The race to fill low Earth orbit with vast fleets of satellites is raising alarms among atmospheric scientists, who warn that the mass burning of defunct spacecraft could damage the ozone layer and alter Earth's climate in ways that remain poorly understood. With SpaceX seeking permission to launch up to one million satellites and more than 1.23 million spacecraft now proposed worldwide, researchers and policymakers are calling for global regulation before the atmospheric consequences become irreversible.
An Atmosphere Turned 'Crematorium'
In a paper published this week in The Conversation, atmospheric chemist Laura Revell of the University of Canterbury, planetary astronomer Michele Bannister of the same institution, and astronomer Samantha Lawler of the University of Regina described the growing practice of deliberately burning up retired satellites as turning the atmosphere into "a crematorium for satellites". The authors estimated that a constellation of one million satellites could deposit a teragram — one billion kilograms — of alumina in the upper atmosphere, "enough, alongside launch emissions, to significantly alter atmospheric chemistry and heating in dramatic ways we do not yet understand".
Their warning comes weeks after SpaceX filed an application with the U.S. Federal Communications Commission on January 30 for a constellation of up to one million satellites intended to serve as orbital data centers for artificial intelligence. The proposal dwarfs the roughly 14,000 active satellites currently in orbit. Blue Origin announced its own 5,408-satellite TeraWave constellation on January 21, and China's Qianfan and Guowang programs are also advancing.
The Science of Satellite Pollution:
When satellites reenter the atmosphere, their aluminum structures burn and generate aluminum oxide nanoparticles. A 2024 study by University of Southern California researchers, published in Geophysical Research Letters, found that a single 250-kilogram satellite produces about 30 kilograms of aluminum oxide during reentry. In 2022, reentering satellites released an estimated 17 metric tons of these particles. If planned mega-constellations reach full deployment, that figure could exceed 360 metric tons annually — a 646 percent increase over natural levels.
Unlike chlorofluorocarbons, aluminum oxides are not consumed in the chemical reactions that destroy ozone; they act as catalysts, enabling ozone-depleting reactions to continue for decades. A separate 2025 study by CIRES and NOAA researchers found that by 2040, enough alumina could accumulate to heat parts of the mesosphere by as much as 1.5 degrees Celsius and reduce polar vortex wind speeds by about 10 percent. "We're really changing the composition of the stratosphere into a state that we've never seen before," said John Dykema, an applied physicist at Harvard.
A Regulatory Gap:
Despite the mounting evidence, the FCC is not required to conduct environmental reviews for satellite constellation licenses, relying on a categorical exclusion under the National Environmental Policy Act that has been in place since 1986. A 2022 Government Accountability Office report found the FCC had never assessed whether that exclusion remains appropriate for constellations of tens of thousands of satellites, and recommended the agency reconsider. Lawler and her co-authors argue that "there is no public mandate for a single company in one country to make changes on that scale to the planet's atmosphere," and are calling for a defined safe atmospheric carrying capacity for satellite launches and reentries before the industry scales further.
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