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The growing presence of greenhouse gases (GHGs) in Earth’s atmosphere is not just a terrestrial concern; new research suggests it significantly affects the sustainability of satellite operations in low Earth orbit (LEO). A recent study published in Nature Sustainability reveals that increasing carbon dioxide (CO2) emissions are causing the thermosphere to cool and contract, reducing atmospheric density and, consequently, the satellite carrying capacity of LEO.
How Greenhouse Gases Impact the Thermosphere
The thermosphere, a critical atmospheric layer extending into LEO, is shrinking due to rising CO2 concentrations. Unlike in the lower atmosphere, where CO2 leads to warming, in the upper atmosphere, it enhances infrared radiation cooling, leading to a steady contraction of the thermosphere. This results in a decrease in atmospheric drag, meaning that debris and defunct satellites remain in orbit for longer periods. As the study states, “A consequence of cooling is a contraction of the global thermosphere, leading to reductions in mass density at constant altitude over time.”
The Rising Threat of Space Debris
With reduced drag, space debris accumulates more rapidly, posing a significant threat to active satellites. The study highlights that major fragmentation events, such as satellite collisions and anti-satellite tests, have already created dense debris clusters at critical altitudes (notably around 900 km). Without sufficient atmospheric resistance to naturally deorbit debris, the risk of collisions—potentially triggering the Kessler Syndrome, where cascading collisions generate an uncontrollable debris field—grows exponentially. “Declining mass density in LEO inevitably leads to a more rapid accumulation of orbital debris,” the study warns.
Declining Orbital Carrying Capacity
Using projected CO2 emission scenarios, the researchers introduced the concept of Instantaneous Kessler Capacity (IKC) to estimate how many satellites LEO can safely accommodate without triggering runaway debris growth. Under high-emission scenarios (SSP5–8.5), they found that by 2100, satellite carrying capacity could drop by 50% at solar maximum and up to 66% at solar minimum. “By 2100, considering SSP5–8.5 as the worst-case scenario, a 50% reduction in capacity is observed at solar maximum with a 66% reduction at solar minimum,” the study states. The most affected zone lies between 400–1,000 km, where most operational satellites reside, with a potential 82% reduction in carrying capacity under extreme emission conditions.
This research underscores the urgent need for stricter space traffic management policies and mitigation strategies, such as deorbiting regulations and active debris removal initiatives. Moreover, it highlights an unexpected link between climate change and space sustainability—reducing CO2 emissions may not only benefit Earth’s climate but also help preserve orbital stability for future space operations. As the study concludes, “Continued emissions of GHGs will deplete our collective orbital resource.”
As humanity’s reliance on space-based infrastructure grows, understanding and mitigating the environmental effects on LEO is crucial to ensuring the long-term sustainability of satellite operations.
References: https://www.nature.com/articles/s41893-025-01512-0
https://www.space.com/kessler-syndrome-space-debris
Banner Image: Photo by Jeremy Thomas on Unsplash
