The European Space Agency's comet-chasing Rosetta mission was launched in 2004, before social media became a popular tool for mainstream communication. As it reached its destination ten years later, new audiences were reached and inspired by this once-in-a-lifetime event by harnessing a range of outlets for communicating the key messages. These included traditional online plat forms, such as news websites, blogs, and Livestream, as well as Twitter, Facebook, Instagram, Flickr, YouTube, Google+ and SoundCloud. In this article, we outline the role social media channels played in making Rosetta one of the European Space Agency's biggest communication and public engagement successes. [ABSTRACT FROM AUTHOR]