A piece of “space debris” that hit the International Space Station chipped the outer layer of a window in the spacecraft's observation module.
British astronaut Tim Peake posted a picture on Twitter Friday showing the damage, a chip about 7 millimeters in diameter that hit one of the seven windows in the "cupola" observation area.
“Often asked if @Space_Station is hit by space debris. Yes – this chip is in a Cupola window,” he tweeted.
Whatever chipped the window apparently was quite small, but the European Space Agency said a larger object would pose a “serious threat” to the station's safety.
The observation area windows give astronauts a panoramic view of the station's exterior, and are used during docking, spacewalks and other delicate maneuvers. They include the largest panes of glass ever installed in a spacecraft, measuring 80 centimeters.
According to NASA, space station windows are comprised of four panes of glass, each between 1.2 and 3.2 centimeters thick. Should a piece of debris break through the windows, NASA said aluminum shutters should snap into place to protect the occupants.
British astronaut Tim Peake, a member of the main crew of the International Space Station, waves to his children from a bus prior the launch of Soyuz TMA-19M space ship, at the Russian leased Baikonur cosmodrome, Kazakhstan, Dec. 15, 2015.
“An object up to 1 cm in size could disable an instrument or a critical flight system on a satellite,” ESA said in a news release.
“Anything above 1 cm could penetrate the shields of the station’s crew modules, and anything larger than 10 cm could shatter a satellite or spacecraft into pieces.”