Week one's challenges are heavily focused on the "exploration" theme. Jonathan's challenge is to make a rover; a remote controlled vehicle that could explore strange new worlds. Staying with the theme of exploration, Iain and Ellen have to use their geological and botanical skills to search for water in the desert. Assuming they find some water, Kathy and Mike are going to have to find a way of purifying it to make it safe for drinking and they're going to have to make it taste good as well, because at the end of day three Kathy and Mike's purified water will be up against drinking water.

• Kate Humble
• Iain Stewart