Scientists found the ‘strongest evidence yet’ of life on a distant planet

Artwork of K2-18b, a faraway world that may be home to life

A team of scientists from the University of Cambridge has uncovered what they describe as the “strongest evidence yet” that life may exist on a distant planet orbiting another star. Using NASA’s powerful James Webb Space Telescope (JWST), researchers detected potential biosignatures in the atmosphere of a planet called K2-18b.

“This is the strongest evidence yet there is possibly life out there,” said lead researcher Professor Nikku Madhusudhan. “I can realistically say that we can confirm this signal within one to two years,” he told the BBC from Cambridge University’s Institute of Astronomy.

K2-18b is located 124 light-years, or about 700 trillion miles, from Earth. The planet is two-and-a-half times the size of Earth and orbits a small red star. The JWST was able to analyze the planet’s atmosphere using the light that passes through it from its sun.

According to BBC, what the team discovered were signs of molecules dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) – gases on Earth that are only produced by simple life forms like marine phytoplankton and bacteria. According to Professor Madhusudhan, the quantity of these gases in K2-18b’s atmosphere was unexpectedly high.

“The amount we estimate of this gas in the atmosphere is thousands of times higher than what we have on Earth,” he explained. “So, if the association with life is real, then this planet will be teeming with life.”

He went even further: “If we confirm that there is life on K2-18b, it should basically confirm that life is very common in the galaxy.”

Dr. Subir Sarkar, an astrophysicist at Cardiff University and part of the research team, said the planet may contain an ocean potentially full of life – though he cautioned that scientists “don’t know for sure.”

Still, the evidence remains tentative. Professor Madhusudhan noted that while the latest results are encouraging, they only reach a three-sigma level of certainty – about 99.7% – which falls short of the five-sigma (99.99999%) standard needed to claim a scientific discovery.

“There is still a 0.3% chance that it might be a statistical fluke,” he told BBC, adding that the team aims to bring that down to less than one in a million. “So we want to be really, really thorough, and make more observations.”

Even if that level of certainty is reached, scientists remain cautious. Professor Catherine Heymans of the University of Edinburgh and Scotland’s Astronomer Royal said, “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.”

Cambridge researchers are working with other labs to determine if DMS and DMDS can be produced through non-biological processes.

There’s also debate over the planet’s structure. Some suggest an ocean is absorbing ammonia, implying liquid water. Others, like Professor Oliver Shorttle, argue it could be an ocean of molten rock. Dr. Nicolas Wogan of NASA’s Ames Research Center proposes K2-18b might be a gas giant with no surface at all.

Despite the uncertainties, Professor Madhusudhan remains optimistic. “Decades from now, we may look back at this point in time and recognize 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 findings are published in The Astrophysical Journal Letters. MDT