Cat and Bill are on the hunt for their next meal. Armed with primitive weapons, they follow the evolution of Homo Erectus from being hunted, to becoming the hunter. THE GREAT HUMAN RACE AIRS MONDAYS 10/9c.

“The caves themselves are very complex with hazards deep inside. The recipe is set for a cave rescue with a lot of dire consequences,” says Eduardo Cartaya, a National Geographic grantee who is leading an expedition into the ice caves inside one of Mount Rainier’s craters.

With a background in search and rescue, Cartaya hopes that his team’s data will help protect the thousands of people who attempt to climb Mount Rainier every year. Climbing any mountain presents inherent risks, but Rainier’s caves are especially dangerous since they have pockets of poisonous gases like carbon dioxide, sulfur dioxide, and hydrogen sulfide.

“These caves are being visited by recreational climbers who frequently take shelter inside the caves when they are caught on the summit by unexpected storms. We want them to know and understand that yes, there are hazards in there and to know where those hazards are so that they’re not trapped up there for 24 hours in a storm and find themselves in a pocket of bad air, because there wouldn’t be time to rescue them in a situation like that,” Cartaya explains.

Rescuing lost or injured climbers in the caves is a time- and resource-consuming operation, as Mount Rainier is very remote and hardly what you’d expect to find less than two hours from Seattle, Washington. “The crater of Mount Rainier is often referred to as the ‘backside of the moon.’ It actually used to be considered for a training ground for astronauts. And not only are we at the summit, we’re under the summit inside a glacier with active volcanic activity in it. It clearly couldn’t be more remote or, I guess, otherworldly or dangerous than that,” says Cartaya.

The uninviting, alien nature of the caves also draws many scientists to join Cartaya on the expedition. The unique environment offers the scientists an otherworldly laboratory to study how microbial alien life may exist on icy planets. “One of the amazing things about these caves is that they simulate what we might find on other planets or moons in the solar system. They are one of the few locations where you have a blend of volcanic gases mixing with a high altitude dark icy cave, which replicates a lot of what they expect to find in Europa, the Martian ice caps, or ice bodies somewhere in the solar system.”

Other researchers on the expedition are monitoring changes in the caves internal climate. Cartaya explains, “By measuring the ice walls of the cave year after year and noting whether they expand or contract could help us determine if the volcano is heating up, producing more steam, or if there’s any imminent volcanic activity in the future. That could be used to give early warnings if the volcano’s behavior starts to change. With Seattle and other cities nearby, that’s a pretty important thing to know.”

The climate data is also useful because glaciers are universally recognized as climate indicators. “The glacier caves on Mount Rainier circulate air from the atmosphere throughout the system and store records of the climate in the layers of ice. The work being done in the caves by researchers with Ruhr University is part of a worldwide study on the effects of climate on our ice packs and how caves contribute to the processes,” says Cartaya. “We hope to relate changes in the passage dimensions to either the effects of climate or the effects of the hydrothermal system of the volcano.”

Conducting the varied research in the caves poses many risks to the expedition team, but just walking on the mountain is an incredible challenge itself. In order to get to the caves, the expedition team must walk along Mount Rainier’s icy summit, which has an active volcanic crater just beneath, winds that can reach 140 miles an hour, and hidden crevices that empty into passages of toxic air.

With a seemingly endless supply of danger and the fate of 75 team members in his hands, the expedition definitely takes its toll on Cartaya. “When I come down after the expedition, it takes probably two months to wind down from the stress of it. The last thing I could bear is if one of my teammates was hurt or killed doing this project.” But Cartaya says that won’t keep the team from returning to the caves many times over: “The real value of scientific studies in places like this is not just one singular snapshot of data in one day, but to record change over a long period of time. That’s why we’re going to be going back up year after year,” says Cartaya before adding, “All I can say it’s probably one of the most exciting, stressful, and rewarding experience I’ve ever had in my life to do this.”

Click here to read more with Eduardo Cartaya: http://voices.nationalgeographic.com/2016/02/01/exploring-toxic-ice-caves-in-an-active-volcano/

Check out the adventures of other National Geographic grantees in the field by watching the rest of the Expedition Raw series: https://www.youtube.com/playlist?list=PLivjPDlt6ApQwXq3U8A7Y3HAWPajyXOIQ