Chemistry of company: Scientists find molecules linked to life on planet 124 light years away

Scientists are saying that there are signs that life may exist on a distant giant planet, K2-18 b, located 124 light years away from our Earth, The Guardian reported.

The James Webb Space Telescope has detected two rare chemicals, typically produced by living organisms on Earth, raising hopes that life could exist beyond our solar system.

These chemicals, dimethyl sulphide (DMS) and dimethyl disulphide (DMDS), do not directly prove the existence of alien life, but their presence could be a major step towards answering the age-old question: are we alone in the universe, or is there evidence of life elsewhere in the universe?

“This is the strongest evidence to date for biological activity beyond the solar system,” said Professor Nikku Madhusudhan, an astrophysicist at the University of Cambridge who led the observations. “We are being very cautious. We have to question ourselves, both whether the signal is real and what it might mean.”

She said, “In the future, we may look back and realise this was the moment when the possibility of life beyond Earth came within reach. This could be the turning point where we finally have the chance to answer the question of whether we’re alone in the universe.”

Doubts remain over habitability, chemical clues on K2-18 b

Some experts are more sceptical, questioning whether the conditions on K2-18 b are truly suitable for life, and whether DMS and DMDS, substances largely produced by marine plankton on Earth, can be considered reliable signs of life.

K2-18 b, located in the Leo constellation, is nearly nine times the mass of Earth and 2.6 times larger. It orbits within the habitable zone of its star, a cool red dwarf smaller than the Sun. In 2019, the Hubble Space Telescope appeared to detect water vapour in its atmosphere, leading scientists to label it the “most habitable known world” beyond our solar system.

However, follow-up observations by Madhusudhan’s team in 2023 revealed that the supposed water signal was actually methane. Even so, they argued that K2-18 b’s characteristics suggest it could still be a habitable world, possibly covered by a vast ocean, a view that remains under debate. More recently, the Cambridge team reported a potential sign of DMS.

Planets outside our solar system are too distant to photograph or explore with spacecraft.

However, scientists can estimate their size, density, and temperature and study their chemical composition, by tracking the planet as it passes in front of its star and analysing the starlight filtered through its atmosphere.

In the latest observations, they noticed that wavelengths absorbed by DMS and DMDS dropped sharply as K2-18 b moved across the face of its star.

“The signal came through strong and clear,” said Madhusudhan. “If we can detect these molecules on habitable planets, this is the first time we’ve been able to do that as a species … it’s mind-boggling that this is possible.”

The findings, published in The Astrophysical Journal Letters, suggest that the levels of DMS, DMDS, or both (which have similar chemical signatures) on K2-18 b could be thousands of times higher than those on Earth. The results are statistically significant—with only a 0.3 per cent chance of being random, but still fall short of the gold standard for a confirmed discovery in physics.

“There might be unknown processes creating these molecules,” said Madhusudhan. “But at present, we don’t know of any explanation that doesn’t involve life.”

One challenge is that scientists still disagree about the planet’s environment. While the Cambridge team believes K2-18 b may be covered by a deep ocean, others argue it could be a gas planet, or have oceans of magma rather than water.