In 2016, European Space Agency astronaut Tim Peake shared one photo of a quarter-inch dent in a glass window of the International Space Station (ISS). The guilty? A small piece of space junk.
The piece of debris, perhaps a chip of paint or a metal fragment from a satellite, was only a few thousandths of a millimeter wide – not much bigger than a single cell of E coli
But how can such a small thing do visible damage?
“It all comes down to speed,” said Vishnu Reddy, an astronomer at the University of Arizona. Objects at the height of the ISS and most other satellites – about 400 kilometers above Soil – rotate around our planet every 90 minutes, according to the European Space AgencyThat’s over 15,600 mph (25,200 kph), 10 times the speed of an average shot on Earth, wrote Robert Frost, an instructor and flight controller at NASA. Quora
Related: What would happen if you fired a gun into space?
The energy of an impact is not only related to the size of an object; speed (speed and direction) are equally important. That’s why a small bullet can do so much damage; when moving at a high enough speed, any object can be dangerous, Reddy told Live Science.
Keep in mind that speed is additive, said Kerri Cahoy, an associate professor of aeronautics and aerospace at the Massachusetts Institute of Technology. So if two objects move towards each other when they collide, that increases the energy of their impact.
“Think of it like driving on a highway,” Cahoy told Live Science. Two fast-moving cars heading in the same direction could hit each other and “barely kiss,” she said. But if a vehicle – even a lightweight one, such as a motorcycle – hits a car while driving in the opposite direction, it can be disastrous for both drivers.
Likewise, in space, a fast-moving speck of paint that collides with the ISS can leave a relatively large impression.
In space, satellites, spacecraft, and debris orbit many different paths; while one object can rotate horizontally around the equator, another can rotate vertically around the poles. Some objects even move “in retrograde,” meaning that they rotate against the Earth’s orbit. As more and more debris clogs space, Earth’s low orbit (in which the ISS orbits) turns into a busy highway during rush hour. “There can be a lot of damage,” Cahoy told Live Science.
The astronauts on board the ISS were lucky that a larger piece of debris did not hit their window. A fragment the size of a microbe can only leave a dent, but a fragment the size of a pea can disable critical flight systems, according to the European Space Agency. A piece of debris the size of a ping pong ball? “That would be disastrous,” said Reddy. At that size, space debris could quickly depressurize the space station, making it impossible for astronauts to breathe on board, Reddy said.
Space junk is a growing problem. Earth’s orbit contains at least 128 million pieces of debris, and 34,000 of them are larger than about 10 centimeters, according to the Natural History Museum in London – which are exactly the fragments large enough to detect. These smaller pieces are created when satellites naturally resist extreme ultraviolet radiation, when larger pieces of space debris collide, or when satellites are deliberately destroyed. Larger pieces include 3,000 decayed satellites, as well as bolts and other parts thrown off by spacecraft during launches.
By tracking space debris, scientists can tell countries and companies when to maneuver a spacecraft out of the path of a fast chunk of debris, Reddy said. According to the Natural History Museum, the ISS has performed 25 of these maneuvers since 1999. And researchers are developing ways to fish debris from space, such as using hooks, nets, and magnets to pull it back into Earth’s atmosphere.
Too much space debris can make it dangerous for humans to use Earth’s orbit for satellites and other types of spacecraft. We’re now a long way from that point, but it’s important to get ahead of the space problem to prevent further accumulation, Reddy said.
“We need space for so many things: communications, weather forecasting, banking, entertainment, and military,” he said. “In terms of our advancement as a civilization, we would take many steps backwards if we didn’t have access to space.”
Originally published on Live Science