Greenhouse gas emissions may drastically reduce the number of satellites that can safely orbit Earth, according to MIT-led aerospace engineers. This news could spell trouble for essential space-based services, including internet and weather forecasting.
Greenhouse gas emissions aren’t just heating up the Earth’s surface; they’re also impacting space. Researchers led by MIT have discovered that these emissions are altering the environment of near-Earth space, potentially reducing the number of satellites that can operate safely in the coming decades.
Published in Nature Sustainability, the study demonstrates that carbon dioxide and other greenhouse gases cause the upper atmosphere, specifically the thermosphere, to contract. This contraction lowers atmospheric density, which subsequently diminishes atmospheric drag — a force that helps pull aged satellites and debris down, where they burn up. With less drag, space junk remains in orbit longer, drastically increasing the likelihood of collisions.
The research team predicts a grim future. Their simulations indicate that by the year 2100, the carrying capacity for satellites in low-Earth orbit could be reduced by 50-66 percent due to the effects of greenhouse gases.
“Our behavior with greenhouse gases here on Earth over the past 100 years is having an effect on how we operate satellites over the next 100 years,” study author Richard Linares, an associate professor in MIT’s Department of Aeronautics and Astronautics (AeroAstro), said in a news release.
This study implies far-reaching consequences for the technologies we rely on daily, from weather forecasting and GPS navigation to global communications and banking.
“The upper atmosphere is in a fragile state as climate change disrupts the status quo,” added lead author William Parker, a graduate student in AeroAstro. “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.”
During the 11-year solar cycle, the thermosphere naturally expands and contracts as the Earth’s outermost atmosphere warms and cools in response to solar activity.
However, the trend of the last few decades indicates that greenhouse gases might now be playing a more significant role. Scientists have observed changes in satellite drag that seem to be driven by these greenhouse emissions rather than natural solar activities alone.
“The sky is quite literally falling — just at a rate that’s on the scale of decades,” Parker added.
The MIT team developed simulations incorporating different greenhouse gas emission scenarios to estimate future orbital dynamics and potential satellite collisions.
Today, there are over 10,000 operational satellites in low-Earth orbit, a region extending up to 1,200 miles from the Earth’s surface. These satellites cater to essential services like internet provision, navigation systems and weather forecasting. The exponential increase in satellite launches, especially by megaconstellations like SpaceX’s Starlink, has already crowded this orbital region significantly.
“More satellites have been launched in the last five years than in the preceding 60 years combined,” added Parker. He emphasized the importance of understanding whether our current path is sustainable.
The researchers used ecological models of “carrying capacity” to predict the number of satellites each altitude could accommodate, considering different emission scenarios. By comparing emission levels from the year 2000 with potential future increases, they found that growing emissions sharply cut the carrying capacity across various altitudes in low-Earth orbit.
The projections indicate that if the carrying capacity is exceeded, even in localized zones, we could face a “runaway instability” or cascading collisions that generate debris making those orbital regions unusable. These findings underscore the urgency of addressing greenhouse gas emissions and managing satellite launches carefully.
“We rely on the atmosphere to clean up our debris. And if the atmosphere is changing, then the debris environment will change too,” Parker added. “We show the long-term outlook on orbital debris is critically dependent on curbing our greenhouse gas emissions.”
Co-authored by Matthew Brown of the University of Birmingham, this research calls attention to a dimension of climate change that reaches beyond our planet’s surface.