Rocket emissions and back -to -school pollutants threaten to delay ozone recovery, but coordinated action and cleaner propulsion could prevent long -term damage.
The net increase in global rocket launches can hinder the recovery of the ozone layer, warns Sandro Vattioni. Although the risk is underestimated, he notes that it could be reduced by proactive and coordinated measures.
In recent years, the expansion of satellite constellations into low terrestrial orbit has transformed the night sky, fueled by the rapid growth of the space industry. This progress creates major opportunities but also raises environmental challenges. Pollutants released during rocket launches and burning debris during the start of the school year accumulate in the average atmosphere, where they can damage the ozone layer – the earth shield against harmful ultraviolet radiation. Scientists are only starting to fully assess the magnitude of this threat.
The surveys on how rocket emissions affect ozone began more than three decades ago, but for many years, the impact was considered minimal. While the frequency of launches continues to increase, this view changes. In 2019, only 97 orbital launches were recorded worldwide, but in 2024, the figure had climbed to 258, with projections pointing towards rapid growth.
A long-term concern for a long time
Unlike pollutants at ground level, the emissions of rockets and satellites that come in can persist in the average and upper atmosphere up to 100 times more, because the elimination processes such as precipitation does not occur at these altitudes. While most launches take place in the northern hemisphere, atmospheric circulation ultimately distributes pollutants worldwide.
To study the long-term effects, researchers from ETH Zurich and the physical meteorological observatory in Davos (PMOD / WRC), in collaboration with the international team of Laura Revell at the University of Canterbury, used a model of chemistry-climatization to simulate how future emissions could have an impact on the ozone layer by 2030.
In a strong growth scenario with 2,040 annual launches by 2030 – approximately eight times the total 2024 – the model predicts that the global ozone thickness decreases by almost 0.3%. Seasonal losses could reach up to 4% on Antarctica, where the ozone hole continues to reappear each spring.
Although these reductions may seem weak, the context is critical. The ozone layer is always recovering from an earlier depletion caused by long -lived chlorofluorocarbons (CFC), which have been prohibited in the 1989 Montreal protocol. Even today, the world thickness of ozone remains around 2% below pre -industrial levels, and complete recovery is not expected before 2066. Uncontrolled rockets – which are currently unregulated – could repel this chronology of several years, even decades, depending on the speed with which the space industry develops.
With rockets too, the choice of fuel counts
The main contributors to the exhaustion of ozone rocket emissions are gaseous chlorine and soot particles. Chlorine catalystly destroys ozone molecules, while soot particles warm the average atmosphere, accelerating chemical reactions impoverishing ozone.
While most of the rocket propellants emit soot, chlorine emissions come mainly from solid rocket engines. Currently, the only propulsion systems that have a negligible effect on the ozone layer are those that use cryogenic fuels such as liquid oxygen and hydrogen. However, due to the technological complexity of the handling of cryogenic fuel, only about 6% of rocket launches are currently using this technology.
Back to school effects are still uncertain
We would like to mention that our study considered only the releases released from the rockets during the ascent in space. But this is only part of the image. Most satellites in low terrestrial orbit enter the atmosphere at the end of their operational life, burning in the process.
This process generates additional pollutants, including various metallic particles and nitrogen oxides, due to the intense heat generated during the start of the school year. Although nitrogen oxides are known to exhaust catalystly ozone, metallic particles can help form polar stratospheric clouds or serve as reaction surfaces themselves, which can both intensify the loss of ozone.
These return to school effects are still poorly understood and not yet incorporated into most atmospheric models. From our point of view, it is clear that with the increase in the constellations of satellites, the start -up emissions will become more frequent and the total impact on the ozone layer is probably even higher than current estimates. Science is called upon to fill these shortcomings in our understanding.
Necessary: Provident and coordinated action
But that alone will not be enough. The good news: we believe that a launch industry that avoids the effects damaging ozone is quite possible: monitoring rocket emissions, minimizing the use of chlorine and fuel producing soot, promoting alternative propulsion systems, and the implementation of the necessary and appropriate regulations is all essential to guarantee that the ozone layer continued its recovery. This will take coordinated efforts between scientists, decision -makers and industry.
The Montreal Protocol has successfully demonstrated that even environmental threats on a planetary scale can be treated by global cooperation. While we are entering a new era of spatial activity, the same type of foresight and international coordination will be necessary to avoid the harmful effects on the ozone layer – one of the most vital natural shields of the earth.
Reference: “The launches of close rockets could slow down the recovery of ozone” by Laura E. Revell, Michele T. Bannister, Tyler FM Brown, Timofei Sukhodolov, Sandro Vattioni, John Dykema, David J. Frame, John Cater, Gabriel Chiodo and Eugene Rozanov, June 9, 2025 NPJ climate and atmospheric science.
Two: 10.1038 / S41612-025-01098-6
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