Rosetta has travelled a distance of about seven billion kilometres. (Frame from 'Chasing A Comet – The Rosetta Mission'.) Chasing a Comet – The Rosetta Mission: www.youtube.com/watch?v=5b7u6stKgfs DLR Rosetta special: www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10394/ Credit: DLR (CC-BY 3.0)