As the Artemis space programme looks to spark a race to the Moon there are new warnings of the rise in pollution from so-called “megaconstellation” satellite systems.

The study by a team at University College London found that the systems, launched en masse into space since 2019 will account for nearly half (42%) of the total climate impact of space sector pollution by the end of the decade,

Researchers examined air pollution produced by the growing number of rocket launches, and the discarded rocket bodies and dead satellites falling back to Earth. The black carbon (soot) generated from these sources lingers in the upper atmosphere far longer than that from ground-based sources, resulting in a 500-fold greater impact on the climate.

Using data from rocket launches and satellite deployments between 2020 and 2022, the team projected emissions out to the end of the decade. The analysis showed that in 2020 these megaconstellations contributed about 35% to the total climate impact from the space sector and will climb to 42% by 2029.

The research also found that the potent air pollution generated by the launch and re-entry of large, disposable satellite systems is rapidly accumulating in the upper atmosphere, decreasing the amount of sunlight reaching Earth’s surface. By 2029, the accumulating pollution would have an effect similar to proposed geoengineering techniques, which aim to cool the planet by blocking some sunlight with particles injected into the upper atmosphere.

Project lead, Professor Eloise Marais, UCL Geography, said: “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.”

The research indicated that not all the environmental impacts of the satellites will be negative. Soot from rocket launches has a mild cooling effect on Earth’s climate. However, this effect will be minimal compared with how much the planet’s temperature is set to rise over the same period due to global warming.

Additionally, the researchers say that their predictions are likely to be an underestimate. They based their future projections on trends over the first few years (2020 to 2022) of the satellite “megaconstellation” era, but the number of rocket launches between 2023 and 2025 has surpassed their projections and many more are expected to be launched in the coming years.

Marais added: “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.”

The research team modelled all the major pollutants from launches and re-entries of satellite megaconstellations, a new class of satellite missions made up of hundreds or thousands of satellites in low Earth orbit that have caused an exponential growth in launches and re-entries in the past few years.

SpaceX’s internet-providing Starlink system is the best known megaconstellation. With nearly 12,000 satellites in orbit so far, it is by far the largest, though rival systems have also deployed hundreds of additional satellites. The authors note that previous estimates projecting another 65,000 satellites launched by the end of the decade are already outdated and likely too conservative in light of recent filings.

The researchers found that though the era of megaconstellations only began in earnest in 2020, these missions now consume more than half of all rocket fuel and are expected to continue to grow. The industry’s zeal to deploy new and expand existing constellations has led to a near tripling of annual rocket launches from 114 in 2020 to 329 in 2025, driven predominantly by SpaceX’s Falcon 9 rockets.

Lead author Dr Connor Barker, UCL Geography, said: “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.”