Of all the amazing sights one might see on the ISS– stars, planets, comets and more– one thing you don't want to see is a crack in the window.

But that's exactly what a recent tweet from European Space Agency (ESA) astronaut Tim Peake showed: an impact chip in a window on Cupola, an observation and work area where the astronauts operate the robotic arms on the station. Understandably, it's since gone viral.

The photo, which was taken last month, was Peake's response to the oft-asked question of whether the ISS ever gets hit by space debris.

According to the ESA, the chip is 7 millimeters, or just over a quarter of an inch, in diameter. The culprit behind the chip? Believe it or not, ESA believes it was "gouged out by the impact from a tiny space debris, possibly a paint flake or a small metal fragment no bigger than a few thousandths of a millimeter across."

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That's a lot of impact for such a tiny speck.

"An object up to 1 cm (0.4 inches) in size could disable an instrument or a critical flight system on a satellite," the ESA writes. "Anything above 1 cm could penetrate the shields of the Station's crew modules, and anything larger than 10 cm (4 inches) could shatter a satellite or spacecraft into pieces."

Luckily, the ESA and ISS crew take extra careful measures to prevent debris from harming the station. Not only is there extra shielding but also responsibly disposing of waste and satellites that are no longer operational.

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