JWST could soon tell us what exoplanets' surfaces are made of

Observing the surface of an exoplanet is tricky, but a study analysing data from the Spitzer space telescope suggests it should be feasible with the more powerful James Webb telescope

By Alex Wilkins

The James Webb Space Telescope (JWST) may be able to give us a tantalising glimpse of the surfaces of rocky planets outside our solar system, as well as their atmospheres.

One way of measuring the atmosphere of a distant planet is to watch as it passes, or transits, in front of its star. As light passes through the atmosphere, molecules will absorb certain wavelengths of light, helping astronomers to figure out its composition.

Measuring the surface of a planet is trickier. Any light reflecting off …