Nasa Mercury Messenger team excited by orbit
16 March 2011 Last updated at 15:49 GMT
Nasa's Messenger spacecraft has arrived in orbit around Mercury, the innermost planet in our Solar System.
Previous missions have only performed flypasts, but Messenger will be the first to circle the rocky little world.
Mission chief Sean Solomon told the BBC the planet was "extreme in several respects", and "really pushes the level of our understanding".
He said that as the project had been in the planning for 15 years, "to say the science team is excited... is a huge understatement".