NATIONAL GEOGRAPHIC - When inspecting the cosmos for potentially habitable worlds, scientists have long looked for the color green. Green is the fundamental color of life on Earth, after all. But what if life on faraway planets wasn’t green at all? In fact, what if it were purple?
Signatures of habitable worlds
Astronomers look for life on other planets using markers called biosignatures. The color of a planet’s surface can be one such biosignature. To see it, astronomers use a technique called reflected light spectroscopy.
But “this type of observation cannot be done with the types of telescopes that we have available today,” says Edward Schwieterman, an astronomer at the University of California Riverside who was not involved with the study. For instance, the James Webb Space Telescope can only detect biosignatures in an exoplanet’s atmosphere, like whether it has oxygen, methane, or other gases. It’s unable to measure the reflected light from the planet’s surface.