As the old saying goes, life can move pretty fast, but this is especially true in space, where the difference in orbital velocities between two different objects can literally be faster than a speeding bullet. Last month, British astronaut Tim Peake posted a photograph of a 7 mm (1/4 inch) impact chip in one of the International Space Station’s Cupola windows, suspected to have been caused by a miniscule piece of debris no bigger than a few thousandths of a millimeter across.

“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!” Peake remarked on Twitter. Installed in 2010, ISS’s Cupola is a seven-windowed observational module that offers the station’s crew a 180-degree view of the Earth and space, enabling them to remote-control equipment from inside the ISS, make scientific observations of the planet below, or to just enjoy the spectacular view.

Built by the ESA, the module is built to withstand impacts like this, made of fused-silica and borosilicate-glass windows, with closeable shutters that can provide extra protection if needed. The rest of the ISS was also built with impacts like this in mind, with extensive shielding installed in vital areas, since even tiny objects the size of a grain of sand can be moving fast enough to cause extensive damage.

When it comes to larger debris, mission planners will adjust the orbit of spacecraft like the ISS to avoid impacts: over 21,000 pieces of orbital debris over 10 cm (4 inches) are actively tracked for such purposes, and there are an estimated 500,000 pieces of debris between 1 and 10 cm zinging about. A 3D visual representation of this steadily growing problem can be seen at Stuff in Space, a real-time mapping of all of the manmade objects in orbit, both active and discarded. 

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