The origin of Turkmenistan’s Darvaza Crater – nicknamed the “door to hell” – is disputed, but the theory most widely accepted involves a Soviet expedition to explore for gas.

A Turkmen geologist claims the borehole was set alight in 1971 after fears it was emitting poisonous gases. It has now been burning for 40 years.

Photograph: George Verschoor/National Geographic Channels Photograph: George Verschoor/National Geographic Channels

The crater, which is 69 metres wide and 30 metres deep, is located in a natural gas field in Ahal Province in Turkmenistan, which has the sixth largest reserves in the world.

George Kourounis, a Canadian explorer, became the first person known to have ventured into the pit last year, though footage of his expedition first aired this week on National Geographic, which partly funded the expedition. The aim was to collect soil samples from the bottom of the pit, to try to establish whether life can exist in such a harsh environment.

Photograph: George Verschoor/National Geographic Channels Photograph: George Verschoor/National Geographic Channels

“The story behind how [the crater] came into existence has been sort of shrouded in mystery, and there’s no other place like it on Earth,” Kourounis told National Geographic. “It is very unique, in that there’s no other place where there is this pit of burning methane that’s being ejected from the ground at high pressure”.

Photograph: George Verschoor/National Geographic Channels Photograph: George Verschoor/National Geographic Channels

The project took 18 months to plan. The team set up a rope-rigging system over a river gorge to practice lowering Kourounis in. He even had a Hollywood stunt expert set him on fire a few times, to “prepare myself for not panicking being up close around flame”.

Photograph: George Verschoor/National Geographic Channels Photograph: George Kourounis descends into the crater.

Kourounis admits he was a little nervous before the expedition.

“When you first set eyes on the crater, it’s like something out of a science fiction film,” he says. “You’ve got this vast, sprawling desert with almost nothing there, and then there’s this gaping, burning pit... The heat coming off of it is scorching.

“You have to shield your face with your hand just standing at the crater’s edge. Here I am thinking, ok , maybe I’ve bitten off a bit more than I can chew.”

Photograph: George Verschoor/National Geographic Channels Photograph: George Verschoor/National Geographic Channels

To withstand the intense heat, Kourounis wore special breathing apparatus, a heat-reflective suit, and a custom-made climbing harness made out of Kevlar so that it would not melt.

Photograph: George Verschoor/National Geographic Channels Photograph: George Verschoor/National Geographic Channels

The crater has become a minor tourist attraction in Turkmenistan, though Kourounis says he didn’t have any trouble with crowds of people turning up to watch him. Only a few “tourist outfits” and a couple of people with camels passed by.

“Once you’re there – if you can find the place – you can drive up, get out of your car, walk over to the edge, and jump right in, if you want,” he says. “The choice is yours. And I’m so far the only person who has actually done that”.

Photograph: George Verschoor/National Geographic Channels Photograph: George Verschoor/National Geographic Channels

Kourounis compared his experience of descending into the pit with what it might feel like to land on another planet. He describes it as a “coliseum of fire” made up of thousands of small flames, which together sound as loud as a jet engine.

Photograph: George Verschoor/National Geographic Channels Photograph: George Verschoor/National Geographic Channels

“You feel very, very small and very vulnerable in a place like that,” says Kourounis.

Kourounis and the team were happy with the results of their expedition, and believe it may even help to inform potential space missions in the future searching for signs of life outside of our solar system.

“We did find some bacteria living at the bottom that are very comfortable living in those high temperatures, and the most important thing was that they were not found in any of the surrounding soil outside of the crater,” he says. “Outside of our solar system, there are planets that do resemble the conditions inside this pit, and [knowing that] can help us expand the number of places where we can confidently start looking for life outside of our solar system.”

Photograph: George Verschoor/National Geographic Channels Photograph: George Verschoor/National Geographic Channels

Turkmenistan is one of the most isolated countries in the world, yet its fledgling tourism industry hopes to capitalise on crater as an attraction for thrillseekers. Because it’s not fenced off, visitors can stand right on the edge of the crater, despite the safety hazards.