LOS ANGELES, July 7 — The scene unfolding above our heads is invisible to the naked eye, but scientists say the chemical fallout from thousands of vaporizing satellites could be rewriting the timetable for ozone layer recovery. Every time a spent satellite plummets back to Earth and burns up in the atmosphere, it leaves behind a fine metallic dust. A 2023 study in the journal Geophysical Research Letters calculated that a single Starlink satellite’s reentry can generate up to 30 kilograms — 66 pounds — of aluminum oxide nanoparticles.
Those particles, the researchers found, do not simply vanish. They linger in the stratosphere for years, and aluminum oxide is a known catalyst for the very chemical reactions that destroy ozone.
The math is troubling. Over a recent six-month period, SpaceX deorbited 260 satellites. Those 260 units represented a total mass of 702,000 pounds of hardware.
But that is just the beginning. With plans for satellite constellations numbering in the tens of thousands, researchers warn the annual mass of vaporized metal entering the upper atmosphere could reach millions of pounds.
A treaty gap The Montreal Protocol of 1987 is widely celebrated as one of the most successful environmental treaties in history. It phased out chlorofluorocarbons, or CFCs, the chemicals that punched a hole in the ozone layer. That hole has been slowly healing.
But satellite reentry emissions are not regulated under that treaty. The stratosphere, where the ozone layer resides, is particularly sensitive to chemical changes. Introduce a catalyst like aluminum oxide, and the reactions that break apart ozone molecules accelerate.
The Geophysical Research Letters study warned that if the current pace of satellite launches and deorbits continues unchecked, the cumulative effect could delay the ozone layer’s full recovery by up to a decade. Other pollutants are coming along for the ride.
Satellites are packed with batteries, wiring, and electronics that contain copper, lithium, and other metals. When those components incinerate during reentry, they too become nanoparticles that drift through the upper atmosphere. Calls for research The National Oceanic and Atmospheric Administration — NOAA — has publicly called for more research into the atmospheric effects of satellite reentry.
The numbers are still small compared to the CFC crisis of the 1980s. But the trajectory is steep.
Today’s constellations number in the thousands. Tomorrow’s could number in the hundreds of thousands. Every one of those satellites will eventually need to come down.
