Climate Change Is Making Space More Hazardous for Satellites

Greenhouse gas emissions are altering not just Earth's climate but also the environment of space. For decades, climate change research has focused on the troposphere, the layer of the atmosphere closest to the planet’s surface.

However, recent studies indicate that the thermosphere—which extends into low Earth orbit, where thousands of satellites operate—is also being affected.

Carbon dioxide (CO2) and other greenhouse gases trap heat in the lower atmosphere, leading to global warming. In the upper atmosphere, however, CO2 behaves differently. Instead of trapping heat, it radiates it away into space, causing a cooling effect. As the thermosphere cools, it contracts, reducing atmospheric density at high altitudes. This reduction in density affects satellites and space debris in significant ways.

The thermosphere naturally expands and contracts in response to the Sun’s 11-year activity cycle. When solar activity is low, the thermosphere cools and shrinks, only to expand again when the Sun’s activity increases. But the contraction caused by greenhouse gas emissions is different. Instead of being temporary, this shift appears to be long-term, with implications lasting for centuries.

The contraction of the thermosphere reduces atmospheric drag, the force that slows down satellites and eventually causes them to re-enter and burn up in the atmosphere. With less drag, inactive satellites and debris remain in orbit for much longer. This increases the risk of collisions, creating more debris and making space a more hazardous environment.

Currently, more than 8,000 satellites orbit Earth at altitudes between 300 and 1,000 kilometers. In recent years, the number of satellites has increased dramatically, with over 10,000 now in orbit. Many of these belong to satellite megaconstellations such as SpaceX’s Starlink, which provides broadband internet access from space.

With a growing number of satellites, the likelihood of accidental collisions rises. Each collision generates debris that can remain in orbit for decades or even centuries, further increasing the risk of future collisions.

William Parker, a graduate student at MIT’s Department of Aeronautics and Astronautics, warns, “At the same time, there’s been a massive increase in the number of satellites launched, especially for delivering broadband internet from space. If we don't manage this activity carefully and work to reduce our emissions, space could become too crowded, leading to more collisions and debris.”

A recent study from MIT aerospace engineers estimates that by 2100, the number of satellites that can safely operate in low Earth orbit may decline by 50 to 66 percent due to greenhouse gas-induced atmospheric changes. The researchers used computer models to simulate different emission scenarios and their effects on atmospheric density and satellite collisions.

The team found that if emissions continue to rise, the shrinking thermosphere will significantly reduce the carrying capacity of space. Once a region exceeds its carrying capacity, a runaway chain reaction of collisions, known as the Kessler syndrome, could occur. This would create so much debris that space could become unusable for new satellites.

“More satellites have been launched in the last five years than in the preceding 60 years combined,” says Parker. “One of the key things we’re trying to understand is whether the path we’re on today is sustainable.”

The connection between Earth’s environment and space sustainability is becoming increasingly clear. The thermosphere’s ability to clear space debris naturally is diminishing, making long-term space operations riskier. Matthew Brown of the University of Birmingham emphasizes the importance of sustainability both on Earth and in orbit.

“Often we think only about the ground- or sea-level impacts of climate change, but this research demonstrates that the impacts will reach as high as space,” Brown says.

Experts argue that managing the rapid expansion of satellites in low Earth orbit is crucial. Without coordinated international efforts to limit emissions and regulate satellite deployment, space could become an increasingly dangerous and crowded place.

Dr. Brown warns, “Discussions are already underway about how many satellites can be put into space at any one time. Without checking this proliferation, we are in danger of entering a ‘Kessler syndrome,’ where a chain reaction of collisions causes space to become unusable.”

This research, published in the journal Nature Sustainability, underscores an urgent reality: efforts to curb greenhouse gas emissions are not just necessary for Earth’s climate but also for the sustainability of space. If left unaddressed, climate change could permanently alter the way satellites operate, making space a far less hospitable place for future generations.

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