When we look up at the night sky and see a satellite glide past, we might not consider climate change or the ozone layer.
Space may feel separate from the environmental systems that sustain life on Earth. But increasingly, the way we build, launch and dispose of satellites is starting to change that.
Most of the almost 15,000 active satellites in orbit around the Earth are part of “mega-constellations” in which each has a service life of only a few years.
New satellites must be quickly launched as replacements. To avoid leaving old, dead satellites in Earth’s already-crowded low orbits, most satellite operators deliberately de-orbit them into the upper atmosphere.
There, they burn up or break apart into smaller pieces: a process known as “demisability”. In effect, satellites have become part of the throwaway culture.
That approach is now being taken to a vastly larger scale. We are concerned about the implications for Earth’s climate and atmosphere.
Global regulation is needed to manage satellite launches and protect the atmosphere and night sky. Photo / Getty Images
A sleeper risk for our climate and ozone layer
Last month, SpaceX applied to the US Federal Communications Commission (FCC) for permission to launch one million more satellites for untested artificial intelligence (AI) data centres.
That sheer number isn’t the only issue. SpaceX’s Starlink V2 “mini”-satellites weigh about 800kg, roughly the mass of a small car, with later versions expected to reach around 1250kg. The planned V3 satellites are larger still, comparable in scale to a Boeing 737.
Rocket launches already contribute to climate change and ozone depletion. Scaling them up to deploy a million aircraft-sized satellites would push upper-atmosphere heating and ozone loss far beyond previous estimates, with the steady burn-up ofdead satellites compounding the impacts.
This comes as dust from burned satellites is already being found in the atmosphere. In 2023, scientists studying aerosols in the upper atmosphere found metals from re-entering spacecraft. Just recently, lithium has been detected from the uncontrolled re-entry of a Falcon 9 rocket.
This is just a fraction of what is to come if planned mega-constellations go ahead – and SpaceX is far from the only player. Other operators worldwide have already asked for a combined total of over one million satellites.
All the while, the full environmental consequences remain poorly understood because satellite builders rarely disclose what their spacecraft are made of.
Scientists assume a large fraction is aluminium, which burns up into alumina particles, but the exact mix of materials – and the size of the particles produced – remains poorly constrained.
SpaceX plans to launch one million more satellites, potentially impacting climate and increasing debris. Photo / Getty Images
But we know the very smallest particles, finer than a human hair, can stay suspended in the atmosphere for years, contributing to ozone depletion and climate change.
Following similar assumptions to a previous study, we estimate that a million satellites could mean that a teragram (one billion kilograms) of alumina accumulates in the upper atmosphere – enough, alongside launch emissions, to significantly alter atmospheric chemistry and heating in dramatic ways we do not yet understand.
There is no public mandate for a single company in one country to make changes on that scale to the planet’s atmosphere.
The consequences are not confined to the atmosphere. Not all re-entering satellites burn up; debris is already hitting the ground and the chance of a casualty from mega-constellation re-entries is now about 40% per five-year cycle – rising for both people and aircraft as more satellites are added to orbit.
In space, the picture is no less stark: the Outer Space Institute’s Crash Clock suggests a collision would occur within 3.8 days if satellites stopped avoiding each other.
Many experts agree we are in the early stages of the Kessler Syndrome: a cascading chain reaction of collisions that multiplies space debris.
Our skies are not a dumping ground
Our night sky, especially cherished in New Zealand, is one of the few things everyone on Earth still shares.
According to simulations built by astronomers, constellations on the scale proposed by SpaceX would fill the sky with many thousands of satellites visible to the naked eye anywhere on Earth. Eventually, there could be more visible satellites than visible stars.
These pieces of shredded debris, which came from an expendable trunk module attached to one of SpaceX’s Dragon spacecraft, fell on farmland in Saskatchewan, Canada in April 2024. Photo / Samantha Lawler, CC BY-NC
For scientists, observing the deaths of stars and searching for new planets would become much harder. Stargazing, astrotourism and cultural astronomy would similarly be disrupted worldwide.
All of this means the FCC’s ruling on the SpaceX proposal, now open to public submissions, could affect everyone – whether through changes to the atmosphere, growing collision risks in orbit or the loss of an unspoiled night sky.
One solution being discussed is to dispose of dead satellites in orbits away from Earth. But this would require much more fuel per satellite to escape Earth’s gravity, increasing both payload and the environmental impact of rocket launches. Some debris would still return to Earth.
With SpaceX and others planning rapid expansion, global regulation is needed: in an uncapped system, regulating one firm just shifts the problem elsewhere. As the largest operator, SpaceX is best placed to lead an environmentally sustainable solution, just as chemical company DuPont did with phasing out CFCs in the 1980s.
A first step is to define a safe atmospheric carrying capacity for satellite launches and re-entries. Environmental assessments should cover the full life cycle, including atmospheric effects, and address both orbital safety and impacts on cultural and research astronomy.
Whatever the regulatory outcome, using the atmosphere as a crematorium for satellites at this scale cannot be a solution.
Laura Revell is Professor of Atmospheric Chemistry at the University of Canterbury; Michele Bannister is Associate Professor in Planetary Astronomy at the University of Canterbury; and Samantha Lawler is Associate Professor in Astronomy at the University of Regina in Canada.
This article is republished from The Conversation under a Creative Commons licence. Read the original article here.