Rocket emissions and re-entry pollution threaten to delay ozone restoration, however coordinated motion and cleaner propulsion might stop long-term injury.
The sharp enhance in international rocket launches could hinder the restoration of the ozone layer, warns Sandro Vattioni. Though the danger is being underestimated, he notes that it might be decreased by way of proactive and coordinated measures.
Lately, the enlargement of satellite tv for pc constellations in low Earth orbit has remodeled the night time sky, fueled by the fast progress of the area trade. This progress creates main alternatives but in addition raises environmental challenges. Pollution launched throughout rocket launches and from burning particles throughout re-entry accumulate within the center ambiance, the place they will injury the ozone layer — Earth’s defend in opposition to dangerous ultraviolet radiation. Scientists are solely starting to totally assess the dimensions of this menace.
Investigations into how rocket emissions have an effect on ozone started greater than three many years in the past, however for a few years the affect was thought-about minimal. Because the frequency of launches continues to rise, this view is shifting. In 2019, solely 97 orbital launches had been recorded worldwide, however by 2024 the determine had climbed to 258, with projections pointing to continued fast progress.
A protracted-underestimated concern
Not like ground-level pollution, emissions from rockets and re-entering satellites can persist within the center and higher ambiance as much as 100 instances longer, since elimination processes similar to precipitation don’t happen at these altitudes. Whereas most launches happen within the Northern Hemisphere, atmospheric circulation ultimately distributes the pollution globally.
To analyze long-term results, researchers from ETH Zurich and the Bodily Meteorological Observatory in Davos (PMOD/WRC), in collaboration with Laura Revell’s worldwide staff on the College of Canterbury, used a chemistry–local weather mannequin to simulate how future emissions would possibly affect the ozone layer by 2030.
In a high-growth situation with 2,040 annual launches by 2030 — roughly eight instances the 2024 complete — the mannequin predicts that international common ozone thickness would lower by practically 0.3%. Seasonal losses might attain as a lot as 4% over Antarctica, the place the ozone gap continues to reappear every spring.
Whereas these reductions could seem small, the context is important. The ozone layer continues to be recovering from earlier depletion brought on by long-lived chlorofluorocarbons (CFCs), which had been banned below the 1989 Montreal Protocol. Even immediately, international ozone thickness stays about 2% under pre-industrial ranges, and full restoration just isn’t anticipated till round 2066. The examine means that unchecked rocket emissions — which at present stay unregulated — might push this timeline again by a number of years and even many years, relying on how shortly the area trade expands.
With rockets, too, the selection of gasoline issues
The primary contributors to ozone depletion from rocket emissions are gaseous chlorine and soot particles. Chlorine catalytically destroys ozone molecules, whereas soot particles heat the center ambiance, accelerating ozone-depleting chemical reactions.
Whereas most rocket propellants emit soot, chlorine emissions primarily come from stable rocket motors. Presently, the one propulsion methods which have a negligible impact on the ozone layer are these which use cryogenic fuels similar to liquid oxygen and hydrogen. Nevertheless, because of the technological complexity of dealing with cryogenic fuels, solely about 6% of rocket launches at present use this know-how.
Re-entry results are nonetheless unsure
We wish to point out that our examine solely thought-about emissions launched from rockets throughout ascent into area. However that is solely a part of the image. Most satellites in low Earth orbit re-enter the ambiance on the finish of their operational life, burning up within the course of.
This course of generates further pollution, together with varied steel particles and nitrogen oxides, because of the intense warmth generated upon re-entry. Whereas nitrogen oxides are recognized to deplete ozone catalytically, steel particles could contribute to forming polar stratospheric clouds or function response surfaces themselves, each of which may intensify ozone loss.
These re-entry results are nonetheless poorly understood and never but integrated into most atmospheric fashions. From our standpoint, it’s clear that with growing satellite tv for pc constellations, re-entry emissions will change into extra frequent, and the overall affect on the ozone layer is prone to be even larger than present estimates. Science is named upon to fill these gaps in our understanding.
Wanted: Foresight and coordinated motion
However that alone won’t be sufficient. The excellent news: We imagine a launch trade that avoids ozone-damaging results is completely doable: Monitoring rocket emissions, minimizing the utilization of chlorine and soot-producing fuels, selling various propulsion methods, and implementing the mandatory and applicable laws are all key to making sure that the ozone layer continues its restoration. This can take coordinated efforts between scientists, policymakers, and trade.
The Montreal Protocol efficiently demonstrated that even planetary-scale environmental threats might be addressed by way of international cooperation. As we enter a brand new period of area exercise, the identical sort of foresight and worldwide coordination can be wanted to keep away from dangerous results on the ozone layer – one of many Earth’s most important pure shields.
Reference: “Close to-future rocket launches might sluggish ozone restoration” by Laura E. Revell, Michele T. Bannister, Tyler F. M. Brown, Timofei Sukhodolov, Sandro Vattioni, John Dykema, David J. Body, John Cater, Gabriel Chiodo and Eugene Rozanov, 9 June 2025, npj Local weather and Atmospheric Science.
DOI: 10.1038/s41612-025-01098-6
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