Space

Returning satellites (even Musk's) pollute the Earth's upper atmosphere, and that is a serious danger

Several substances have negative effects on the mesosphere and thermosphere, between 80 and 120 above sea level. Also affecting the ozone layer that protects us from ultraviolet rays

by Leopoldo Benacchio

20 February 2026

La scia lasciata dal rientro in atmosfera di un Falcon 9 sopra Berlino nel 2025, 30 secondi di esposizione

3' min read

Translated by AI

Versione italiana

3' min read

Translated by AI

Versione italiana

If a rocket passes over your head as it's falling back to Earth, you're usually glad it didn't hit you - it's a normal reaction. But for researchers at the emblazoned Leibniz Institute of Atmospheric Physics in Rostock, a Hanseatic city in northern Germany, it was a boon. And in the middle, as almost always in these years, is Elon Musk and one of his Falcon 9 rockets.

Their study, published these days in the leading journal in the field: Communications Earth & Environment, shows that the rain of space debris returning to Earth, as it burns as it re-enters, also introduces nasty metal pollution into the all-important upper atmosphere, between 80 and 120 kilometres above the ground.

A disturbing discovery

At the Rostock Institute, continuous measurements of the atmosphere are carried out using sophisticated lasers that are directed at different heights above the ground. In the course of this routine activity, they became aware last year of a very significant increase in the amount of lithium in that region, almost a cloud of this element, which is used today for all technology, that had been standing at that height for some time.

La sede dell’Istituto per la Fisica dell’Atmosfera a Rostock

What could have happened, they wondered. With meticulous measurements, they reconstructed the course followed by the upper stage of a Falcon 9 rocket from Space X, in uncontrolled re-entry, and found that it was 'the culprit'. Using a model of the possible trajectory of a re-entering space body, they arrived at the solution: that piece of SpaceX's rocket as it passed through the thermosphere about 100 kilometres above Earth, over the Atlantic Ocean, west of Ireland, had also burnt out the lithium batteries contained in the second stage.

Of course no one could doubt that these episodes, increasingly frequent as launches number in the hundreds each year, are not good for the atmosphere, already battered by human activity, there are various studies now, but this is the first observational evidence that re-entering space debris causes a phenomenon, detectable from the ground.

The mesosphere and thermosphere, between 80 and 120 kilometres from Earth, is one of the least studied parts of our atmosphere: balloons cannot reach it and it is too shallow for satellites, which would not be able to remain in a stable orbit. On the other hand, those layers are crucial for us, for radio communications, the GPS and especially for the evolution of atmospheric ozone.

We are contaminating the upper atmosphere

It is not good news, therefore, that this part of the atmosphere, which until now was free of any contamination, is now, thanks to increasing space activities, which are very useful for that matter, being ruined by quantities of metals and other things that space debris puts into it. There is fear, due to the increase in chlorine and aluminium as well, for the stratospheric ozone layer, which is essential to protect life on Earth from the action of tremendous ultraviolet radiation. The role of chlorine and aluminium, released by the many launches, has not yet been quantified either, but the initial results are cause for concern.

Un pezzo di secondo stadio di un vettore di lancio ritrovato a terra in Polonia nel 2025

This is quite scary because already today the number of satellites has increased dramatically, we are at around 14,000, but in the near future we are talking about satellite constellations in the tens of thousands, even without reaching the phantasmagorical million satellites predicted by Elon Musk. So we have predictions, not pretty, of thousands of tonnes of spacecraft materials that will burn up in the upper atmosphere on their way back to earth, in a controlled or uncontrolled manner. Moreover, this is in addition to the thousands of tonnes of space material of natural origin, dust or micrometeorites, that fall on our planet every year, without us noticing.

The alibi for not addressing the problem, with an appropriate and shared set of rules, is no longer there: we have measured that the effect is there, and it hurts. We must move quickly and positively.