Low-Earth orbit, a layer of superhighway that wraps around Earth’s thermosphere some 200 to 600 miles above our heads, is newly congested.

Yet no one knows how the vast increase in satellites orbiting Earth will affect the atmosphere, and therefore life down below. With the rush to send up more and more satellites, a new study proposes that the hole in the ozone layer, a problem scientists thought they had solved decades ago, could make a comeback.

“Up until a few years ago, this was not a research area at all,” Martin Ross, an atmospheric scientist at Aerospace Corporation, said of the study, which looked at how a potential increase in man-made metal particles could eat away at Earth’s protective layer.