A rocket lifts off from Cape Canaveral. The roar is spectacular, the white streak crosses the blue sky: this time, sixty Starlink satellites have reached orbit. Mission successful. But as the booster lands on the ocean shelf and the technicians celebrate, something remains unsettled. In the stratosphere, between 15 and 50 kilometers above the surface, particles of chlorine and soot begin to float. They don't fall with the rain, they aren't blown away by the wind. They remain. For weeks, sometimes months. And as they circulate around the planet, they break down ozone molecules. One by oneIt happens with every launch. In 2019, there were 102 space launches a year. In 2024, there were 258. By 2030, there could be 2.040.
The ozone layer, which was finally healing after forty years of intensive care, may begin to thin again.
Space launches, the problem that no one regulates
The research comes from an international team led by Laura Revell ofUniversity of Canterbury e Sandro Vattioni ofETH in Zurich. The study published in NPJ Climate and Atmospheric Science He simulated what will happen by 2030 if the growth in space launches continues at this rate. The hypothesized scenario calls for 2.040 annual launches: eight times the number of 2024 launches. The result? Global average ozone thickness would decrease by 0,3%, with seasonal reductions of up to 4% over Antarctica., where the hole still opens every spring.
These numbers seem small. But the ozone layer is still recovering. It's currently about 2% thinner than pre-industrial levels. Full recovery was expected by 2066. With unregulated rocket emissions, that goal could slip by years, perhaps decades. Vattioni explains it bluntly:
“The upper atmosphere lacks the natural removal mechanisms that normally clean the air at lower altitudes. Pollutants remain up to 100 times longer compared to terrestrial emissions”.
Chlorine and soot, the invisible enemies
The main culprits are two: the chlorine gas and soot particlesChlorine comes from solid propellants, those containing ammonium perchlorate. During combustion, they release chlorine, which acts as a catalyst in the stratosphere: it breaks down ozone molecules without being consumed, while continuing to destroy others. The soot produced by most engines heats the atmosphere, accelerating chemical reactions that further degrade the protective shield.
The technical solution already exists: Cryogenic fuels like liquid oxygen and hydrogen have a negligible impact on ozone. The problem? Only 6% of current launches use this technology. Managing cryogens is complex and expensive. The space industry prefers solid propellants, easier to store and use.
The reentry of the satellites makes everything worse
Revell and Vattioni's study considered only emissions during space launches. But there's a second problem, even more difficult to quantify: reentry. Satellites in low orbit have a short lifespan. At 250-600 kilometers above Earth, they still experience friction from the residual atmosphere, which slows them down until they crash. When they burn during reentry, they release nitrogen oxides and metal particles. Nitrogen oxides catalytically destroy ozone. Metal particles contribute to the formation of polar stratospheric clouds, which intensify the loss.
Mega-constellations like Starlink require constant replacementsEvery 5-10 years, the devices need to be replaced. More launches, more satellites, more reentries. A self-perpetuating cycle. "As satellite constellations grow, reentry emissions will become more frequent, and the overall impact on the ozone layer will likely be even greater than current estimates," Vattioni said.
Montreal had worked
In 1987 the world agreed to save the ozone. The Montreal Protocol banned chlorofluorocarbons, those chemicals used in refrigerators and spray cans that were blowing holes in the stratosphere. CFC emissions dropped by 99%The Antarctic hole began to shrink. It worked because all the countries agreed, established clear rules, and controlled the industries.
This time it's different. Space launches have no global rules. Each country launches as it wants, when it wants. SpaceX takes off every two weeks. Amazon prepare the constellation CooperChina responds with Guowang. No one systematically monitors emissions. No one mandates less harmful propellants. The space race became a business before anyone considered the atmospheric consequences.
Space launches: what's to be done?
The study's authors propose solutions: monitoring emissions, reducing fuels that produce chlorine and soot, promoting alternative propulsion systems, and implementing international regulations. All are feasible. But the same kind of global coordination that made Montreal possible is needed. "The Protocol has demonstrated that even global-scale environmental threats can be addressed through global cooperation," write Revell and Vattioni.
“As we enter a new era of spaceflight, the same kind of foresight will be needed.”
The ozone layer is one of Earth's most vital natural shields. It has protected us for millions of years. Forty years ago, we realized we were destroying it, and we took action. Now we're starting over, with a different technology but the same result.
The difference is that this time we already know what's going to happen. And we're going to continue anyway.
