Scientists announced yesterday the strongest evidence yet for possible alien life after detecting gases in a distant planet’s atmosphere that, on Earth, are only produced by living organisms.
The James Webb Space Telescope detected dimethyl sulfide and dimethyl disulfide in the atmosphere of planet K2-18 b, according to a study published in the Astrophysical Journal Letters and reported by Reuters.
These gases are produced on Earth exclusively by biological processes, primarily by algae.
Located approximately 124 light-years from Earth, K2-18 b is 8.6 times Earth’s mass and orbits in the “habitable zone” of a red dwarf star where liquid water could exist.
The gases were detected with a 99.7% confidence level, meaning there’s still a 0.3% chance the observation could be a statistical fluke.
“This is a transformational moment in the search for life beyond the solar system,” said astrophysicist Nikku Madhusudhan of Cambridge University, who led the study. “We have entered the era of observational astrobiology.”
Scientists stress this finding should be viewed cautiously, with Madhusudhan noting it’s “in no one’s interest to claim prematurely that we have detected life.” Additional observations are needed to rule out non-biological explanations.
The planet could potentially be a “hycean world” – covered by a liquid water ocean with a hydrogen-rich atmosphere.
“The only scenario that currently explains all the data obtained so far is one where K2-18 b is a hycean world teeming with life,” Madhusudhan explained.
The research team’s detection involved analyzing starlight passing through K2-18 b’s atmosphere using Webb’s highly sensitive instruments.
The gases were detected at concentrations “thousands of times higher than their concentrations in the Earth’s atmosphere, and cannot be explained without biological activity based on existing knowledge,” according to Madhusudhan.
Christopher Glein, principal scientist at the Southwest Research Institute in Texas, emphasized the need for caution when interpreting these results.
“The rich data from K2-18 b make it a tantalizing world,” said Glein. “Yet, we must be very careful to test the data as thoroughly as possible.”
To conclusively determine whether these gases indicate the presence of life, scientists plan to conduct additional observations.
“First we need to repeat the observations two to three times to make sure the signal we are seeing is robust and to increase the detection significance,” Madhusudhan explained, noting that researchers aim to reduce the odds of a statistical fluke to below one in a million.
This detection represents what Madhusudhan calls a “transformational moment” in our search for extraterrestrial life, moving humanity closer to answering whether we are alone in the universe – a question that has fascinated mankind for millennia.
