Space debris falling back to Earth is contaminating the once-pristine upper atmosphere with metallic pollutants as it incinerates during re-entry, according to a new study.
Published in Communications Earth & Environment, the research was led by Robin Wing of the Leibniz Institute of Atmospheric Physics in Germany.
Using highly sensitive laser instruments, the international team detected a plume of lithium contamination and traced it to the uncontrolled re-entry of a discarded upper stage from a Falcon 9 rocket built by SpaceX.
This marks the first direct observational proof that falling space debris leaves a measurable, human-made chemical signature in the upper atmosphere. It is also the first instance in which a pollution plume from a specific re-entry event has been tracked from the ground.
With a surge in planned satellite launches, similar incidents are likely to follow. The findings underscore the urgent need for governments and the space industry to address the issue before it escalates.
A Largely Unexplored Region of The Atmosphere
The layer spanning the upper stratosphere, mesosphere, and lower thermosphere — roughly 80 to 120 kilometres above Earth — remains one of the most poorly understood parts of our planet’s system. It sits too high for weather balloons, too low for satellites, and is too extreme for aircraft to operate in.
Despite this, it plays a vital role in radio and GPS signals, upper-atmospheric weather dynamics, and the health of the stratospheric ozone layer.
The upper atmosphere has remained mostly free from human pollution. However, the modern surge in space activity is introducing increasing amounts of metals and other contaminants from satellites, rocket stages, and orbital debris.
The consequences for the stratospheric ozone layer — essential for shielding life on Earth from harmful ultraviolet radiation — are still unknown. Early evidence, however, suggests there may be reason for concern.
For instance, a 2024 study indicates that aluminium and chlorine released during rocket launches and re-entries could hinder the ozone layer’s recovery.
Meanwhile, soot emitted by rockets is also expected to contribute to warming in the upper atmosphere.
Detecting Lithium Using Lasers
In the new study, researchers employed an advanced laser-based sensor to observe the fluorescence of trace metals in the mesosphere and lower thermosphere. While this system isn’t commercially available, it has the potential to become so.
On 20 February 2025, the team recorded a sharp spike in lithium ions, originating from lithium batteries and metal components of satellites—clearly distinguishable from natural meteoric material.
By applying atmospheric trajectory models, they linked the timing and altitude of the lithium plume directly to the re-entry of a discarded Falcon 9 rocket stage, which burned up while descending through the lower thermosphere into the mesosphere over the Atlantic Ocean, west of Ireland.
A Problem that is Growing Quickly
The satellite population in orbit has surged from just a few thousand a few years ago to around 14,000 today, primarily due to the rise of megaconstellations.
Even more satellites are on the way. SpaceX, for example, has proposed a megaconstellation of up to one million satellites to support space-based data centers. Each of these satellites—and the rockets that deploy them—will eventually re-enter Earth’s atmosphere.
Current projections indicate that by 2030, multiple tonnes of spacecraft debris will incinerate in the upper atmosphere each day.
At present, there are no regulations governing these emissions, few ways to monitor them, and limited scientific knowledge about their potential effects.
The recent detection of lithium shows that re-entry pollutants can be measured and traced to specific events, marking a key step toward holding spacefaring companies accountable.
Global regulatory bodies should be established to coordinate with governments and scientists in creating monitoring networks and instruments to track how this emerging threat affects the atmosphere.
As the space industry expands rapidly, efforts to understand, observe, and regulate upper-atmospheric emissions must advance at the same speed.
—Robyn Schofield, Professor and Associate Dean (Environment and Sustainability, Faculty of Science), The University of Melbourne, and Robert George Ryan, Research Fellow in Atmospheric Composition, The University of Melbourne.
Read the original article on: Sciencealert
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