This week, he turns his attention to our very own Red Planet - well, the planet Mars that is.
He is joined by an excellent panel of:
John Zarnecki, Professor of Space Science at the Open University and a team leader on the ExoMars mission
Colin Pillinger, Professor of Planetary Sciences at the Open University and leader of the Beagle 2 expedition to Mars
Monica Grady, Professor of Planetary and Space Sciences at the Open University and an expert on Martian meteorites
It's a very good programme -enjoy!