(Scroll down to the bottom if you want to skip the context to see the answer)
By 2022, the European Space Agency hopes to send a probe to Europa, one of Jupiter's 63 moons.
Europa is special because two years ago a plume of water vapour was observed above its south pole by the Hubble telescope.
The excellently-named Juice (Jupiter Icy Moons Explorer) will spend three and a half years (after a seven-year journey) trying to discover whether there are oceans hidden in the Jovian system.
Not to be outdone, Nasa also has a separate mission to Europa, which it considers one of the "most promising places in the solar system to search for signs of present-day life".
The mission is so official that it has its own Twitter account, which last week posed this (surprisingly difficult) question.
The answer? This is Europa (middle row, left), in all its majesty.