For astronomers seeking Earth twins around other stars, the exoplanet GJ 1132 b probably isn’t an identical sibling—but it may be the closest cousin yet found. It weighs in at just over one Earth mass, but circles its star in a warm orbit that could make it more like Venus than our own world. Moreover, its diameter is nearly 50 percent larger than that of Earth, suggesting it possesses a thick atmosphere. Now, after taking the closest-ever look at GJ 1132 b, a European collaboration has confirmed the presence of its atmosphere and found hints it might contain water and methane. The results are currently under review for publication in The Astrophysical Journal.

As mere discoveries of exoplanets become routine, efforts to learn more about them—their compositions, climates and histories—are moving to the fore, with studies of their atmospheres occupying center stage. Although astronomers detected the first exoplanet atmosphere more than 15 years ago, they have only managed to observe a handful ever since, mostly for very hot worlds as big as Jupiter or even larger. With their first glimpse of GJ 1132 b’s alien air, astronomers are now entering a new frontier as they examine the atmospheres of smaller, more Earth-like worlds.