Are we alone? Discovery on planet K2-18b brings alien life closer to reality

Towards the end of his life, the cosmologist Stephen Hawking was asked about the odds of finding intelligent alien life in the next two decades. “The probability is low,” he declared in 2016, and took a pause before adding: “Probably.”

- Ian Sample

Last week, other scientists from the University of Cambridge reported tentative evidence for the presence of two compounds in the atmosphere of a planet, K2-18b, that sits in the constellation of Leo, 124 light years away.

On Earth, dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) are hallmarks of life, emanating only from microscopic organisms. And while marine phytoplankton might not rank as particularly intelligent, the claim unleashed a wave of excitement: the answer to the question “are we alone?” has never seemed closer.

“This is the strongest evidence to date for a biological activity beyond the solar system,” said Prof Nikku Madhusudhan, an astrophysicist in the team. “Decades from now, we may look back at this point in time and recognise it was when the living universe came within reach.”

Two more years of observations with the James Webb Space Telescope (JWST) will nail down whether or not the compounds really exist in K2-18b’s atmosphere, Madhusudhan believes.