Out of all the things that you don't want to see while revolving around the Earth in a pressure-sealed environment like the International Space Station, the scenario in the image above undoubtedly tops the list. This quarter-inch (7-mm) diameter mark in one of the windows of the Cupola - that small corner where astronauts generally take all their stunning pictures - was snapped by British astronaut Tim Peake this week against an inky backdrop of space.
Peake in a European Space Agency (ESA) release, said "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!"
The good news is that this particular chip isn't a huge deal, and it's not that uncommon. It was most likely produced by the impact of a small piece of space debris, as ESA writes: "possibly a paint flake or small metal fragment no bigger than a few thousandths of a millimetre across,"
Although this piece of a space debris was tiny, but with the ISS continually falling towards Earth at a mind-boggling 7.66 km/s (4.7 mps), even the tiny specks of paint can have a big impact.
The good thing is that the space station is aimed to handle these sorts of small scrapes and nicks. All the windows on ISS are made from fused-silica and borosilicate-glass, and wide-range shielding around all the astronauts and technical areas.
According to ESA, an object up to 1 cm in size can damage an instrument or a critical flight system on a satellite. Anything larger than 1 cm could breach the shields of the Station’s crew modules, and anything larger than 10 cm could easily break a satellite or spacecraft into pieces.
To counter this threat, NASA and the ESA are persistently improving their debris-mitigation strategies. Part of that includes observing space junk above 1 cm in size so that they can calculate the risk of impact and direct the ISS out of harm's way if required.