George Kourounis has chased tornadoes across the American Midwest, swam with piranhas in Venezuela and even got married on a crater of an erupting volcano in the South Pacific. The explorer and adventurer has had many incredible experiences in nature's extreme environments. But a recent trek to a distant part of the Central Asian country Turkmenistan may be one of his most exciting expeditions. Kourounis was the first individual to descend into a 30-meter (100-foot) deep pit of fire known as the "Door to Hell." It's a crater in a large natural gas field that has been burning for decades. It is said that an old Russian oil rig fell into the crater in 1971. Geologists were worried the pit was releasing poisonous gases, and so decided to set the pit on fire. The scientists thought the gas would burn off quickly. They were wrong, and the resulting gas-fed flames continue burning to this day. Kourounis and his team were unable to confirm the story behind the pit, but they definitely confirmed that the site exists and that it's one of a kind. The Canadian adventurer and former host of TV's "Angry Planet" had wanted to visit the Door to Hell for years. "Every now and then, I would look at pictures on the Internet of the place again, and it just never exited my mind," Kourounis says. Burning Challenges And Bureaucracy One might think that descending into a burning pit would be the main challenge of this expedition. However, Kourounis notes that his crew met another major difficulty earlier on. "The biggest goal was just getting permission to get into the country," he says. Turkmenistan is one of the hardest countries in the world to visit. The government does not allow many people in or out. The crew finally gained entry into Turkmenistan in 2013 after two years. Kourounis says the crater, which is about 76 meter (250 feet) wide, looks like a volcano in the middle of the desert. "It is burning with a tremendous amount of flame like there is a lot of fire down there," he says. "Day or night, it is clearly burning. You can hear the roar of the fire if you stand at the edge." He added that being near the heat is unbearable. "There are thousands of little flames all around the edges and toward the center. Then there are two large flames in the middle at the bottom," he says, probably where natural gas used to be drilled for. Before going into the burning pit, Kourounis got his equipment in order. This included a custom-made climbing harness made out of Kevlar, a self-contained breathing apparatus (similar to scuba gear), fire-resistant ropes and an otherworldly heat-resistant suit. The suits, which look like aluminum foil and reflect radiant heat, are used by some firefighters and steel-mill workers. Kourounis still got pretty hot inside his gear. He said he felt a bit like a baked potato wrapped in his foil suit. Another very specialized piece of equipment that Kourounis brought to Turkmenistan was a heat probe. It was designed by the engineers who build National Geographic's Crittercams. "It sort of looks like a sword," Kourounis says. He would spear the ground and get a reading of its temperature. The probe could then wirelessly transmit the temperature of where he was. Entering The Door To Hell Even after a few days of preparing, Kourounis says the idea of actually descending into the Door to Hell was nerve-wracking. "I can tell you when you are standing on the edge of this gigantic crater filled with fire — it is intimidating," he says. Still, the adventurer did descend into the fiery hole. "It wasn't dark at all," Kourounis says of the crater's interior. "As a matter of fact, you are surrounded by flames, so everything has this orange hue." Once on the floor of the pit, Kourounis embarked on the scientific core of the expedition. The most important part of the mission was to take some samples of the soil and sand at the bottom. From this, they would see if there were any tiny bacteria living at the bottom. These life forms could provide clues about life in these extreme environments, Kourounis says. He added, "There are planets that have been discovered outside of our solar system that have a very hot, methane-rich environment kind of similar to what is in the crater." Basically, he said, they "were looking for alien life right here on Earth." The soil samples were given to Dr. Stefan Green, the microbiologist on the expedition, studying tiny life forms. Green says that a few kinds of bacteria were discovered in the soil from the crater floor. These microorganisms are known as extremophiles because they can survive in extreme environmental conditions. Extremophiles survive in incredibly hot, cold, salty, acidic or dry conditions. The ones at the Door to Hell appear to be "enriched" by the high temperature and low nutrient levels, among other things, says Green. Along with this discovery of unexpected life in one of the Earth's most inhospitable places, the Door to Hell has an out-of-this-world feel to it, according to Kourounis. "The orange glow from the flames makes the ground completely orange, and the walls of the crater look orange," he says. "It really reminds me of being on a place like Mars, where you have that orange or red soil."