Does the distant dwarf planet Pluto have an ocean beneath its thick crust of ice? It's certainly possible, according to a group of researchers who are analysing the data from the New Horizons Pluto flyby last year. They argue that a deep ocean of water would best explain the position of the great heart shaped depression on Pluto's surface. Adam Rutherford quizzes planetary scientist Francis Nimmo about this new hypothesis.

Adam also talks to glaciologist Robert Mulvaney of the British Antarctic Survey, who is now setting off for the frozen south to prospect for the oldest ice in Antarctica. He's part of a European project which aims to drill deep into the ice sheet of East Antarctica and chart the climate and atmosphere history of Antarctica back to 1.5 million years ago.

Are grass-fed cattle better for the global climate than cattle fed on grain-based feeds? Dr Tara Garnett of the Food Climate Research Network at Oxford University responds to listeners comments on carbon emissions and diet.

Swifts can fly for 10 months non-stop, never touching the ground. Anders Hedenstrom of Lund University discovered this remarkable fact by fitting birds with a tiny electronic backpack which recorded their location and flight activity across a whole year.