The series begins in Iceland, where scientists are drilling into an active volcano.
Probing the crater left by the asteroid that killed off the dinosaurs.
The sediments beneath the ocean floor were long thought to be a virtual desert, devoid of life.
Gabrielle examines core samples from 500 metres under the Pacific which suggest that more than 10% of life on Earth lives out a long, slow, but high-pressure existence there.
How space scientists are drilling for aliens! This is not on a distant planet (yet), but in a very strange, wine-red river system in Spain that could reflect the last refuge for life on Mars.
Gabrielle examines an ice core from the middle of Antarctica that reveals how world climate has changed over the last 800,000 years.
It's amazing what you can find in a hole in the ground, so Gabrielle Walker sets out to investigate.