Scientists have detected what they say is the strongest evidence yet that life may exist beyond Earth. A Cambridge University team studying the planet K2-18b found signs of molecules associated with simple organisms.

Lead researcher Professor Nikku Madhusudhan said: “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 James Webb Space Telescope detected chemical traces such as dimethyl sulphide, a gas produced by marine plankton on Earth.

Researchers estimate the level of this gas could be thousands of times higher than found in Earth’s atmosphere.

K2-18b lies 700 trillion miles away and is about 2.5 times Earth’s size, orbiting a red dwarf star.

Some scientists believe the planet contains a vast ocean, though others suggest molten rock or a gas giant structure.

More data is needed to confirm the signal and rule out non-biological explanations.

While cautious not to overstate the case, Prof Madhusudhan stressed the strength of the data – gathered using a different instrument and a distinct wavelength range from the team’s earlier observations.

He added: "This is a transformational moment in the search for life beyond the solar system, where we have demonstrated that it is possible to detect biosignatures in potentially habitable planets with current facilities. We have entered the era of observational astrobiology. The signal came through strong and clear.”

The presence of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) – gases that on Earth are produced exclusively by life – points to a scenario consistent with a living, ocean-covered Hycean world.

He added: “Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have.”

However, he emphasised the importance of scepticism, noting that until further data is collected and analysed, alternative explanations cannot be ruled out.

He added: “That’s how science has to work. We test, we verify, and only then do we claim certainty.”

The research was published in The Astrophysical Journal Letters.