A 7mm chip has appeared in one of the windows of the International Space Station; but it’s not just any window, it’s the large Cupola that the European Space Agency added to the International Space Station in 2010, and it provides the best view of the Earth of any window in the International Space Station to date.
So what caused the chip? Well as it turns out, there is a lot of space junk orbiting the Earth from expired space missions, as well as small rocks and debris. It just so happened that one of those pieces of junk was right in line with the path of the International Space Station, and the Cupola window just happened to be facing the point of impact.
Space junk hits the International Space Station very often, but NASA is careful to make sure no satellites or larger space equipment come into contact with it. It’s not every day, on the other hand, that windows get chipped by it.
Fortunately, the window of the Cupola is quadruple glazed, as ESA astronaut Tim Peake said in a statement. The thick multiple-layered fused-silica and borosilicate-glass windows take a lot more than whatever hit it to smash through.
The glass is strengthened even more-so than that of bulletproof glass, and it needs to be. Space junk travels as fast as 18,000 miles per hour, which is a lot considering the average bullet travels at 1,700 miles per hour. Combining that statistic with just how much space junk there is out there, it’s not hard to understand why it poses such a risk, especially on space walks.
The following video, shared by NASA a couple of years ago, simulates just how much space junk orbits the Earth at one given time.
We know, it’s kind of hard to believe, but the International Space Station is rarely ever damaged by any of that stuff.
As it sits right now, the chip is nothing to be worried about. There is no chance of the chip growing and spidering. The Cupola window likely will not be replaced, as it doesn't need to be because of all the protective layers of glass.
Source: ESA