methane, salts and other carbon compounds, the researchers said.
“If you were a micro-organism, hydrogen would be like candy – it’s your favourite food,” explained Dr Chris McKay, an astrobiologist with the US space agency.
“It’s very good energetically; it can support micro-organisms in grand style. Finding hydrogen is certainly a big plus; icing on the cake for the habitability argument, and a very tasty one at that.”
AUDIO: Spilker explains why the uncovering of hydrogen on the moon is of significance.
“This finding does not mean that life exists there, but it makes life more plausible and potentially quite abundant if a fraction of the hydrogen is used to drive biology,” said Jeffrey Kargel, a professor at the University of Arizona.
Still, the presence of hydrogen does not prove that life exists on Enceladus. It might suggest the opposite.
At hydrothermal vents on Earth, the hydrogen is quickly gobbled up by microbes. That so much hydrogen is rising through Enceladus’s ocean and reaching space could mean there is no life on the little moon to take advantage of it.
“If you have those stacks of pizzas, they disappear,” said Mary A. Voytek, head of Nasa’s astrobiology program.
Nevertheless, Andrew Coates, a professor of physics at University College London, said: “This distant moon now joins Mars and Europa as the best potential locations for life beyond Earth in our solar system.”
Nasa has found liquid on mars, but solar winds have for eons stripped away its atmosphere and the planet has dried out into its current irradiated state. Like Enceladus, Europa, a moon of Jupiter, has an icy crust and an underground ocean. Nasa hopes to send a probe to the moon in the 2020s, complete with instruments to detect heat and penetrate ice in search of undersea vents.
Cassini, which is running out of fuel, will end its 20-year mission to Saturn and its moons later this year, with a final journey between Saturn’s rings and then a fiery disintegration into the planet’s storms.
The scientists plan to destroy Cassini on Saturn in part to prevent the spacecraft from crashing on Enceladus, where it could contaminate life there – if, that is, it exists.