Possible signs of life detected on distant planet, Cambridge researchers say

Astronomers at the University of Cambridge have uncovered fresh but inconclusive evidence suggesting the possible presence of life on a distant exoplanet orbiting another star.

Using data from NASA's James Webb Space Telescope (JWST), researchers have detected the presence of molecules in the atmosphere of exoplanet K2-18b that, on Earth, are solely produced by simple life forms. The findings mark the second time that such life-linked molecules have been observed on this planet, though the latest results appear significantly more promising, reports the BBC.

Professor Nikku Madhusudhan, who led the research at Cambridge University's Institute of Astronomy, expressed optimism about the findings. 

"This is the strongest evidence yet there is possibly life out there," he said. 

"I can realistically say that we can confirm this signal within one to two years."

Located approximately 700 trillion miles away, K2-18b is more than twice the size of Earth and orbits a cool red dwarf star. The JWST's advanced capabilities allow scientists to analyse the planet's atmosphere by observing starlight passing through it, revealing signs of specific chemicals.

The Cambridge team found traces of dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) in the atmosphere—compounds which, on Earth, are primarily emitted by marine phytoplankton and certain bacteria.

"The amount we estimate of this gas in the atmosphere is thousands of times higher than what we have on Earth," Prof Madhusudhan said. 

"So, if the association with life is real, then this planet will be teeming with life."

"If we confirm that there is life on K2-18b it should basically confirm that life is very common in the galaxy," he added. 

Despite the excitement, the researchers emphasise that more data is needed. 

The detection currently stands at a "three sigma" level of statistical confidence, meaning a 99.7% likelihood the signal is real. This falls short of the "five sigma" threshold (99.99999%) generally required by scientists to confirm a discovery.

The James Webb Space Telescope is powerful enough to analyse the atmosphere of planets that are hudreds of trillions of miles away. Photo: NASA

Professor Catherine Heymans, Scotland's Astronomer Royal and a physicist at the University of Edinburgh who is not involved in the research, cautioned against jumping to conclusions.

"Even with that certainty, there is still the question of what is the origin of this gas," she told BBC News. 

"On Earth it is produced by microorganisms in the ocean, but even with perfect data we can't say for sure that this is of a biological origin on an alien world because loads of strange things happen in the Universe and we don't know what other geological activity could be happening on this planet that might produce the molecules."

The Cambridge team shares this view. They are working with other scientists to explore whether the molecules in question could be generated through non-biological processes in controlled lab environments.

Alternative explanations continue to circulate within the scientific community. One theory proposes that K2-18b contains a vast ocean of liquid water that absorbs ammonia from the atmosphere, suggesting a habitable environment. However, other scientists argue that the absence of ammonia could be due to a molten rock ocean, which would make life impossible.

"Everything we know about planets orbiting other stars comes from the tiny amounts of light that glance off their atmospheres," said Professor Oliver Shorttle of Cambridge University. 

"So it is an incredibly tenuous signal that we are having to read, not only for signs of life, but everything else. With K2-18b, part of the scientific debate is still about the structure of the planet."

Dr Nicolas Wogan at NASA's Ames Research Center has proposed another hypothesis: that K2-18b is actually a mini gas giant lacking any surface, again casting doubt on its potential for hosting life.

Yet, despite the scientific uncertainty, Prof Madhusudhan remains hopeful.

"Decades from now, we may look back at this point in time and recognise it was when the living universe came within reach," he said. 

"This could be the tipping point, where suddenly the fundamental question of whether we're alone in the universe is one we're capable of answering."

The full findings have been published in The Astrophysical Journal Letters.