Scientists have identified a promising new way to detect life on faraway planets, hinging on worlds that look nothing like Earth and gases rarely considered in the search for extraterrestrials.

In a new Astrophysical Journal Letters paper, researchers from the University of California, Riverside, describe these gases, which could be detected in the atmospheres of exoplanets—planets outside our solar system—with the James Webb Space Telescope, or JWST.

Called methyl halides, the gases comprise a methyl group, which bears a carbon and three hydrogen atoms, attached to a halogen atom such as chlorine or bromine. They’re primarily produced on Earth by bacteria, marine algae, fungi, and some plants.