We have solved the problem of space junk by burning it. A SpaceX lithium trail just proved to be a terrible idea

For decades, the aerospace industry has had a consensus solution to the problem of space junk: burn it. A fairly simple phenomenon that is based on the satellite reentry when it ends its useful life in the atmosphere so that it begins to suffer friction and completely disintegrates. But the reality is that we are facing a huge problemsince physics reminds us that matter is neither created nor destroyed.

We have captured him. Science is realizing that we are not removing space junk, we are just vaporizing it into metallic aerosols that are changing the chemistry of our own sky. And the definitive clue to this problem was found on the night of February 19, 2025where a team of German researchers pointed a laser into the sky over Kühlungsborn.

What they detected in this case at about 100 kilometers altitude, in the thermosphere, was something that should not be there, since there were large amounts of lithium. And it wasn’t there for no reason, since it just coincided hours before with the re-entry of a SpaceX Falcon 9 rocket which had disintegrated over the Atlantic between Ireland and the United Kingdom.

Something new. The signal measured in this case was not very subtle, since was 10 times bigger to the usual concentration in that region, and this finding was collected in an article because it marks a great milestone: it is the first time that the metallic contamination released from a specific piece of space junk at the exact moment of burning has been observed “live” and from Earth.

The metallic iceberg. The incident with this Falcon is not something isolated in our society, but is a symptom of the structural change we are experiencing. In 2023, a team of researchers already used different devices to be able analyze more than 50,000 aerosol particles in the stratospherewhich is the layer where our ozone layer resides, at about 15-30 km altitude.

What did they see? Historically, the metals found in the stratosphere came from meteorites that entered our planet. But today it is estimated that 210 tons of aluminum per year in the atmosphere comes from the disintegration of satellites and rockets, compared to the 20 tons per year that vaporize naturally from meteors.

But lithium is not the only metal in the atmosphere of our planet, since scientists have detected more than twenty elements, among which aluminum, copper, lead or silver stand out… This is something that does not fit with the normal composition of meteorites, but it does coincide with the materials that different aerospace companies use to create their rockets and satellites.

There is no planning. The pace of launches has skyrocketed in recent years, and if today we are close to 10,000 objects orbiting the Earth, we have to know that only Starlink aspires to have more than 40,000 satellites in Earth orbit low. But the problem is that the useful life of these devices is short, so their inevitable fate is to end up vaporized over our heads.

Its effects. Science here is quite clear that the effects of filling the stratosphere with these metals are currently unknown. But the projections suggest that we should not be calm because elements such as aluminum and copper are important catabolizers that can affect the delicate ozone layer.

In addition to this, metallic particles can act as special condensation nuclei, altering the microphysics of polar stratospheric clouds. And if that were not enough, adding anthropogenic material to sulfuric acid aerosols changes their size and ability to scatter sunlight. Ironically, we are altering the reflectivity of the stratosphere, the same layer that some scientists want to use for climate geoengineering, without knowing what the consequences will be.

The planetary limit. The models here suggest that, if the planned megaconstellations materialize, the fraction of stratospheric particles contaminated with aluminum from satellites will rise from the current 10% to around 50%. In other words, the load of metals in the stratosphere could grow by around 40% compared to natural levels.

Here for years space agencies have assumed that disintegrating satellites was a completely harmless and clean practice. The example of the Falcon 9, which has validated the warnings of the scientific community, shows us that the Earth’s orbit and our atmosphere make up a connected ecosystem. In this way, launching tens of thousands of objects into space and then burning them on our own roof may be a solution to keep space clean, but we are dirtying the sky in return.

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