Rocket Launches Threaten Ozone Layer Recovery

The escalating pace of rocket launches globally poses a significant threat to the recovery of the ozone layer, according to a new study. This concern, long underestimated, demands immediate, coordinated action to mitigate potentially severe environmental consequences.

Fueling the rapid expansion of low Earth orbit satellite constellations, the burgeoning space industry is launching more and more rockets into the atmosphere. While technological advancements promise progress, environmental concerns stemming from these developments are growing.

Rocket launches and the subsequent re-entry of space debris release pollutants directly into the middle atmosphere, where they can compromise the ozone layer, crucial for shielding Earth from harmful ultraviolet (UV) radiation. The effects of such pollution are only beginning to be understood, and researchers are racing to catch up.

Early research into rocket emissions dates back over three decades, but the impacts were initially considered minimal. However, with launch activity skyrocketing, this perception is shifting. In 2019, there were 97 orbital rocket launches worldwide. By 2024, this number had exploded to 258, with projections indicating continued rapid growth. This unexpected anomaly calls for immediate reaction.

A Concern Long Ignored

Due to the lack of rain or other cleaning processes in the middle and upper atmosphere, emissions from rockets and re-entering space debris can linger up to 100 times longer than ground-based pollutants. Although most launches occur in the Northern Hemisphere, atmospheric circulation distributes these contaminants globally, impacting the entire planet.

To assess the long-term effects of increasing rocket emissions, a recent study published in npj Climate and Atmospheric Science, led by Laura Revell from the University of Canterbury, employed a sophisticated chemistry climate model. The model simulated the impact of projected rocket emissions on the ozone layer by 2030.

Under a growth scenario projecting 2,040 annual launches in 2030—roughly eight times the 2024 figure—the model predicts a global average ozone thickness decline of nearly 0.3%. More alarming are the seasonal reductions of up to 4% over Antarctica, where the ozone hole reappears each spring.

While these figures might seem small at first glance, it’s crucial to acknowledge that the ozone layer is still recovering from damage inflicted by long-lived chlorofluorocarbons (CFCs), successfully banned under the 1989 Montreal Protocol. The ozone layer’s thickness is currently still around 2% below pre-industrial levels, with full recovery not expected until approximately 2066. This research suggests that unregulated rocket emissions could delay that recovery by years or even decades, depending on the industry’s growth trajectory.

A resident of Ushuaia, Argentina, reported seeing more intense sunburns in recent years despite consistent sunscreen use. “It raised more questions than answers,” she said, reflecting the community’s growing unease.

The Fuel Factor

The primary culprits in ozone depletion from rocket emissions are chlorine gas and soot particles. Chlorine acts as a catalyst, destroying ozone molecules directly, while soot particles warm the middle atmosphere, accelerating chemical reactions that deplete ozone.

While most rocket propellants release soot, chlorine emissions are largely associated with solid rocket motors. Cryogenic fuels like liquid oxygen and hydrogen have a negligible effect on the ozone layer, but their technological complexity limits their use. Only around 6% of current rocket launches utilize this technology.

Re-entry Risks: The Unknowns

The current study focused on emissions from rockets during their ascent, but that’s only half the story. Most satellites in low Earth orbit eventually re-enter the atmosphere at the end of their lifespan, burning up in the process. This raises an issue that isn’t being talked about.

This burning process generates additional pollutants, including metal particles and nitrogen oxides, thanks to the intense heat. Nitrogen oxides are known ozone depleters, and metal particles may contribute to the formation of polar stratospheric clouds or act as reaction surfaces, both intensifying ozone loss.

These re-entry effects are poorly understood and not yet integrated into most atmospheric models. As satellite constellations increase, re-entry emissions will become more frequent, potentially leading to an even greater impact on the ozone layer than current estimations suggest. Science must address these knowledge gaps.

The current situation raises a lingering question: will we react proactively, or wait for irreversible damage?

• Key Findings
• Projected rocket emissions could delay ozone layer recovery.
• Solid rocket motors are a major source of chlorine emissions.
• Re-entry effects are poorly understood and pose additional risks.
• International cooperation is crucial for effective regulation.

A Call for Foresight and Coordination

A launch industry that avoids ozone-damaging effects is achievable. Key steps include monitoring rocket emissions, minimizing chlorine and soot-producing fuels, promoting alternative propulsion systems, and implementing appropriate regulations.⁴ This requires coordinated action among scientists, policymakers, and industry stakeholders.

The Montreal Protocol serves as a successful example of addressing planetary-scale environmental threats through global cooperation. To mitigate the harmful effects of space activity on the ozone layer, this same foresight and international coordination are vital.

One space enthousiast on X.com commented: “It is important to keep exploring, but doing it responsibly must be our priority.” A contrasting view point came from a Facebook group where somebody said: “They want to limit space exloration now? What about all the polution cars make?”.

Here is a list of measures we could take to avoid damading the ozone layer:

1. Monitoring rocket emissions.
2. Minimizing the usage of chlorine and soot-producing fuels.
3. Promoting alternative propulsion systems.
4. Implementing the necessary and appropriate regulations.