The Mars Exploration Rover, better known as Opportunity, has been beaming back images and data from our planetary neighbour since 2004. As as of today, it has travelled 26.219, making it the first little interplanetary explorer to complete a marathon.
Although that's not exactly a barnstorming pace — about 10m per day, or 3km per year — it's a pretty good job, considering the rover's primary mission was only three months long. It's even managed to outlast its rover sibling, Spirit, which soldiered on until it became a 'static research station' in 2010. (Read: it stopped moving.)
Opportunity isn't quite dead yet, but it's starting to show signs of old age. Faulty memory is causing data storage problems, and while it's not a terminal fault (RAM can be used to store information as a stop-gap measure), project lead John Callas isn't exactly optimistic about the future:
"It's like you have an ageing parent, that is otherwise in good health - maybe they go for a little jog every day, play tennis each day - but you never know, they could have a massive stroke right in the middle of the night. So we're always cautious that something could happen."
Mind you, if my ageing parents could run a marathon, maybe I wouldn't be quite so worried. [NASA]