Of all the things you don't want to see while orbiting Earth in a pressure-sealed habitat like the International Space Station, the view in the image above probably tops the list.
This quarter-inch (7-mm) diameter chip in one of the windows of the Cupola - that little nook where astronauts take all their cool pictures - was photographed by British astronaut Tim Peake this week against an inky backdrop of space. And holy crap, we'd be freaking out right now.
"I am often asked if the International Space Station is hit by space debris. Yes - this is the chip in one of our Cupola windows, glad it is quadruple glazed!" said Peake in a European Space Agency (ESA) release.
The good news is that the chip isn't a big deal, and it's not that unusual. It was most likely caused by the impact of a tiny piece of space debris, "possibly a paint flake or small metal fragment no bigger than a few thousandths of a millimetre across," writes the ESA.
It's crazy to think that such tiny, insignificant objects can do this much damage, but with the ISS constantly falling towards Earth at a mind-boggling 7.66 km/s (4.7 mps), even tiny flecks of paint can have a big impact.
Luckily the space station is designed to handle these types of small scrapes and nicks, with all its windows made from fused-silica and borosilicate-glass, and extensive shielding around all the crew and technical areas.
But if the ISS got hit by anything bigger, it could be in big trouble, as the ESA notes:
"An object up to 1 cm in size could disable an instrument or a critical flight system on a satellite. 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."
Umm... Gravity, anyone?
To counter this risk, NASA and the ESA are constantly improving their debris-mitigation guidelines. Part of that involves monitoring space junk above 1 cm in size so that they can predict the risk of impact and steer the ISS our of harm's way if need be.
But they're also trying to cut down on space junk in the first place, and the ESA has made it mandatory for all of their mission parts to reenter the atmosphere and burn up within 25 years after they're retired.
That's a great plan, but with all this space junk out there already, a back-up definitely doesn't go astray... sometimes it's easy to forget how scary space can be.
Sources: Science Alert, Gizmodo