How to remember to forget - the new science of erasing memories; Big, old and banged-up - Canada is home to the world's largest Tyrannosaurus Rex; A woman who can smell Parkinson's disease could hold the key to early diagnosis; Meet the odd little moons that interact with Saturn's spectacular rings; Google glasses could help kids with autism read emotional cues in people's faces; What would happen if the Yellowstone supervolcano exploded?