Space Junk Hit a Robotic Arm on the International Space Station

The arm, called Canadarm2, remains functional and will continue with its next mission

Two photos show the robotic arm with Earth in the background, and a close-up shows the small hole in the white thermal blanket on the arm
A tiny piece of orbiting debris punched a five-millimeter-wide hole in the robotic arm's insulation. Courtesy of the Canadian Space Agency

On May 12, a routine inspection of a robotic arm on the International Space Station revealed a five-millimeter-wide hole in its thermal covering.

According to a statement by the Canadian Space Agency, the robotic arm known as Canadarm2 collided with a small piece of orbital debris—also known as space junk. The exact object that punched a hole in the robotic arm is unknown. Because the object only damaged the thermal blanket of the arm boom, and not a piece of electronics or machinery, the arm will continue to carry out its planned missions, Ashley Strickland reports for CNN.

"The threat of collisions is taken very seriously. NASA has a long-standing set of guidelines to ensure the safety of Station crew," says the Canadian Space Agency in its statement. "The safety of astronauts on board the orbiting laboratory remains the top priority of all Station partners."

Earth is surrounded by orbiting debris: about 8,000 metric tons of it, as of January 1, 2020, reported Elizabeth Gamillo for Smithsonian in January. The U.S. Space Surveillance Network tracks about 23,000 objects that are larger than the size of a softball, writes Elizabeth Howell for Space.com. But there are tens of millions of pieces of debris smaller than a centimeter wide that are too small to be monitored.

The small hole in the robotic arm is a reminder of the danger that space junk presents to astronauts.

“There’s a lot of stuff out there traveling at over 17,500 mph and obviously it can do a lot of damage,” says University of Buffalo aerospace engineer John Crassidis to Richard Luscombe at the Guardian. “This one didn’t do any real damage, it went through some insulation and we don’t even know if it hit part of the arm. [But] it’s some pretty scary stuff.”

Tiny debris like whatever damaged the robotic arm can include micrometeorites, dust particles and flecks of paint from satellites. Moving at thousands of miles per hour, very small pieces of debris can cause serious damage. NASA had to replace the windows of space shuttles after impacts with paint flecks, the Guardian reports.

Because the Canadarm2 escaped this collision without damage to vital components, it will move forward with its next mission, using its robotic hand to replace a faulty power switchbox, per Space.com. The space agencies will continue to analyze the damage and determine whether it affected the arm’s performance.

Since 1999, the ISS has had to perform 26 special maneuvers to avoid collisions with space junk, including a maneuver performed in September 2020. Engineers today are coming up with solutions both to avoid creating future space junk—like by creating wooden satellites—and to clean up the space junk already orbiting Earth. One recent attempt to clean up outer space is a spacecraft that attaches to dead satellites and pushes them toward Earth so that they fall out of orbit and burn up in the atmosphere, Chloee Weiner reports for NPR.

“The biggest thing we worry about is the astronauts,” says Crassidis to the Guardian. “They’re very exposed out there, and some day it’s going to be a question of when, not if.”