CO2 and rice, Underground farming, Ancient interstellar asteroid, Microplastics air pollution

New research suggests that rice will be depleted in important B vitamins and minerals by rising CO2 levels in the atmosphere. Adam Rutherford to talks to Kristie Ebi of the University of Washington, one of the scientists behind the finding, and consults Marco Springmann of the Future of Food project at the University of Oxford. Is the future of farming subterranean? Marnie Chesterton visits a farm called Growing Underground for some answers. Specialising in salad and herbs, it is located beneath Clapham Common in South London in an old Second World War air-raid shelter. Has an interstellar asteroid been lurking in our solar system for more than four billions years? It's a possibility according to the astronomers who've watched and plotted its strange orbit. It travels around the Sun in the opposite direction to most of the planets, asteroids and comets. Asteroid specialist Alan Fitzsimmons of Queens University Belfast talks to Adam about this astronomical oddity and assesses the evidence for it being a traveller from the stars, captured by our solar system during its early childhood. Stephanie Wright of Kings College London explains about what we do and don't know about the abundance and health risks of microplastic particles in the air we breathe. Producer: Andrew Luck-Baker.