Massive satellite launches are filling the upper atmosphere with soot

A team of researchers from University College London publishes this Thursday in the journal Earth’s Future, an analysis of the atmospheric pollution produced by the increasing number of launches, as well as by the bodies of discarded rockets and useless satellites that fall back to Earth.

The black carbon (or soot) generated by these objects remains in the upper atmosphere much longer than that from terrestrial sources, which translates into a 500 times greater impact on the climate, the authors emphasize.

Using data from rocket launches and satellite deployments between 2020 and 2022, the team has modeled all the main pollutants from the launches and re-entries of mega satellite constellations. In addition, they have projected the sector’s soot emissions until the end of this decade.

The analysis shows that, in 2020, these ‘megaconstellations’ contributed around 35% to the total climate impact of the space sector and that this figure will increase to 42% in 2029.

The research also reveals that powerful air pollution generated by the launch and re-entry of large expendable satellite systems is rapidly accumulating in the upper atmosphere, reducing the amount of sunlight reaching the Earth’s surface.

Curiously, the accumulated soot pollution expected in 2029 would have a similar effect to that of the geoengineering techniques proposed to cool the planet, blocking part of the sunlight with particles injected into the upper atmosphere, but the benefit will be “minimal compared to the increase in the planet’s temperature expected for that period,” the authors warn.

“Currently, the impact of these pollutants on the atmosphere is relatively small, so we still have the opportunity to act in time before it becomes a more serious problem that is difficult to reverse or repair,” says one of the authors, Eloise Marais, a geographer at University College.

The researchers warn that their predictions are likely to be an underestimate, given that the period on which they based their forward-looking forecasts (2020 to 2022) saw fewer launches than those that have taken place in subsequent years (2023 and 2025) and those that are expected to occur in the future.

SpaceX’s Starlink system (owned by billionaire Elon Musk) is the best-known megaconstellation, with nearly 12,000 satellites in orbit to date, although rival systems have also deployed hundreds of additional satellites.

The authors point out that previous estimates, which called for the launch of another 65,000 satellites by the end of the decade, are already out of date.

The industry’s eagerness to deploy new constellations and expand existing ones has led to annual rocket launches almost tripling, from 114 in 2020 to 329 in 2025.

The launches are powered primarily by SpaceX’s Falcon 9 rockets, which use kerosene-based fuel, releasing soot particles into the upper layers of the atmosphere during launch.

This soot remains in that atmospheric layer for years, unlike that from land sources, such as cars and power plants, which is eliminated with rain.

The authors emphasize that the soot released by these launches is about 540 times more effective at altering the climate than soot emitted near the Earth’s surface.

In addition, satellite launches also release chemicals such as chlorine into the atmosphere, which can degrade ozone capture, they warn.