A hole in Canadarm2, the station's 60-foot robotic arm
used to ferry payloads and perform maintenance on the station, was discovered during a routine inspection of the International Space Station
A fast-moving piece of space junk
was the culprit.
The hole was punched through a thermal blanket wrapped around the arm boom, according to the Canadian Space Agency
After what CSA officials called a "lucky strike," the arm's performance was unaffected.
We'll never know what caused the damage, but NASA estimates that there are 100 million pieces of debris larger than one millimeter in low Earth orbit.
While the size of those objects is relatively small, their speed of up to 17,500 mph – more than eight times faster than an AR-15 bullet – means that even a small piece of junk can cause significant damage, and the space station itself is moving at roughly the same speed, so a head-on collision poses a significant risk.
A number of space shuttle windows, for example, had to be replaced due to damage caused by paint flecks in space; in 2016, a possible paint flake struck a window in the Cupola of the space station, gouging out a 7 mm chip, as documented by European Space Agency astronaut Tim Peake.
“I am frequently asked if the International Space Station is hit by space debris,” Peake explained at the time, adding, “Yes – this is the chip in one of our Cupola windows, glad it is quadruple glazed!”
Yes – this chip is in a Cupola window https://t.co/iH87Dt80yV
pic.twitter.com/7ZvVs4myM0 — Tim Peake (@astro_timpeake) May 12, 2016
NASA tracks approximately 23,000 pieces larger than a softball and capable of causing major damage out of the 100 million pieces of space trash tracked.