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. NASA come to Death Valley to test out their machines, so for Jonathan's ultimate test we subject his rover to a NASA style experiment in the desert. But unlike NASA, Jonathan has just three days and whatever he can find lying around the mine to come up with a working rover.

Staying with the theme of exploration, Iain and Ellen have to use their geological and botanical skills to search for water in the desert. Death Valley and the deserts around it are some of the driest places on the planet, so they're going to have their work cut out.

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 - an essential component for any mission into deep space. But just to make it a bit harder, not only are they going to have to purify it, they're going to have to make it taste good as well, because at the end of day three we're going to have a blind tasting. Kathy and Mike's purified water will be up against drinking water.

Jonathan's rover is based on a wooden chassis, supported by small bicycle wheels. It's powered by a couple of electric drills which he cannibalises and attaches directly to the front wheels. To steer it he changes the power going to each wheel. But the really clever bit is the remote control. He decides to control it by making a musical instrument, and sending the tones to the rover via walkie-talkie. Each different tone gives the rover a different instruction - forward, back, turn right or turn left.

Ellen and Iain aim to find water using the same principles that NASA use to search for water on other planets - they look for features in the landscape where water has left its mark. Iain spots a gully with signs of a recent flash flood, so they follow it in the hope that somewhere along its course water will have been trapped in the rocks or in the soil. Along the way Ellen finds plants which indicate that water isn't too far below the surface. And then they come across a tiny desert oasis - just a few straggly trees. But even though the soil is moist here, when they dig down they find that the damp layer isn't very thick. So Ellen sets up a solar still to evaporate water out of the soil. At the same time she wraps plastic sheets around a branch to collect the water that transpires off the leaves. Next day they have miraculously collected 2 small jars of rather mucky looking water. Not much for Kathy and Mike to purify. But on the way back to base Iain uses his geological knowledge to find one more source of water...

Kathy and Mike have a two pronged strategy for cleaning the water. Mike makes activated charcoal to filter out contaminants - it's exactly the same way that NASA clean water on the space shuttle. But to be extra safe Kathy makes a solar cooker to boil the water, to remove microscopic bugs that might have crept through the filters.