Thousands of satellites that burn up in Earth’s atmosphere are leaving more than just streaks of light in the sky.
A groundbreaking study published in the Journal of Geophysical Research: Atmospheres has revealed that dying satellites – those burning up on re-entry after completing their missions in orbit – are releasing pollutants that could have alarming consequences for both the climate and ozone layer.
As satellite megaconstellations grow exponentially, the problem is no longer confined to a niche realm of astrophysics. It’s rapidly becoming a global environmental issue.
Today, there are more than 9,000 satellites orbiting Earth and by 2040 that number is predicted to swell to over 60,000. The driving force behind this growth is the rapid deployment of government and commercial satellite constellations, primarily for broadband internet coverage by companies such as SpaceX and Amazon.
But, as the saying goes, what goes up must come down – and when these satellites complete their missions after relatively short lifetimes, they are routinely deorbited to burn up in the atmosphere.
While this may seem like a tidy solution, it’s anything but clean. The study, led by atmospheric scientist Jamie Shutler and colleagues, finds that re-entering satellites release thousands of tonnes of metal particles into the stratosphere every year.
Chief among these is aluminum oxide (Al₂O₃), a substance with the potential to alter temperature patterns and disrupt delicate atmospheric chemistry.
The authors estimate that by 2040 as many as 10,000 metric tonnes of aluminum oxide could be entering the upper atmosphere annually. This figure represents a staggering increase compared to today’s levels and signals a future where human-made atmospheric contamination could rival or exceed that of natural processes like volcanic eruptions.
Aluminum oxide is no benign byproduct. According to the study, its presence can cause localised heating of up to 1.5C in the middle and upper atmosphere.
“These temperature changes could disrupt wind patterns and other critical dynamics of the stratosphere,” the authors warn.
Perhaps more disturbingly, these disruptions could delay the recovery of the ozone layer – a thin but vital shield that protects life on Earth from harmful ultraviolet radiation.
In an unusually short three paragraph article on its website The Guardian, in summarising the findings, quotes Shutler as saying: “This is a new, emerging chemical pathway that is completely anthropogenic. We are fundamentally changing the chemistry of the atmosphere in a way that has not been considered before.”
The satellite industry has long viewed atmospheric re-entry as a convenient and eco-friendly solution to space junk. But as this study makes clear, the process may be quietly shifting the baseline of Earth’s climate systems.
Particles produced during re-entry are not merely disbursed and forgotten. Instead, they form persistent aerosols that can act as radiative agents – essentially reflecting or trapping heat – while also playing a role in catalysing chemical reactions that destroy ozone.
Aluminum is not the only concern. The study also highlights the release of other metals such as titanium, iron, copper, and lithium – all of which have their own complex chemical interactions and unknown long-term impacts.
The exact consequences of this metallised upper atmosphere are still being modelled, but early signs point to a troubling new front in humanity’s planetary impact.
Researchers also note the increasing role of some rocket launches, particularly from private companies, which contribute additional pollutants like black carbon. Such compounds rise into the stratosphere, where they can remain for years, compounding the problem.
A 2022 study by the US National Oceanic and Atmospheric Administration (NOAA) warned that soot from rockets alone could increase stratospheric temperatures and disrupt polar vortexes. The new satellite re-entry data adds another layer to this growing concern.
Ironically, many of the satellites responsible for these emissions are part of systems designed to monitor and combat climate change. In attempting to connect the world and collect vital environmental data, we may be undermining the very systems that sustain life on Earth.
The implications of the study are sobering. The scientific community and regulatory bodies have, until now, paid scant attention to the effects of mass satellite re-entry. That’s likely to change. As one of the study’s co-authors bluntly put it: “We’re geoengineering the stratosphere without realising it.”
So, what now? The researchers call for urgent reforms to how we manage satellite end-of-life processes.
Alternatives could include designing spacecraft with minimal pollutant output on re-entry, retrieving and disposing of satellites differently, or even developing reusable systems that don’t require destructive descent at all.
These options will require international cooperation and new frameworks for space governance – something the UN’s Committee on the Peaceful Uses of Outer Space has only recently begun to explore.
Earth’s climate crisis has taught us at least one painful lesson: seemingly invisible emissions, once dismissed or underestimated, can have catastrophic consequences. Now, with space becoming the next industrial frontier, we must apply that lesson to the skies above.
Satellites may be our eyes in the heavens, but their burning remains are falling into our future. The time to act is now, while we still have the tools to prevent a new kind of environmental crisis.
As the paper’s authors conclude: “The cumulative effect of satellite re-entries must be taken seriously as part of Earth’s changing atmospheric budget.”
If we fail to heed this warning, the sky itself may become the next casualty of human excess.
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Article references:
Journal of Geophysical Research: Atmospheres - Investigating the Potential AtmosphericAccumulation and Radiative Impact of the Coming Increase in Satellite ReentryFrequency
The Guardian - Dying satellites can drive climate change and ozone depletion
