It might look like a frozen wasteland, but scientists believe that beneath the inhospitable surface of Saturn’s moon Enceladus, life could be thriving in warm underground seas.
Nasa’s Cassini spacecraft has picked up the first evidence that chemical reactions occurring deep below the ice could create an environment capable of supporting microbes – or living organisms.
Experts said the discovery was “the last piece” in the puzzle which proved that life was possible on Enceladus, a finding all the more remarkable because the small moon is 1.43 billion kilometres from the sun. David Rothery, professor of planetary geosciences at the Open University, said: “At present, we know of only one genesis of life, the one that led to us.
“If we knew that life had started independently in two places in our solar system, then we could be pretty confident that life also got started on some of the tens of billions of planets and moons around other stars in our galaxy.”
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Liquid oceans exist miles below the surface on Enceladus, so to find out what is happening in the underground seas scientists must rely on the plumes of spray that shoot up into the atmosphere through cracks in the ice.
In October 2015, Nasa sent Cassini into a deep dive through one of those plumes and discovered hydrogen and carbon dioxide.
In a report of their findings published today in the journal Science, scientists said that the “only plausible” source for the hydrogen was chemical reactions between warm water and rocks on the ocean floor. Crucially, if hydrogen is present, it can mix with carbon dioxide to form methane, which is consumed by microbes in the deep, dark seas of our own planet.
Prof Hunter Waite, an investigator for Cassini’s mass spectrometer, which detected the hydrogen, said: “The plume contains chemical signatures of water-rock interaction between the ocean and a rocky core. The most plausible source of this hydrogen is ongoing hydrothermal reactions of rock containing reduced minerals and organic materials. On the modern Earth, geochemically derived fuels such as hydrogen support thriving ecosystems even in the absence of sunlight.”
Enceladus is the sixth-largest moon of Saturn. It is around 500km in diameter and approximately 1.3 billion kilometres from Earth.
The results are the strongest indication yet that Enceladus has all the conditions needed for life to form. If life is present, it could resemble single-celled tube-like extremophiles, which have lived in hydrothermal vents on Earth for billions of years.
Prof Rothery said: “We do now have the last piece of evidence needed to demonstrate that life is possible there. This is life that needs neither oxygen nor sunlight, and may be the form in which life on Earth began.”
Dr David Clements, an astrophysicist at Imperial College London, said: “This discovery does not mean that life exists on Enceladus, but it is a step on the way to that result.”
– The Telegraph, London
Nasa announce Saturn moon's subterranean seas could support organisms by: Elie Abi Younes published: