The journey to Mount Ortorten in Russia's Ural Mountains was supposed to take the hiking group a few weeks. They had no reason to expect otherwise: Most of the party's college-aged members, led by 23-year-old Igor Dyatlov, were experienced skiers and hikers. After completing the journey through the mountainous wilderness, they would have qualified for the highest hiking certification granted in the Soviet Union.

But the hikers never reached their destination. In February 1959, they went missing.

Searchers found the first bodies—the remains of five of the hikers—a few weeks later. They were in a disturbing state: Some were shoeless and nearly naked in the snow. Their well-stocked tent, hundreds of yards away, had been cut open from the inside, as if they had escaped in a hurry.

It took months for the rescue team to find the bodies of the remaining four hikers in a streambed. Their corpses had developed a strange orange hue and several had suffered gruesome injuries. One person was found without eyeballs. Another was missing her eyes and tongue.

Foul play was considered at first, but the clues didn't come together. An investigation produced no suspects or motives, and though some bodies were badly injured, there were no signs of a violent struggle. The Soviet Union initially concluded that a "compelling natural force" had caused the nine campers’ deaths, but that hardly settled the case.

Amateur detectives put forth alternate explanations. Some victims' clothing was slightly radioactive—a clue, they said, of the Soviet government covering up a nuclear weapon test gone wrong. One theory pointed to an argument over romantic tensions in the group that resulted in a deadly fight. Some even suggested that the hikers were targeted by aliens or a Yeti.

The Dyatlov Pass incident has evaded explanation since it occurred more than 60 years ago. But in early 2021, a study suggested the most compelling theory yet: The Dyatlov team had been driven from their camp and fatally injured by a rare type of avalanche. Experts have long suspected that an avalanche was involved, though critics have argued there were too many inconsistencies in the evidence.

The new report, however, is different. Using computer models inspired by the Disney movie Frozen, scientists have come up with a theory that may finally solve the mystery.

A Desperate Escape

February 1, 1959, was the last night the hikers spent at the camp, according to diaries recovered from the site. Dyatlov, a radio engineering student at the Ural Polytechnical Institute, had invited colleagues from his university to join him on the trip to Mount Ortorten in the remote northern Urals. Lyudmila Dubinina, Zinaida Kolmogorova, Yuri Doroshenko, Aleksander Kolevatov, Yuri Krivonischenko, Rustem Slobodin, Nikolay Thibeaux-Brignolle, Semyon Zolotaryov, Yuri Yudin, and Dyatlov made up the party. They set off in late January after traveling to their trailhead by train, bus, and sleigh. (Yudin left the trek early after falling ill and became the party’s sole survivor.)

After trekking through deep snow and thick pine forests for several days, a storm forced them off their route, and they set up camp on the slope of a mountain called Kholat Syakhl. Whatever happened next caused them to cut through their tent and escape, without proper footwear or clothing, in a howling blizzard.

Investigators knew the hikers understood the danger of being stranded in the wilderness in winter without food or shelter. So why had they died (from hypothermia, in six of the cases) so close to camp? And why had many of them left the tent without taking supplies or even putting on shoes?

An avalanche would answer these questions. If the Dyatlov group had been woken up by snow sliding toward them, they likely would have fled the area as quickly as possible. The scenario is easy to imagine, which is why the theory has endured for so long. But there are many reasons why people have resisted it, the biggest of which is that the searchers saw no signs of an avalanche when they found the Dyatlov camp.

The abandoned tent was torn open and covered in snow, but not buried as it would have been in the case of a typical snowslide. The shelter had been erected on the mountainside at an incline slightly less than 30°—the number usually cited as the minimum needed to start an avalanche. According to evidence from the scene, the crew tried to escape the camp roughly nine hours after pitching the tent. That means there would have been a long delay between the campers possibly destabilizing the snow and any avalanche that did occur.

In addition to these logistical problems, the initial avalanche theory didn’t provide satisfying answers to the case’s more baffling mysteries. Three of the group members died of traumatic injuries: Thibeaux-Brignolle from a fractured skull, and Zolotaryov and Dubinina from severe chest trauma. A doctor who examined the bodies compared their wounds to what he’d seen in car crash victims. The causes of death didn’t align with typical avalanche accidents, which usually kill people by suffocation. And even if an avalanche had driven the party away after battering some of them, that wouldn’t explain the radioactive clothing, the sickly orange skin, or the missing eyes and tongue.

