Astronomers have detected what may be the strongest evidence yet of extraterrestrial life on K2-18b, a massive exoplanet orbiting a star 120 light-years from Earth. The research team, led by Cambridge astronomer Nikku Madhusudhan, published their findings today in the Astrophysical Journal Letters.
Using the James Webb Space Telescope, researchers found significant concentrations of dimethyl sulfide and dimethyl disulfide in K2-18b’s atmosphere. On Earth, these sulfur compounds are exclusively produced by living organisms, particularly marine algae. “It is in no one’s interest to claim prematurely that we have detected life,” said Madhusudhan, though he described the findings as “a revolutionary moment” and “the first time humanity has seen potential biosignatures on a habitable planet.”
The team detected the signals during two separate observations, with the second showing an even stronger signature. Their analysis suggests K2-18b may be a “Hycean” planet — covered with warm oceans and wrapped in a hydrogen-rich atmosphere — with concentrations of dimethyl sulfide thousands of times higher than Earth levels.
Other scientists remain cautious. Christopher Glein of the Southwest Research Institute suggested K2-18b could instead be “a massive hunk of rock with a magma ocean and a thick, scorching hydrogen atmosphere.” Further observations with Webb and future NASA telescopes will be necessary to confirm whether K2-18b is truly habitable or inhabited, though planned budget cuts may impact follow-up research.
Further reading: Water Found On a Potentially Life-Friendly Alien Planet (2019).
