There might be alien life in our own solar system, Nasa has announced.
All of the necessary things to support life have been found on one of the moons that orbits Saturn.
Enceladus has chemicals that when found on Earth tend to indicate life, suggesting that there might be living things under its icy shell.
Scientists have long thought of Enceladus as one of the prime candidates for life within our solar system, in large part because of its subsurface ocean that covers its entire body. But the new research gives the best look yet at that moon, showing that it has a chemical energy source capable of supporting life.
The new findings came from the Cassini spacecraft, which flew through a huge plume of water that was being shot out of the surface of Enceladus. As it did, the spacecraft took readings of the water and sent them back to Earth for further study.
That study found evidence of molecular hydrogen in those jets of vapour. That molecular hydrogen could only plausibly have come from hydrothermal reactions between hot rocks and water underneath the moon’s icy crust, the researchers claim.
On Earth, that same process provides energy for the ecosystems found around hydrothermal vents.
That hydrogen serves as an especially good food, and some of the most ancient life forms on Earth use it for fuel. The kind of life that may live on Enceladus would likely eat that hydrogen and then release methane – which has also been found coming from the moon.
Further research found that the material Cassini flew through also included large amounts of carbon dioxide. Molecular hydrogen and carbon dioxide are critical for the process of methanogenesis – a reaction that sustains microbes in similar dark, undersea environments on Earth.
Scientists think that three ingredients are needed for life on a planet: water, organic molecules and a source of energy. The first two have been detected on Enceladus before, but the new discovery means that all three key components are there, with the addition of a fuel source for keeping that life alive.
“We now know there’s not only a warm, wet environment – we now realise there’s food for life,” said Lewis Dartnell, an astrobiology researcher at the University of Westminster. “There’s fuel for an ecosystem on Enceladus.”
That ecosystem hasn’t been yet detected directly, but the new findings suggest that all of the pieces are in place for it to thrive.
“That’s what’s very significant here: this molecular hydrogen is a direct observation of an energetic process that is potentially capable of fuelling life,” said Caitriona Jackman from the University of Southampton.
One leading scientist called the new research “an important advance in assessing the habitability of Enceladus”. While noting that much work still needed to be done to understand the geological makeup of the moon, the new research helps “constrain the possibility of life elsewhere in our solar system”, geochemist Jeffrey Seewald wrote in an assessment of the work.
The work shows that humanity should send a mission specifically to Enceladus to hunt for signs of life, researchers said.
Professor Jackman, who worked on the Cassini mission, called the findings a “tantalising result” and called for further work to establish more about the icy moon. Professor Dartnell said that there are “some really profound discoveries awaiting us”.