The mission: Travel more than 600 miles across the Arctic Ocean, in temperatures down to 40 degrees below zero.
It's the Catlin Arctic Survey, a British expedition to the North Pole. Its goal is to collect data to help scientists determine how fast the sea ice is disappearing.
Pen Hadow is the exhibition leader of a three-person team. It's Day 35, and the team is about 450 miles away from the North Pole.
The polar explorers are using equipment ranging from a mobile radar unit to good, old-fashioned clipboards and drills to record accurate measurements of ice thickness.
One of the challenges is the whipping northerly winds — it's pushing the ice back as the team walks forward, creating a treadmill effect.
"When we camp, sometimes we go backward half the distance that we traveled the previous day," Hadow says, "which eats away at your confidence and morale — but we are a tough crew and we are used to that."
As the temperature warms up, the ice will break into smaller pieces — and in a few weeks, Hadow says, the crew will have to swim between solid ice shelves and freezing ocean waters.
"A bit like James Bond when he gets in his special suit," he says. "We will lower ourselves into the water and swim to the next piece of ice."
If Arctic dips and moving ice caps don't seem like enough of a pain, Hadow adds that the polar chill "takes a tremendous hammering on your teeth."
Early in the expedition, Hadow bit into a chocolate bar, finding it hard as iron. "I wasn't concentrating and three quarters of the tooth chipped away," he says. "It's very difficult to do dental work up here."