“A piece of space debris too small to be tracked has hit and damaged part of the International Space Station - namely, the Canadarm2 robotic arm.”
Over 23,000 pieces of junk are tracked in low orbit, and all of them are softball-sized or bigger. Everything smaller is invisible until it hits something. This one punched through the arm’s thermal blanket. Last year the ISS had to dodge debris three times, and the pile keeps growing.