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Then, last year, a revised version of the avalanche theory was endorsed by Russia. Following a new inquest, the government concluded that a rare, small slab avalanche had been the catalyst of the Dyatlov Pass tragedy. Slab avalanches occur when a layer of snow close to the surface comes loose from the layer beneath it and rolls down an incline in large chunks. This would have left behind less evidence than a more dramatic event, and the fast-moving snow blocks would have been capable of injuring some campers without smothering them.

Russia’s new report was certainly more convincing than a "compelling natural force," but there wasn’t much research backing it up. To convince skeptics of the slab avalanche theory, scientists needed to figure out a way to recreate what happened on the night of Feburary 1, 1959.

Recipe for Disaster

Johan Gaume's impression of the 2013 Disney film Frozen differed from most viewers. Where many people saw a light-hearted musical for kids, he saw the potential for a scientific discovery. This makes sense considering what Gaume does for a living: The Swiss scientist studies avalanches and the way they act under different conditions. After watching the animated characters escape from snow falling down a CGI mountain, he started planning a trip to Hollywood.

Gaume met with Frozen’s snow effects specialist and got permission to use the actual code used to animate snow in the movie. He worked with Alexander Puzrin, a fellow avalanche researcher from the Swiss Federal Institute of Technology, to apply an adapted version of the code to the Dyatlov Pass incident. Their findings were reported in a study published in the journal Communications Earth & Environment in January 2021.

With information from crash tests General Motors conducted on cadavers in the 1970s, the researchers demonstrated how a slab avalanche could cause traumatic injuries. Their computer simulation showed that a block of ice smaller than an SUV would have been capable of breaking the bones of the Dyatlov campers while they slept on their backs. The fractures wouldn’t necessarily have caused instant death, which would explain how the injured made it so far from the camp—likely with help from their luckier tent-mates—before succumbing to the damage.

The study also calculates how a type of wind known as katabatic wind may have triggered the slab avalanche hours after the group set up camp. There was no snowfall recorded in the area the night the party left their tent, so something else must have added pressure to the mountainside for an avalanche to occur. Katabatic winds are fast-moving, downward gusts propelled by gravity. Such winds could potentially transport enough snow to cause what looks like a spontaneous avalanche. This would have been possible even with the site’s relatively shallow incline. Though 30° is considered the threshold for avalanches, snowslides have been known to occur at lesser angles. Some data supports avalanches happening at close to 15° under the right conditions.

The base layer of snow discovered beneath the camp consisted of something called depth hoar, or sugar snow. These large, grainy snow crystals don't adhere easily to each other. In other words, the conditions at the Dyatlov campsite may have been the perfect recipe for a lethal avalanche.

The Mystery Endures

Gaume’s and Puzrin’s simulations may solve the problems of the angle, the delay, and the traumatic injuries often cited by critics of the avalanche theory. But other mysteries of the Dyatlov Pass incident are harder to run through a computer model. Many questions still surround the tragedy: Why were the bodies discolored? Why were some missing eyes and a tongue? Where did the radiation on their clothes come from?

Many of the more unusual elements of the case can likely be explained by the victim’s exposure to the elements. The hikers described as having orangish skin were found months after their disappearance, and they may have started to mummify. The length of time they were outside would also explain why soft tissue was missing from some of their faces. The eyes and tongues of dead bodies are easy pickings for scavengers.

The radiation may be the most controversial detail and the hardest one to decipher. One theory states that the thorium in the gas lanterns they brought with them was powerful enough to make their clothes slightly radioactive. It’s also possible that the trace amounts resulted from the bodies laying in direct sunlight for months.

We may have a possible explanation for how the Dyatlov party perished, but how they spent their last moments alive is still unclear. What happened in those hours or days between the avalanche and their tragic deaths is a question that will likely never be fully answered—and this new study doesn’t attempt to. As the authors write, "we believe that this will always remain an intrinsic part of the Dyatlov Pass mystery.”