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.
Ever since Sputnik, the first man-made space satellite, was launched in 1957, scientists have thought that when satellites re-enter our atmosphere at the end of their lives, their vaporization has little impact. But new satellites — much more advanced, but also smaller, cheaper and more disposable than previous satellites — have a turnover that resembles fast fashion, said the lead author of the study, José Pedro Ferreira, a doctoral candidate in astronautical engineering at the University of Southern California.
Almost 20 percent of all satellites ever launched have re-entered Earth’s atmosphere in the last half-decade, burning up in superfast, superhot blazes.
Mr. Ferreira calculated that upon satellite re-entry, the bulk of a burned-up satellite could become aluminum oxide, a pollutant that could interfere with stratospheric ozone chemistry. Each satellite can generate just under 70 pounds of aluminum oxide nanoparticles.
The study, which relied on laboratory measurements and computer models, posits that if the number of satellites launched results in mega-constellations of hundreds or thousands, they could create an excess of aluminum 640 percent above natural levels, which could potentially lead to significant ozone depletion.
“We’re still in the very beginning of a big research effort, so it’s too early to be sure that there is a negative impact, but we’re clearly starting to see the pieces of evidence,” said Mr. Ferreira, whose research, published in Geophysical Research Letters, was funded by NASA and the National Science Foundation.
Mr. Ferreira said studies like his were not antisatellite, but added to a growing body of research on the sustainable development of space.
Daniel Cziczo, a professor of earth, atmospheric and planetary sciences at Purdue University, flies high-altitude aircraft to look at the particles left in the atmosphere from meteoroids. Last year, he published a study that showed these particles were coagulating with man-made metals from satellites.
He said Mr. Ferreira’s study jumped to conclusions not supported by his own research by applying the incorrect size, composition and chemistry to the particles that exist in the atmosphere.
Increasing the number of launches, and decommissioning more satellites that largely burn up, means there’s going to be more material in the atmosphere, Dr. Cziczo said. “It brings up the question of what impact will that have, and we don’t know that yet.” He said ozone depletion and the climate effects of satellites needed to be studied, but he did not think this paper was approaching those issues correctly.
Mr. Ferreira said “models are only as good as the data you have to validate it with, so we should be cautious and careful about the level of certainty we have concerning environmental impacts.”
Regulators are slowly taking note of the unanswered questions that come with increasing space hardware. In 2019, the United Nations Committee on the Peaceful Uses of Outer Space published long-term sustainability guidelines that recommended regulating the environmental effects of space activities on the planet. In 2022, the Federal Communications Commission, which licenses most satellites, approved 7,500 of SpaceX’s requested batch of nearly 30,000 satellites.
The Montreal Protocol, an international agreement that regulated ozone-depleting substances in 1987, was written to cover gases, not particles, according to Dr. Ross of Aerospace Corporation. But the regulatory body could step in over the coming years.
“This is something the world should really take seriously, and the Montreal Protocol is aware and will be studying this,” said David Fahey, co-chair of the Scientific Assessment Panel of the Montreal Protocol and director of the Chemical Sciences Laboratory at the National Oceanic and Atmospheric Administration.
The Protocol, he said, would look into the issue for their next assessment to be completed in 2026.