The satellite industry has a bold vision for the future: hundreds of thousands, maybe millions, of spacecraft circling Earth, beaming internet to remote communities, running orbital data centers, harvesting solar power. It is an ambitious picture. It is also, according to atmospheric researchers, quietly running an uncontrolled experiment on the planet's climate.
A new study published May 13 in the journal Earth's Future finds that the rapid growth of satellite megaconstellations is pumping significant amounts of pollutants into the upper atmosphere, and that without action, this pollution will eventually be enough to alter Earth's climate. The researchers describe what is already happening as "a small-scale, unregulated geoengineering experiment that could have many unintended and serious environmental consequences" — the words of Eloise Marais, a professor of atmospheric chemistry and air quality at University College London who led the research team.
The problem is not just that rockets produce exhaust. It is where that exhaust ends up. Most megaconstellation launches today depend on SpaceX's Falcon 9 rocket, which burns kerosine fuel and releases black carbon — soot — into the upper layers of the atmosphere. Unlike pollution from cars, ships, or power plants, which gets scrubbed out of the lower atmosphere relatively quickly, black carbon released at high altitude lingers for two and a half to three years. Marais notes that this makes it roughly 540 times more potent as a climate forcer than the same soot released at ground level. The upper atmosphere is, in this respect, a place where pollution goes to accumulate.
Satellite re-entries add a separate concern. When a satellite burns up on its way back into the atmosphere, it releases aluminum oxides, which have the potential to damage the ozone layer. Launches heat; re-entries corrode. Megaconstellations do both at scale and on an accelerating schedule, because the satellites themselves are designed with short operational lifespans — typically around five years — and get swapped out regularly for newer models. That churn means more rockets going up and more hardware coming down, year after year.
The numbers behind all of this are striking. Since 2020, when the megaconstellation era began in earnest, concentrations of high-altitude air pollution from the space sector have risen significantly, according to the research. On conservative estimates — and the team emphasizes conservative, since actual satellite deployment has consistently outpaced their projections — the global space industry will have released more climate-altering chemicals into the atmosphere by 2030 than the United Kingdom produces in a year. By 2029, pollution specifically from megaconstellation launches is projected to account for more than 40 percent of all space-sector air pollution.
The megaconstellation players driving this growth include SpaceX's Starlink, Amazon's LEO network, and Chinese operators Guowang and Qianfan. Starlink alone now counts more than 10,000 active satellites. The European Space Agency puts the total number of operational satellites currently in orbit above 15,000 — three times the figure from 2020. By 2030, that number could reach 100,000, with continued steep growth expected afterward.
To be clear, the researchers are not saying the sky is falling today. By 2029, the accumulated pollutants will represent roughly one hundredth of the quantity that would be needed to produce meaningful geoengineering effects. But the trajectory matters. Geoengineering — in particular, the concept of Stratospheric Aerosol Injection, which involves deliberately seeding the stratosphere with reflective particles to reduce incoming heat — is already understood to carry serious unpredictable risks: disrupted rain patterns, droughts, unforeseen weather changes. The concern Marais raises is that the space industry is inadvertently drifting toward similar territory, without the careful study, the international deliberation, or the regulatory guardrails that any intentional intervention would require.
The modeling her team uses is able to track both climate effects and ozone depletion from projected pollution loads, giving a reasonably clear picture of where the trend leads. What it cannot do is keep pace with the speed of deployment. The satellite industry is simply moving faster than the science can follow, which is itself part of the problem Marais is trying to highlight.
"We need to be taking it far more seriously in terms of regulating the pollution that's coming from launches and reentries," she told Space.com. "There also needs to be far more funding funneled into research to study this because we can't keep up with the space industry."
That gap between industrial momentum and scientific oversight is the crux of the issue. The companies building these constellations are working within existing launch regulations, which were not designed with high-volume, high-frequency megaconstellation operations in mind. Nobody sat down and decided to run an atmospheric experiment. It is an emergent consequence of thousands of individual launch decisions, each one unremarkable on its own, adding up to something researchers now feel compelled to name and study before it becomes much harder to reverse.