There was a paper published in June in the peer-reviewed Geophysical Research Letters titled Potential Ozone Depletion from Satellite Demise During Atmospheric Reentry in the Era of Mega-Constellations.

As can be deduced by the lengthy title, scientists have uncovered a new risk coming from the reentry of low-orbit satellites through the atmosphere. Scientists at the University of Southern California Department of Astronautical Engineering are reporting the increased risk to the ozone layer due to the upcoming massive increase in the number of satellites that will be returning to Earth each year.

Low-orbit satellites contain a lot of aluminum, and when a satellite falls to Earth, it creates aluminum oxide, which results in a chemical reaction that kills ozone. The issue doesn’t just arise when a satellite falls to Earth, because the aluminum oxide particles can linger for up to five years as the particles slowly fall out of orbit.

The scientists estimate that in 2022, 18.7 tons of nanoparticles of aluminum oxide were released into the upper atmosphere by falling satellites. They looked forward to the planned obsolescence of satellites, and predict that they could climb to 397 tons per year, which would do massive harm to the ozone layer.

One of the key aspects of low-orbit satellites is that they fall to Earth at the end of their useful life. This feature stops low-orbit space from being oversaturated with obsolete satellites. Keeping unused satellites in orbit increases the risk of satellite collisions and the accumulation of space debris that can make it difficult to launch new satellites into orbit.

Starlink has by far the largest number of low-orbit satellites in orbit, with 6,281 in orbit at the beginning of July. Starlink plans on a useful life of around five years for a satellite. Starlink started launching low-orbit satellites roughly five years ago, so there will be an ever-increasing number of them satellites leaving orbit each year. The real concern comes with Starlink’s future plans. The company plans 11,000 satellites to complete the first big constellation and has long-term plans to have a 30,000 satellite constellation. There are currently about 2,000 satellites launched by others, with plans for many more by companies like Project Kuiper from Jef Bezos.

Depletion of the ozone layer is a serious problem, and a complete destruction of ozone would end most life on the planet since the ozone protects us from cosmic radiation and ultraviolet light coming from the sun. Even a partial depletion means increased skin cancers, cataracts, and damage to marine organisms, plants, and plastics. The planet has come a long way towards stopping the depletion of the ozone layer with the Montreal Protocol in 1989, which phased out CFCs and other chemicals that deplete ozone. This treaty resulted in reducing harmful chemicals by 95%. In 2013, scientists predicted that we were a few decades away from the full recovery of the ozone layer.

This issue points out that there are often unintended consequences from any major deployment of a new technology. It’s impossible to deny the huge benefits of low-orbit satellites, and nobody likely saw this coming. This is obviously an issue that must be addressed now that the problem has been identified. Perhaps it will be as simple as reducing or eliminating aluminum from low-orbit satellites. But the time to fix this is before there are tens of thousands of satellites in orbit.