Scientists have found evidence that there is life on Saturn’s biggest moon, Titan.
They have discovered clues that primitive aliens are breathing in Titan’s atmosphere and feeding on fuel at the surface.
The startling discoveries, made using an orbiting spacecraft, are revealed in two separate reports.
Data from Nasa’s Cassini probe has analysed the complex chemistry on the surface of Titan – the only moon known to have a dense atmosphere.
Its surface is covered with mountains, lakes and rivers which has led astronomers to call it the most Earthlike world in the solar system.
Organic chemicals had already been detected on the 3,200-mile wide planet. But the liquid on Titan is not water but methane and the scientists expect life there to be methane-based.
The first paper, in the journal Icarus, shows that hydrogen gas flowing down through Titan’s atmosphere disappears at the surface, suggesting it could be being breathed by alien bugs.
The second paper, in the Journal of Geophysical Research, reports there is a lack of a certain chemical on the surface, leading scientists to believe it may be being consumed by life.
Scientists had expected sunlight interacting with chemicals in the atmosphere to produce acetylene that falls down to coat Titan’s surface. But Cassini detected no acetylene there.
Experts warn that there could be other explanations for the results.
But taken together, they fulfil two important conditions necessary for methane-based life to exist.
Nasa astrobiologist Chris McKay said: ‘If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth.’
Scientists believe that when the Sun swells up, swallowing Earth, conditions could be ideal on a warmer Titan.
Professor John Zarnecki, of the Open University, said: ‘We believe the chemistry is there for life to form. It just needs heat and warmth to kick-start the process.
‘In four billion years’ time, when the Sun swells into a red giant, it could be paradise on Titan.’