Ryan MacDonald is one of 100 candidates for the Mars One project, that hopes to set up a human community on Mars. If it all goes to plan, Ryan will be leaving Earth in 2031 - and never coming back! We call up Ryan to find out more about his ambitions.

We also learn about some of the sea life that was alive in the age of the dinosaurs, meet a tiny creature with a big sting and wonder if humans could turn ever invisible - and whether that's a good idea or not!