Much of this apparent “snow” wouldn’t actually be visible if you were standing on 67P’s surface. It is made of cosmic rays – charged subatomic particles that flit across the universe. As they hit the camera’s sensors, they register as streaks of light.
Some of bright specks are actually snow – dust and ice particles floating above the comet’s surface. And many of them are stars behind the rocky cliffside on 67P’s surface.
