In 2024, the NASA astrophysicist Dr Amber Straughn told Dazed she was “very hopeful” that we’d find life on another planet in our lifetimes. This week, it appears we got a step closer, as researchers at Cambridge University revealed the “most promising signs yet” of life beyond our solar system, in the form of a chemical biosignature.

What is a biosignature, you ask? Essentially, it’s a chemical that can only be produced (as far as we know) by organic processes. These can be identified in distant planets’ atmospheres using scientific techniques like spectroscopy – basically, breaking down the starlight that passes through a planet’s atmosphere.

In this case, the possible biosignatures are dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS). These were spotted, by a team at the university’s Institute of Astronomy, in the atmosphere of the exoplanet K2-18b, which orbits its star in the habitable or ‘Goldilocks’ zone. On Earth, these chemical compounds are only produced by life, particularly microbial life like ocean-dwelling phytoplankton. This doesn’t rule out an unknown source pumping the molecules into K2-18b’s atmosphere, but the results definitely warrant further investigation.

Commenting on the new study in The Astrophysical Journal Letters, lead researcher Prof Nikku Madhusudhan tells the BBC: “This is the strongest evidence yet there is possibly life out there. I can realistically say that we can confirm this signal within one to two years.”

The observations have to be confirmed in case of statistical outliers. Right now, there’s a reported 0.3 per cent probability they occurred by chance, putting them at the ‘three-sigma’ level of statistical significance. To be marked an official scientific discovery, they need to pass the ‘five-sigma’ threshold with a 0.00006 per cent probability they occurred by chance – which is pretty much as close as scientists get to declaring something 100 per cent true. Around a day of (highly competitive) time with the James Webb Space Telescope could help reach this level of certainty.

And what if we do confirm that K2-18b holds signs of life? Well for starters, it’s about 124 light-years away (or 700 trillion miles), so we wouldn’t be popping over for tea anytime soon. It’s also about two-and-a-half times the size of our home planet, but the amount of possible biosignatures is surprisingly high by comparison. “The amount we estimate of this gas in the atmosphere is thousands of times higher than what we have on Earth,” says Madhusudhan. “So, if the association with life is real, then this planet will be teeming with life.”

This means that a confirmed discovery would be big, even if we couldn’t go to visit any little green men, because of its implications for the broader existence of alien life. As Madhusudhan adds: “If we confirm that there is life on K2-18b, it should basically confirm that life is very common in the galaxy.”