Rocket emissions and re-entry pollution threaten to delay ozone restoration, however coordinated motion and cleaner propulsion may forestall long-term injury.
The sharp improve in world rocket launches could hinder the restoration of the ozone layer, warns Sandro Vattioni. Though the danger is being underestimated, he notes that it may very well be decreased by way of proactive and coordinated measures.
Lately, the enlargement of satellite tv for pc constellations in low Earth orbit has reworked the evening sky, fueled by the speedy progress of the house 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 protect towards dangerous ultraviolet radiation. Scientists are solely starting to completely assess the size 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 influence was thought of 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 speedy progress.
An extended-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 occasions longer, since elimination processes resembling precipitation don’t happen at these altitudes. Whereas most launches happen within the Northern Hemisphere, atmospheric circulation finally distributes the pollution globally.
To research 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 influence the ozone layer by 2030.
In a high-growth situation with 2,040 annual launches by 2030 — roughly eight occasions the 2024 whole — the mannequin predicts that world common ozone thickness would lower by almost 0.3%. Seasonal losses may 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 underneath the 1989 Montreal Protocol. Even at present, world ozone thickness stays about 2% beneath pre-industrial ranges, and full restoration will not be anticipated till round 2066. The examine means that unchecked rocket emissions — which at the moment stay unregulated — may push this timeline again by a number of years and even many years, relying on how rapidly the house 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 strong rocket motors. At present, the one propulsion methods which have a negligible impact on the ozone layer are these which use cryogenic fuels resembling liquid oxygen and hydrogen. Nevertheless, as a result of technological complexity of dealing with cryogenic fuels, solely about 6% of rocket launches at the moment use this know-how.
Re-entry results are nonetheless unsure
We wish to point out that our examine solely thought of emissions launched from rockets throughout ascent into house. 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 extra pollution, together with numerous steel particles and nitrogen oxides, as a result of 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 might intensify ozone loss.
These re-entry results are nonetheless poorly understood and never but integrated into most atmospheric fashions. From our perspective, it’s clear that with growing satellite tv for pc constellations, re-entry emissions will grow to be extra frequent, and the full influence on the ozone layer is more likely to be even larger than present estimates. Science known as upon to fill these gaps in our understanding.
Wanted: Foresight and coordinated motion
However that alone is not going to be sufficient. The excellent news: We imagine a launch trade that avoids ozone-damaging results is fully potential: Monitoring rocket emissions, minimizing the utilization of chlorine and soot-producing fuels, selling various propulsion methods, and implementing the mandatory and acceptable laws are all key to making sure that the ozone layer continues its restoration. This may take coordinated efforts between scientists, policymakers, and trade.
The Montreal Protocol efficiently demonstrated that even planetary-scale environmental threats will be addressed by way of world cooperation. As we enter a brand new period of house exercise, the identical type of foresight and worldwide coordination will likely 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 may gradual 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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