Has there been any space mission to Mercury?

There were 2 space probes sent to orbit Mercury: Mariner 10 and Messenger. Both attained orbit and sent back information about the planet to Earth. Mariner 10 ran out of energy to send back signals to Earth, but, it is probably still in orbit. Messenger began it's mission earlier in 2011 and is still working, sending information back to Earth. Since rocket power would be needed to land a spacecraft on Mercury, (the planet has almost no atmosphere), there are no plans to land a vehicle on the planet, as it would take too much fuel than we can afford to put into spacecraft at this time. It's too expensive to send an unmanned vehicle that can safety land on Mercury. It's far too dangerous to send humans to Mercury and it will probably never, ever happen in the future.