Once upon a time there was a space probe called Rosetta, which was shot into the night sky. She was embarking on a long, long, journey with the aim of unveiling the secrets of our solar system. On board was her constant companion, the lander Philae. The destination of their journey was comet 67P/Churyumov-Gerasimenko. On the long journey from Earth into space, you'll hear from Rosetta and Philae about what it takes to explore a comet up close. You'll also find out what can be learned about comets, these "dirty snowballs" in space.