SAN FRANCISCO, CALIFORNIA—Reliably active and accessible to tourists, Mount Yasur, a volcano on the remote Pacific archipelago of Vanuatu, has long been a local attraction. But now, it could become an international landmark: It may be the first volcano to have burped up a plume of carbon dioxide (CO2) that was measured from space. In May 2015, researchers using NASA’s Orbiting Carbon Observatory 2 (OCO-2) found Yasur to be belching CO2 into the air at a rate of 42 kilotons per day, they reported on 14 December here at the annual meeting of the American Geophysical Union. The measurements were not easy: Clouds, dust, and distance all threatened to confound the results. Moreover, unlike sulfur dioxide, a volcanic gas that stands out against trace background levels, the atmosphere contains higher background levels of CO2, and winds disperse any injection quickly. So OCO-2 scientists were never expecting to record the emissions of individual point sources, like volcanoes or coal-fired power plants. Rather, they were more interested in the seasonal wax and wane of the global carbon cycle. Yet OCO-2 happened to pass directly above Yasur when its emissions were popping, amid the surrounding pristine Pacific air. The lucky detection points the way toward viable verification of greenhouse gas emissions, which will be needed to help enforce climate treaties. It also foreshadows the space-based monitoring of the fumes that can forewarn of volcanic eruptions.