Nearly 30 scientists and instrument specialists venture deep below for the fifth Mine Analogue Research sortie at the Boulby mine in northeast England.
Preparations for the expedition and sample collection follow strict protocols that could one day be replicated on other planets. Some of the activities are very similar to training for a spacewalk: there is isolation, complete darkness and the need to communicate efficiently with the rest of the team.
They use life-detection equipment, drills and cameras for robotic and human exploration.