How JWST could find signs of alien life in exoplanet atmospheres

The James Webb Space Telescope can peer into alien skies like never before. With six potentially habitable planets within its sights, astronomers are entering a new era in the search for biology beyond our solar system

By Stuart Clark

WHEN the first observations from the James Webb Space Telescope (JWST) were made public in July 2022, the images of deep space were so breathtakingly beautiful that it was easy to overlook the dowdy-looking graph released alongside them. The world was agog at the majestic panoramas of clouds of gas and dust from which stars are born, and the shining spiral shapes of ludicrously distant galaxies. Yet for many astronomers, the graph, a simple curving line, was just as jaw-dropping. It heralded a new era in the search for alien life.

Showing the unambiguous detection of water vapour in the atmosphere of an exoplanet called WASP 96b, it was the first proof that this powerful telescope would be able to deliver what many had doubted, namely, precise details of the contents of atmospheres on worlds beyond our solar system. Just as the beauty of some of those deep-field images captured the imaginations of the public, the quality of this unprecedented graph electrified astronomers. Suddenly, it was clear we really can peer into alien skies like never before. Finally, we have a fighting chance of spotting the subtle signals that would prove life exists elsewhere – not that it will be easy.

Now, astronomers are plotting their next moves. Having whittled down the most promising planets, they are lining up observing time with JWST to probe their atmospheres, thinking again about what signs of life we should be looking for – and sizing up the prospects of success. “I feel like we’re at the beginning of a really exciting journey,” says …