As Starlink deorbits hundreds of satellites, scientists warn of atmospheric pollution and regulators seek exemptions
SpaceX deorbited more than 260 Starlink satellites in the past six months, sending roughly 318 metric tons (350 tons) of spacecraft incinerating through Earth’s upper atmosphere at a rate of one to two satellites per day. As the pace of satellite reentries accelerates, a growing body of research is raising concerns about the environmental toll of deliberately burning orbital hardware in the stratosphere, even as U.S. regulators move to exempt satellite operators from environmental review.
The figure, reported by Tom’s Hardware, covers December 2025 through May 2026. Other outlets, including PCMag, have put the number closer to 472 over the same period, depending on counting methodology. Either way, the trend is clear. Harvard-Smithsonian astrophysicist Jonathan McDowell, who tracks satellite activity, told EarthSky and The Register that one to two Starlink satellites now reenter the atmosphere every day, and that rate is expected to climb to as many as five per day as the constellation grows.
SpaceX currently operates roughly 8,000 Starlink satellites in low Earth orbit, with more than 10,000 launched to date. Each second-generation Starlink satellite weighs approximately 1,225 kilograms (2,700 pounds) at launch. Over a five-year operational life span, every satellite is intentionally deorbited to burn up in the atmosphere, a practice the company frames as a responsible approach to space debris mitigation.
A growing chemical footprint
The concern is not that satellites are coming down. It is what happens when they do.
When a spacecraft reenters the atmosphere at orbital velocity, friction heats it to thousands of degrees, vaporizing the structure into a fine mist of metallic particles and reactive gases. Aluminum, which makes up roughly 30% of a typical satellite’s mass, oxidizes on contact with atmospheric oxygen, forming aluminum oxide nanoparticles.
According to a 2024 study in Geophysical Research Letters, these nanoparticles act as catalysts in the stratosphere, providing surfaces on which chlorine compounds can convert into ozone-destroying forms. Even a 2% reaction probability on aluminum oxide surfaces is enough to accelerate ozone depletion, the researchers found.
The U.S. National Oceanic and Atmospheric Administration has reported that roughly 10% of aerosol particles in the stratosphere already contain aluminum and exotic metals from satellite and rocket reentries. NOAA projects that figure could reach 50% as space traffic increases.
A 2025 NOAA study in the Journal of Geophysical Research modeled what 10 gigagrams (11,000 tons) per year of aluminum oxide emissions would do to the middle and upper atmosphere, a level consistent with projected megaconstellation growth by 2040. The results showed statistically significant changes: 1.5-degree Celsius (2.7-degree Fahrenheit) temperature anomalies in the mesosphere and stratosphere, accompanied by a 10% reduction in wind speed in the Southern Hemisphere polar vortex. The study found some scenarios also strengthened the Northern Hemisphere polar vortex while weakening the springtime ozone hole recovery.
First direct measurements
In February 2026, researchers at the Leibniz Institute for Atmospheric Physics published the first direct measurement of metal pollution from a reentering spacecraft. The study, led by Robin Wing in Communications Earth & Environment, tied a lithium plume detected over Germany to the uncontrolled reentry of a Falcon 9 upper stage that had failed to execute its deorbit burn. A Falcon 9 upper stage carries roughly 30 kilograms (66 pounds) of lithium in its aluminum-lithium alloy hull and batteries. Meteorites, by comparison, deposit only about 80 grams (2.8 ounces) of lithium into the atmosphere each day.
The detection confirmed what models had predicted: atmospheric reentry of human-made space hardware is measurably altering the chemical composition of the stratosphere. The question that remains unanswered, McDowell told The Register, is how significant the effects will be.
“The answers have ranged from ‘this is too small to be a problem’ to ‘we’re already screwed,'” he said. “But the uncertainty is large enough that there’s already a possibility we are damaging the upper atmosphere.”
FCC moves to exempt satellites from environmental review
Against this backdrop, the Federal Communications Commission has proposed excluding satellite operations entirely from review under the National Environmental Policy Act (NEPA). The August 2025 rulemaking, championed by FCC Chairman Brendan Carr, argues that satellite activities are “extraterritorial” with effects “located entirely outside of the jurisdiction of the United States.”
The proposal would broaden a 1986 categorical exclusion that already exempts satellite reentries from environmental review. The Government Accountability Office criticized the FCC in 2022 for failing to reconsider that exclusion in light of the massive growth of satellite constellations.
A coalition of satellite operators including SpaceX, Amazon’s Project Kuiper, AST SpaceMobile, Iridium, SES, Globalstar, and Telesat filed comments supporting the exemption. The industry argument is that the FCC’s NEPA process has become a major obstacle to infrastructure deployment.
Opposing the exemption are the American Astronomical Society, a coalition of 17 state attorneys general and the District of Columbia, tribal governments, and state historic preservation officers. The AAS warned the FCC that satellite reentries “can deposit metal vapor into the atmosphere with potential climate and air quality effects.” The state AGs argued the FCC cannot ignore the environmental consequences of launch emissions, reentry debris, light pollution, and orbital congestion, and they flagged a procedural violation: the FCC’s notice contained only broad questions without draft rule text, a potential violation of the Administrative Procedure Act.
The comment period closed in October 2025. A final order is expected in 2026.
What comes next
SpaceX is simultaneously accelerating its deorbit operations and planning to lower the orbital altitude of roughly 4,400 Starlink satellites from 550 kilometers (342 miles) to 480 kilometers (298 miles) over the course of 2026, a move the company says will reduce the ballistic decay time of failed satellites from more than four years to just months. The lower orbit increases safety from a debris perspective, but it also means more satellites will be reentering more frequently.
If SpaceX reaches its planned constellation size of 42,000 satellites, and if competitors such as Amazon Kuiper, OneWeb, and China’s Spacesail Qianfan deploy their own megaconstellations, the daily reentry rate could climb far beyond five per day. Researchers estimate that maintaining a fully deployed second-generation Starlink constellation would require replacing satellites at a rate of dozens per day, year after year, depositing more than 8,000 metric tons (8,800 tons) of metals into the upper atmosphere annually.
That would far exceed the natural meteoritic influx, and it would introduce elements such as aluminum, lithium, copper, and titanium that are not abundant in natural cosmic dust. The atmospheric chemistry of those materials, at those concentrations, is not well understood.
“The uncertainty is large enough that there is already a possibility we are damaging the upper atmosphere,” McDowell said. “It is murky right now, and that scares me.”
Sources: Tom’s Hardware, PCMag, The Register, NOAA, Geophysical Research Letters, Communications Earth & Environment, Broadband Breakfast, Harvard Salata Institute, AAS, FCC