Rough Science

In the first set of gold-mining challenges in New Zealand's Westland National Park, Ellen, Mike B and Mike L attempt to pan gold from a river while Jonathan builds a metal detector and Kathy devises a balance scale capable of weighing tiny amounts of gold to the nearest millionth of a gram.

Mike L, Kathy and Jonathan are set the task of building an automated gold-panning machine, while Ellen is challenged to work out the date of the most recent major earthquake in the area. The team's resident chemist Mike B is charged with the task of creating a skin-cream to help protect the scientists' hands in the cold New Zealand winter. And Kate reveals to the team their ultimate goal for the series.

Ellen's task this week is to devise a way of waterproofing a tent that Mike B and Mike L will take on an expedition to seek out gold. Meanwhile Kathy and Jonathan build a seismograph using parts from an old alarm clock.

The entire team are taken on a journey to the Franz Josef glacier and must pool their knowledge to work out both how fast the glacier is moving, and how fast it is melting. They must also create heat to keep themselves warm - but without lighting a fire.

With the team's time in New Zealand running out, Kate offers the team some extra gold to help them make their jewelery. But it's buried somewhere on a nearby mountainside - so the scientists will need cunning to work out exactly where. Meanwhile Kathy searches for gold on a beach, and the two Mikes work out how to extract the gold from rocks collected earlier in the series.

The culmination of the group's New Zealand adventure. The team have found enough gold to carry out their final task, but they still face the challenge of purifying the gold and working it into a piece of jewelery.