BBC R4 Five Holes in the Ground

It's amazing what you can find down a hole in the ground. In this series of short programmes, Gabrielle Walker meets scientists who are drilling into a volcano for energy, drilling into a crater to discover what killed the dinosaurs, drilling into the sea floor to discover very ancient life, drilling into a river system in Spain in search of alien life and drilling into the centre of Antarctica to discover a climate record 800,000 years old.

Ep 01 Drilling for Heat

Geologists in Iceland are drilling directly into an active volcano! They've done so many times before, but never as deep as this. Iceland lies on the mid-Atlantic ridge, where new ocean crust is formed as the continents on either side move apart. So it is an exciting place geologically. Water circulates through the rocks, so, if it is pumped up from boreholes, it can be used to drive the turbines in power stations. That is done already and hot waste water provides one of Iceland 's biggest tourist attractions, the Blue Lagoon. But the drill team are now going deeper. They hope to reach more than 4000 metres down to where they expect to encounter so-called supercritical steam. This should deliver much more energy - five to ten times as much in fact, and could make Iceland an net exporter of energy.

Ep 02 Drilling for Dinosaurs

Around 65 million years ago, the dinosaurs became extinct, together with more than half of all species on Earth. Something catastrophic must have happened and geologists have traced debris from every continent back to a giant crater beneath the Yucatan peninsular in Mexico. They believe it was the result of an impact from an asteroid the size of Mount Everest. Researchers have been drilling into the crater to discover just what happened. They now believe that the impact blasted a crater more than 10 kilometres deep and nearly 200 kilometres across, melting more rock than there is water in the North Sea. It resulted in global forest fires, acid rain and several cold dark years followed by global warming which lasted centuries. The dinosaurs didn't stand a chance.

Ep 03 Drilling for Life

20 years ago, few believed John Parkes, now at Cardiff University, when he claimed to have grown living bacteria from sediment samples taken from 80 metres beneath the deep ocean floor. Now, new cores have been drilled off the coast of Peru specifically to search for buried life. The evidence suggests that more than 10% of all life on Earth is buried under the seabed. The Cardiff team are growing the bacteria in special pressure vessels and reveal their first results. Life at such depths is very slow, with a generation lasting 100,000 years, but this deep biosphere may go back many millions of years and could give clues as to where the first life on Earth took shelter.

Ep 04 Drilling for Aliens

The waters of the Rio Tinto in southwest Spain run red. The colour is due to metals dissolved by water made highly acidic by bacteria living underground. The latest results from rovers on the planet Mars suggests that that planet may once have run with similar acid waters. So astrobiologists from Spain and the US space agency NASA have teamed up for MARTE, the Mars Analogue Rio Tinto Experiment. They've been using a prototype drill of a sort that may one day be flown to Mars on a robot probe to search for Martian life.

Ep 05 Drilling for Climate

Dome C in the middle of Antarctica is a desolate place. The word 'white' is often used by people who have been there. It is also a very special place since the ice there is more than three kilometres thick. Trapped within it are tiny bubbles of ancient air going back 800,000 years through the ice ages. In a laboratory in Grenoble, glaciologists are analysing those bubbles to discover how closely the Earth's climate has followed changing carbon dioxide levels.