A rapid increase in the number of missile launches worldwide could slow the recovery of the ozone layer, which protects the Earth from harmful ultraviolet radiation. This problem remains underestimated, although it can be solved through thoughtful and coordinated actions.
The space industry has been booming in recent years, which led to the emergence of numerous satellite constellations in low Earth orbit. It opens up new opportunities, but at the same time creates environmental challenges. Emissions from rocket launches and the return of space debris into the atmosphere pollute the middle layers of the atmosphere, causing damage to the ozone layer.
Studies of the impact of rocket emissions on the ozone layer began over 30 years ago, but it used to be considered, that their influence is insignificant. However, with the active growth of the number of launches, the situation is changing. IN 2019 year in the world took place 97 orbital launches, in 2024 year their number increased to 258, and further rapid growth is predicted.
Long-term exposure to emissions
Emissions from rockets and space debris in the middle and upper atmosphere, that returns, can stay until 100 times longer, than emissions on the earth's surface, due to the lack of natural cleaning mechanisms, such as leaching by precipitation. Although most launches take place in the Northern Hemisphere, atmospheric circulation distributes these pollutants around the world.
An international research team involving the University of Canterbury, ETH Zurich and the Physical Meteorological Observatory in Davos (PMOD/WRC) used a climate model to predict the impact of rocket emissions on the ozone layer 2030 year. According to the scenario from 2040 launches annually - eight times more, than in 2024 year - the global thickness of the ozone layer will decrease by 0,3%, and seasonal losses over Antarctica, where an ozone hole forms every spring, can reach 4%.
Although these numbers seem small, the ozone layer is still recovering from damage, caused by chlorofluorocarbons (CFCs), prohibited by the Montreal Protocol 1989 year. Today, the thickness of the ozone layer is 2% lower than the pre-industrial level, and full recovery is expected only until 2066 year. Fugitive emissions from rockets could delay this process for years or even decades depending on the growth rate of the space industry.
Influence of fuel type
The main factors of ozone destruction are chlorine gas and soot particles, that are thrown out by rockets. Chlorine catalytically destroys ozone molecules, and soot heats the middle atmosphere, speeding up chemical reactions, that destroy ozone. Most rocket fuels produce soot, while chlorine is mainly emitted by solid fuel engines. Currently only 6% launches use cryogenic fuel, such as liquid oxygen and hydrogen, which have minimal impact on the ozone layer, but their application is complicated by technological requirements.
Impact of space debris return
The study only considered emissions during launches, but the return of satellites from low orbit also has a significant effect, which burn up in the atmosphere. This process produces metal particles and nitrogen oxides, which catalytically destroy ozone. Metal particles can contribute to the formation of polar stratospheric clouds or serve as surfaces for reactions, which increase ozone losses. These effects remain poorly understood, as most atmospheric models do not yet take them into account. As the number of satellite constellations grows, the impact of debris return will become even more significant.
Solutions
The problem can be mitigated through coordinated action. Monitoring of rocket emissions, reducing the use of fuels, that produce chlorine and soot, promotion of cryogenic technologies and implementation of appropriate regulations will help protect the ozone layer. The success of the Montreal Protocol has shown, that global cooperation can solve environmental threats on a planetary scale. In the new era of space activity, such coordination among scientists, by politicians and the space industry is necessary for the preservation of the ozone layer - one of the most important natural shields of the Earth.
Source: https://phys.org