Why finding alien life in Universe is now 'only a matter of time'

Many astronomers are no longer asking whether there is life elsewhere in the Universe. The question on their minds is instead: when will we find it?

Many are optimistic of detecting life signs on a faraway world within our lifetimes - possibly in the next few years. One scientist, leading a mission to Jupiter, goes as far as saying it would be "surprising" if there was no life on one of the planet's icy moons.

Nasa's James Webb Space Telescope (JWST) recently detected tantalising hints at life on a planet outside our Solar System - and it has many more worlds in its sights. Numerous missions that are either underway or about to begin mark a new space race for the biggest scientific discovery of all time.

"We live in an infinite Universe, with infinite stars and planets. And it's been obvious to many of us that we can't be the only intelligent life out there," says Prof Catherine Heymans, Scotland's Astronomer Royal. "We now have the technology and the capability to answer the question of whether we are alone in the cosmos."

Telescopes can now analyse the atmospheres of planets orbiting distant stars for signs of chemicals that, on Earth at least, can be produced only by living organisms. The first flicker of such a discovery occurred earlier this month with the possible sign of a gas that is produced by simple marine organisms on Earth in the atmosphere of a planet named K2-18b, which is 120 light years away.

The planet is in what astronomers call ''the Goldilocks zone' - the right distance away from its star for the surface temperature to be neither too hot, nor too cold, but just right for there to be liquid water, which is essential to support life.

The team expects to know in a year's time whether the tantalising hints they have obtained are confirmed or have gone away.

Prof Nikku Madhusudhan, of the Institute of Astronomy at Cambridge University, who led the study, said that if the hints are confirmed "it would radically change the way we think about the search for life".

"If we find signs of life on the very first planet we study, it will raise the possibility that life is common in the Universe."

Even if they don't find life signs on K2-18b, the team has 10 more Goldilocks planets on their list to study and possibly many more after that.

Prof Madhusudhan predicts that within five years there will be what he describes as "a major transformation" in our understanding of planetary habitability and life in the Universe.

"By then we will have had the chance to study half a dozen planets like K2-18b or ones that are slightly hotter.

"It is possible that we are close to having the first detection. On the other hand, having no detection on any of them would also provide important insights into the possibility of life on such planets."