About 13,000 satellites currently orbit Earth, roughly 10,000 of which are operational. But that number is set to skyrocket, with a staggering 50,000 new satellites on track to join them by 2030.
The dramatic increase is due to the rise in internet-beaming megaconstellations of satellites, such as SpaceX’s Starlink. Out of almost 8,000 satellites now in low Earth orbit (altitudes typically below 2,000km or 1,200 miles), nearly 6,500 are Starlink satellites.
SpaceX already has the go-ahead to deploy 12,000 satellites and is seeking approval for 30,000 more. Meanwhile, other companies, including Amazon, are planning megaconstellations of their own.
The upshot: low Earth orbit is becoming increasingly cluttered. As well as raising the likelihood of collisions, there’s mounting concern among scientists that megaconstellations could damage the critical layer of ozone that shields Earth from harmful UV radiation.
Decommissioned satellites burn up as they re-enter Earth’s atmosphere, releasing tiny particles of aluminium oxide. These particles are potent catalysts for chemical reactions that eat away at the ozone layer.
But the particles aren’t consumed in these reactions, so they can spend decades destroying more and more ozone.
A typical 250kg (550lbs) satellite generates around 30kg (66lbs) of aluminium oxide particles, according to research published in 2024 in the journal Geophysical Research Letters.
By the time the planned megaconstellations are fully deployed, decaying satellites could inject 360 tonnes of aluminium oxides into the upper atmosphere each year – an increase of 646 per cent over natural levels.
Part of the problem is that internet satellites in low Earth orbit are incredibly short-lived.
Starlink satellites, which orbit at about 550km (340 miles), would be pulled out of orbit by atmospheric drag within five years if SpaceX didn’t proactively deorbit them first. The company is then compelled to launch new satellites to replace them, perpetuating the cycle.
Scientists project that dozens of satellites will be retired each day over the coming decade, potentially releasing a continuous stream of burnt-up materials into the atmosphere. By comparison, the average week saw around 12 re-entries in 2023 (up from just 1.3 in 2019).
It’ll take decades to see the full impact of today’s satellite re-entries on the ozone layer.
Dying satellites create aluminium oxide particles in the mesosphere, 50–85km (30–50 miles) above Earth’s surface. But the particles take up to 30 years to drop to the mid-stratosphere (15–30km/about 10–20 miles), where the ozone layer is located.
For now, the impact of satellite combustion on the ozone layer is likely fairly small, but the rapid proliferation of megaconstellations could derail decades of international collaboration to repair the ozone hole.
What’s missing so far is definitive, in-situ measurements that directly link deorbiting satellites to ozone destruction. An upcoming study by a group that includes Airbus, the Secure World Foundation and the University of Southampton will be the first to collect such data and quantify the risk.
This article is an answer to the question (asked by Claudine Best, Dorset) 'Are satellites burning up in the atmosphere bad for the environment?'
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