A monstrous cloud of accumulated methane—a potent greenhouse gas—is now hovering over a large portion of the western United States according to satellite imagery analyzed by NASA and reported by the Washington Post.

Created by years of intentionally released and errantly leaked natural gas during fossil fuel drilling operations, the cloud—invisible to the human eye but captured by advanced satellite imaging technology—is centered over northwest New Mexico and described by the Post as “a permanent, Delaware-sized methane cloud, so vast that scientists questioned their own data when they first studied it three years ago.”

So alarmed by the size of the plume were scientists, NASA researcher Christian Frankenberg told the Post, “We couldn’t be sure that the signal was real.”

Though there is considerably less of it put into the atmosphere each year, methane is twenty times more powerful as a greenhouse gas than carbon-dioxide or CO2.