NASA astronaut Jasmin Moghbeli looked out of the large windows on the International Space Station on Monday afternoon and saw that it was snowing in space.

Well, not really snowing. But there were flakes flying by that looked a lot like flurries. They emanated from one of two radiators that service the “Nauka” science module attached to the Russian segment of the space station. The flakes were frozen coolant, and as a protective measure she and other crew members on the orbiting laboratory closed the shutters on the US segment windows.

Moghbeli and the other crew members were never in any real danger from the radiator leak, but the problem does raise serious concerns about the viability of Russian hardware in space. That is because this is the third such leak that has occurred with Russian equipment in less than a year.