In this edition of The Naked Scientists: Evidence of a carbon cycle on Mars has been unearthed by the Curiosity rover. What does it mean for the red planet's past habitability? Also, the cannabis-based painkiller as powerful as an opioid, but without the side effects. And, could fashion sense and a primitive sunscreen have been the deciding 'factor 50' which allowed us humans to outlast the Neanderthals... Like this podcast? Please help us by supporting the Naked Scientists