Changes in Earth’s atmosphere resulting from climate change are working against efforts to clean dangerous space debris out of orbit around Earth.
On the surface, that might be great news for satellite makers, who want functioning crafts to stay in orbit for as long as possible. But there’s a catch: space debris inability to self-clean — a result of excess CO2, which eats away at the density of the upper atmosphere — also means that polluting, dangerous space debris stays in orbit for longer, too.
According to a new study by the British Antarctic Survey, increasing levels of carbon dioxide reduce the density of the upper atmosphere, meaning that objects orbiting close to Earth face less drag and stay afloat longer.
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Overhead, some 5,000 satellites orbit in what’s called low Earth orbit (LEO). Most of these satellites are focused on scientific pursuits, but others are crucial to our global communication networks. The permanently staffed International Space Station (ISS) also calls LEO home.
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LEO ranges in altitude from 100 miles (160 kilometers) up to 1,200 miles (2,000 km) above Earth’s surface. Objects in LEO aren’t slothfully circling Earth, either, they travel at around 15,700 mph (25,000 km/h). But satellites aren’t the only objects that inhabit this region.
Ingrid Cnossen, a research fellow at the British Antarctic Survey, made those conclusions based on computer models of the entire atmosphere. She analyzed the last 50 years of the atmosphere’s evolution and compared that with projections based on future emission scenarios. The model, which looked 50 years into the future based on predictive models, revealed twice as significant thinning of Earth’s upper atmosphere compared to the past 50 years.
“Space debris is becoming a rapidly growing problem for satellite operators due to the risk of collisions,” Ingrid Cnossen, a research fellow at the British Antarctic Survey and the study’s author, said in a statement, “which the long-term decline in upper atmosphere density is making even worse.”
That may be good news for satellite operators, who have lately seen their satellites dropping down faster than ever because of worsening space debris weather. On the other hand, defunct satellites and space debris objects that are slowly making their way down through the atmosphere will keep cluttering their orbits longer. And that means a higher risk of dangerous collisions that could generate massive amounts of dangerous space debris fragments.
Cnossen’s research confirms the belief that, despite their reputation for warming the Earth’s surface, greenhouse gases actually have the opposite impact on the atmosphere.
The worrying changes in atmospheric density will be measurable at altitudes between 56 and 310 miles (90 and 500 kilometers), the British Antarctic Survey said in a statement, and will occur even under moderate greenhouse gas emission scenarios that have been predicted.
As those CO2 particles suck up the limited available heat up there, the atmosphere shrinks and cools, in an effect that ultimately makes for a smoother, longer orbit for satellites, plus the junk caused by old, defunct spacecrafts.
As the upper atmosphere emits heat, it cools down and shrinks. And where it shrinks, space debris objects suddenly have a smoother ride, extending their orbital lifetime. Experts worry that space debris drag reduction can worsen the space debris problem that has concerned the space community for quite a few years now.
“Space debris is becoming a rapidly growing problem for satellite operators due to the risk of collisions, which the long-term decline in upper atmosphere density is making even worse,” Cnossen said. “I hope this work will help to guide appropriate action to control the space debris pollution problem and ensure that the upper atmosphere remains a usable resource into the future.”
And while satellite makers might be happy to see some crafts comfortably cruise around for longer than expected, everyone ultimately stands to lose if space debris gets even more out of hand. New satellites will have a difficult time working in what might pretty much become a close-orbit space debris, and humans, on the ground and in space, could face life-threatening consequences.
The U.S. Global Surveillance Network currently tracks some 30,000 pieces of space debris in Earth orbit larger than 4 inches (10 centimeters). On top of that, about a million 0.4-inch-wide (1 cm) fragments hurtle around the planet, according to the European Space Agency.
The situation is bound to get worse as the number of satellites in near-Earth space quickly rises with the deployment of new constellations. With the increase of defunct objects in orbit, the danger of collisions also rises, leading to a domino effect. Such collisions could create thousands more fragments or space debris, which would then threaten other spacecraft, and so on.
Space agencies as well as private companies are looking at means of removing space debris from low Earth orbit, the region below 600 miles (1000 km), with the help of technology. Still, they need the atmosphere’s help to keep things in check. It now seems climate change might be working against them.