A global push fixed the ozone hole. Satellites can threaten it.

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

However, no one knows how the large increase in satellites orbiting the Earth will affect the atmosphere and therefore life 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, may be back.

“Until a few years ago, this was not a research area at all,” Martin Ross, an atmospheric scientist at the Aerospace Corporation, said of the study, which looked at how a potential increase in man-made metal particles could wreak havoc. The protective layer of the earth.

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 evaporation has little impact. But the new satellites — much more advanced but also smaller, cheaper and more readily available than previous satellites — have a circulation that resembles fast fashion, said the study’s lead author, José Pedro Ferreira, a Ph.D. for a doctorate 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 past half-decade, burning up in super-fast, super-hot flames.

Mr. Ferreira calculated that upon satellite reentry, much of a burned-up satellite could become aluminum oxide, a pollutant that can interfere with the chemistry of stratospheric ozone. 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 lead to in considerable ozone. exhaustion.

“We’re still at the beginning of a big research effort, so it’s too early to be sure there’s a negative impact, but we’re clearly starting to see pieces of the 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 anti-satellite, but added to a growing body of research on sustainable space development.

Daniel Cziczo, a professor of earth, atmospheric and planetary sciences at Purdue University, flies high-altitude aircraft to look at particles left in the atmosphere by meteoroids. Last year, he published a study that showed these particles were being coagulated with man-made metals from satellites.

He said Mr Ferreira’s study jumped to conclusions not supported by his own research, applying the wrong size, composition and chemistry to particles that exist in the atmosphere.

The increased number of launches and the dismantling of more satellites that mostly burn up means there will be more material in the atmosphere, said Dr. Cziczo. “It raises the question of what impact that will have, and we don’t know that yet.” He said that ozone depletion and the climate effects of satellites should be studied, but he did not think that this document was approaching these issues correctly.

Mr Ferreira said “models are only as good as the data you have to validate them with, so we have to be careful and careful about the level of certainty we have about environmental impacts”.

Regulators are slowly coming to grips with the unanswered questions that come with the growth of 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 array 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 the Aerospace Corporation. But the regulatory body could step in over the next few years.

“This is something that the world needs to take really seriously, and the Montreal Protocol is aware of and will study this,” said David Fahey, co-chair of the Montreal Protocol’s Scientific Assessment Panel and director of the Chemical Sciences Laboratory at National. Oceanic and Atmospheric Administration.

The protocol, he said, will consider the matter for their next assessment to be completed in 2026.