Blue Peter is green and extreme this week. Lindsey and Radzi find out about real horse power when they try their hand at extreme carriage racing. Plus, Lindsey takes on an eco-challenge to find out the astonishing effect just a few days' waste can have on the environment. Back in the studio, the team demonstrate how to make a 'tin face toy' using recycled materials, and science daredevil Greg Foot creates his very own comet as he chats about the comet-chasing spacecraft, Rosetta!