Rocket launches threaten Earth's ozone recovery

The growing number of rocket launches may pose a threat to Earth’s ozone layer. While the expanding space industry holds great promise, researchers warn that its environmental impacts are being overlooked.

With thousands of satellites now cluttering low Earth orbit, emissions from launches and back-end debris are making alarm bells ring over atmospheric well-being.

Space boom comes with a cost

A team of scientists from the University of Canterbury and ETH Zurich investigated how pollution from rocket launches and falling space junk could slow the ozone layer’s recovery.

The researchers used a chemistry-climate model developed at ETH Zurich and the Physical Meteorological Observatory in Davos (PMOD/WRC) to forecast rocket emission impacts through 2030.

Back in 2019, there were only 97 orbital launches. By 2024, that number had nearly tripled to 258 – and it’s expected to rise to over 2,000 per year by the end of the decade.

This increase is concerning because emissions in the upper atmosphere linger much longer than those released at ground level.

Without natural washout processes like rain or clouds, these pollutants can circle the globe and remain in the air for years.

The ozone layer’s fragile recovery

The model predicts that, if current growth trends continue, the global ozone layer could thin by nearly 0.3 percent by 2030. Over Antarctica, seasonal losses could reach up to four percent.

These might seem like small numbers, but context matters. The ozone layer is still recovering from the damage caused by chlorofluorocarbons (CFCs), banned in 1989 by the Montreal Protocol.

Global ozone levels are still about two percent below pre-industrial levels and aren’t expected to fully recover until 2066.

According to the researchers, unregulated rocket emissions could delay this timeline by several years – or even decades.

Why the ozone layer still matters

The ozone layer may seem like a distant part of the atmosphere, but it plays a vital role in shielding life on Earth. It absorbs most of the sun’s harmful ultraviolet (UV) radiation, which can cause skin cancer, cataracts, and immune system damage in humans.

It also affects ecosystems, particularly marine life, by influencing the health of phytoplankton – tiny organisms that form the base of the ocean’s food chain.

Even modest declines in ozone can boost the amount of UV radiation that reaches the Earth’s surface. That is to say, any quantifiable decrease is more than a number – it’s an alarm.

Ongoing harm could bring about additional UV-related health threats, upset delicate ecosystems, and undermine the gains achieved since CFCs were banned.

Simply put, every percentage point of recovery counts, and every delay threatens human and environmental well-being.

Fuel type matters more than you think

The problem lies mainly with emissions of chlorine gas and soot. Chlorine breaks apart ozone molecules, and soot particles heat the middle atmosphere, speeding up ozone-damaging reactions.

Solid rocket motors are the main source of chlorine emissions, while most rocket types release soot.

Only rockets using cryogenic fuels – like liquid oxygen and hydrogen – are nearly ozone-neutral. But these fuels are tricky to handle, and only about 6 percent of current launches use them.

That means the vast majority of launches still contribute to ozone depletion.

Re-entry: the hidden threat

The study focused on emissions during rocket ascent, but what about the return journey? Most satellites burn up when they re-enter the atmosphere, releasing nitrogen oxides and metal particles.

Nitrogen oxides are already known to harm the ozone, while metals could form clouds or act as chemical surfaces that accelerate ozone loss.

Scientists still poorly understand these effects and often leave them out of climate models. But with satellite constellations growing rapidly, more and more debris will re-enter the atmosphere, making this an urgent area for further research.

Clean fuels offer a path

“There is a risk that the rapid rise in global rocket launches could slow the recovery of the vital ozone layer,” said Sandro Vattioni. “The problem is being underestimated – yet it could be mitigated by forward-looking, coordinated action.”

The researchers believe there’s still time to act. Better monitoring of emissions, using cleaner fuels, and encouraging the switch to cryogenic systems could help protect the ozone layer.

Setting international regulations would allow the space industry to grow sustainably.

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