The Messenger probe arrived in orbit around Mercury in March 2011, after a 7 year journey to the innermost planet in our Solar System. It mapped the entire surface of this tiny planet, of which we’d seen less than half from the previous mission back in the 1970s. Far from being a dry, inert ball of rock, Messenger has showed that the surface of Mercury has been changing in the very recent past (where “recent”, to a planetary scientist, means tens of millions of years). But what goes up, must come down, and on 30th April 2015 the Messenger probe crashed into the surface of Mercury.

Professor Dave Rothery is a planetary scientist at the Open University, and a member of the Bepi Columbo mission, which will launch in a few years to arrive at Mercury in a decade’s time. In this month’s programme, Dave describes the mysteries that Messenger has solved, but also those that remain for Bepi Columbo to solve.

Originally broadcast (in edited form) on 30th April 2015 as part of Pythagoras’ Trousers on Radio Cardiff.