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In 2016, European Space Agency astronaut Tim Peake shared a Photo a quarter-inch dent in a window on the International Space Station (ISS). The guilty? A small patch of space debris.
The piece of debris, perhaps a paint flake or a piece of metal from a satellite, was only a few thousandths of a millimeter in diameter – not much larger than a single cell of E. coli.
But how can something so small cause visible damage?
“It all comes down to speed,” said Vishnu Reddy, an astronomer at the University of Arizona. Objects at the altitude of the ISS and most other satellites – approximately 400 kilometers above Earth – revolve around our planet once every 90 minutes, depending on the European Space Agency. That’s over 15,600 mph (25,200 km / h), 10 times the speed of an average bullet fired at Earth, wrote Robert Frost, instructor and flight controller at NASA. Quora.
Related: What would happen if you shot a gun in space?
The energy of an impact is not only related to the size of an object; speed (speed and direction) is just as important. This is why a small bullet can cause so much damage; by moving at a sufficiently high speed, any object can be dangerous, Reddy told Live Science.
Keep in mind that speed is additive, said Kerri Cahoy, associate professor of aeronautics and astronautics at the Massachusetts Institute of Technology. So if two objects move closer to each other when they collide, it increases the energy of their impact.
“Think of it like you’re driving on a freeway,” Cahoy told Live Science. Two fast cars moving in the same direction could touch each other and “barely kiss,” she said. But if a vehicle – even a light one, like a motorcycle – collides with a car while accelerating in the opposite direction, it could be disastrous for both drivers.
Likewise, in space, a fast moving paint spot that collides with the ISS can leave a relatively large mark.
In space, satellites, spacecraft and debris revolve around many different paths; while one object could orbit horizontally around the equator, another could loop vertically around the poles. Some objects even move “downshift”, which means they rotate against Earth’s orbit. As more and more debris clogs space, Earth’s low orbit (in which the ISS rotates) turns into a crowded highway at rush hour. “There may be a potential for significant damage,” Cahoy told Live Science.
Astronauts aboard the ISS were fortunate that a larger piece of debris did not hit their window. A microbe-sized fragment may leave only a bump, but a pea-sized fragment can disable critical flight systems, according to the European Space Agency. A piece of debris the size of a ping-pong ball? “It would be catastrophic,” Reddy said. At this size, space debris could cause the space station to depressurize rapidly, making it impossible for astronauts to breathe on board, Reddy said.
The space junk is a growing problem. Earth’s orbit contains at least 128 million pieces of debris, 34,000 of which measure more than about 10 centimeters, according to the Natural History Museum in London – and these are just the fragments that are large enough to be detected. These smaller pieces form when satellites naturally survive under extreme ultraviolet radiation, when larger space debris collides, or when satellites are intentionally destroyed. The larger pieces include 3,000 abandoned satellites, as well as bolts and other parts thrown by spacecraft during launches.
By tracking space debris, scientists can tell countries and businesses when to maneuver a spacecraft out of the path of an accelerating piece of debris, Reddy said. The ISS has carried out 25 of these maneuvers since 1999, according to the Natural History Museum. And researchers are developing ways to fish the waste out of space, such as using hooks, nets and magnets to bring it back to Earth’s atmosphere.
Too much space waste could make it dangerous for humans to use Earth’s orbit for satellites and other types of spacecraft. We’re a long way from that point now, but it’s important to get ahead of the space debris problem to avoid any further build-up, Reddy said.
“We rely on space for so many things: communication, weather forecasting, banking, entertainment and the military,” he said. “In terms of our progress as a civilization, we would take many steps back if we didn’t have access to space.”
Originally published on Live Science.
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