Nasa's Messenger probe 'had to crash-land'
Nasa's Messenger mission to Mercury has reached its explosive conclusion, after 10 years in space and four in orbit.
The Messenger probe crash-landed on the surface of Mercury at 12-times the speed of sound - and it was no accident.
Larry Nittler the deputy principal investigator on the mission - whose job it is to sift through all the data sent by the probe - told the BBC's Katty Kay why the probe had to crash-land and what Messenger had taught scientists about Mercury.
01 May 2015