Rocket launches powering the satellite megaconstellation boom are pumping soot into the upper atmosphere at an accelerating rate, and a new UCL study warns the pollution is accumulating far faster than regulations can keep pace — with potential consequences for Earth’s climate and ozone layer.
Every time a rocket lifts a batch of internet satellites into low Earth orbit, it leaves behind something invisible but lasting: a plume of soot injected directly into the upper atmosphere, where it can linger for years and alter how much sunlight reaches Earth’s surface. A new peer-reviewed study from University College London researchers finds that this largely unregulated pollution is building up at a pace that should alarm policymakers and the public alike.
The study, published May 14 in the journal Earth’s Future, examined air pollution generated by rocket launches and the re-entry of discarded rocket bodies and defunct satellites between 2020 and 2022. Researchers then projected those emissions forward to the end of the decade. Their central finding: the rise of so-called “megaconstellation” satellite networks — systems made up of hundreds or thousands of satellites in low Earth orbit — is driving an exponential surge in launches that is rapidly reshaping the chemistry of the upper atmosphere.
What Are Megaconstellations, and Why Do They Matter?
SpaceX’s Starlink internet system is the most prominent example of a megaconstellation, with nearly 12,000 satellites currently in orbit. Amazon is developing its own rival network, known as Leo, and China is building the Guowang constellation. Together, these systems have sparked a near-tripling of annual rocket launches globally — from 114 in 2020 to 329 in 2025 — with the vast majority driven by SpaceX’s Falcon 9 rockets, which burn kerosene-based fuel.
That fuel choice matters. Kerosene combustion produces black carbon, or soot, which is released high in the atmosphere during launch. Unlike soot from cars, power plants or wildfires — which rainfall and weather systems flush out of the lower atmosphere relatively quickly — soot in the upper atmosphere has nowhere to go. Slow circulation patterns mean it can remain aloft for years, giving it roughly 540 times the climate impact of the same amount of soot emitted at ground level.
The Numbers Behind the Concern
The UCL team calculated that by 2029, the global space industry will release approximately 870 tonnes of soot into the upper atmosphere annually. To put that in perspective, the researchers note it is comparable to the total soot emitted by every passenger car in the UK — about 728 tonnes per year according to the latest government figures.
In 2020, megaconstellation missions accounted for roughly 35% of the total climate impact from the space sector. By 2029, that share is projected to climb to 42%. The accumulating pollution is expected to reduce the amount of sunlight reaching Earth’s surface to a degree the researchers compare to proposed solar geoengineering techniques — deliberate interventions designed to cool the planet by blocking incoming radiation.
“The space industry pollution is like a small-scale, unregulated geoengineering experiment that could have many unintended and serious environmental consequences. Currently the impact on the atmosphere is small, so we still have the chance to act early before it becomes a more serious issue that is harder to reverse or repair. So far there has been limited effort to effectively regulate this type of pollution,” project lead Eloise Marais, a professor of atmospheric chemistry and air quality in the Department of Geography at UCL, said in a news release.
Notably, the cooling effect from reduced sunlight is real but not necessarily welcome. While it might seem counterintuitive to worry about something that could slightly offset rising global temperatures, the researchers caution strongly against viewing this as a silver lining.
“The cooling effect from the reduction in sunlight that we calculate with our models may sound like a welcome change against the backdrop of global warming, but we need to be extremely cautious,” Marais added.
Ozone Depletion: A Secondary Threat
Beyond climate forcing, the UCL team also modeled the impact of megaconstellation launches on Earth’s ozone layer — the atmospheric shield that protects living organisms from harmful ultraviolet radiation. Rocket launches can release chlorine compounds that chemically erode ozone, and both launches and re-entries generate tiny particles that accelerate ozone-depleting reactions.
For now, the ozone threat from megaconstellations remains relatively contained. Kerosene-fueled rockets like the Falcon 9 do not emit chlorine, and the study projects that all rocket launches combined will deplete global ozone by only 0.02% by 2029 — a small fraction of the 2% attributed to substances regulated under the Montreal Protocol. But that calculus could shift. Amazon’s Leo constellation will rely partly on launch providers that use chlorine-containing solid rockets, and China’s launch vehicle choices remain unclear, though the country has historically used solid rockets that do produce chlorine.
Why the Problem Could Be Worse Than Projected
The researchers are candid that their estimates are likely conservative. Their projections were grounded in launch data from 2020 to 2022 — but the actual pace of launches between 2023 and 2025 has already outstripped those forecasts. Previous industry estimates projected 65,000 new satellites by the end of the decade; the authors note even those figures are now considered too modest.
“Rocket launches are a unique source of pollution, injecting harmful chemicals directly into the upper layers of the atmosphere and contaminating Earth’s last remaining relatively pristine environment. Though this soot’s impact on climate is currently much smaller than other industrial sources, its potency means we need to act before it causes irreparable harm,” added lead author Connor Barker, a research fellow in atmospheric chemistry/physical geography at UCL.
Why This Matters for Students and Young People
For college students who have grown up with satellite-powered GPS, streaming, and increasingly satellite broadband, this research offers an important reality check. The infrastructure enabling modern connectivity comes with environmental costs that extend far beyond carbon dioxide at ground level. The upper atmosphere — long considered beyond the reach of human pollution — is now being reshaped by an industry operating largely outside the environmental frameworks that govern emissions on Earth.
The study’s authors argue that there is still a window to act. Switching to cleaner rocket fuels, developing regulatory frameworks for upper-atmospheric emissions, and designing satellite systems for longer operational lifetimes could all reduce the sector’s footprint. But that window will not remain open indefinitely as launch cadences continue to accelerate.
Source: University College London