Did British mountaineers George Mallory and Andrew Irvine reach the summit of Mount Everest in 1924 – 29 years before the first documented ascent of the highest mountain on Earth? It's a question that mountaineering enthusiasts worldwide have been asking for decades – so much so that many books have been written about the subject. 

New Zealand's Edmund Hillary and Tenzing Norgay of Nepal are in the record books for their 1953 feat. But now US mountaineer and filmmaker Jimmy Chin has found a very old mountaineering boot on the Central Rongbuk Glacier below the north face of Everest – with the remains of a foot and a sock on which a label with the inscription "A.C. Irvine" is sewn.

"I think it literally melted out (of the glacier) a week before we found it," Chin told "National Geographic" magazine. So is the 100-year-old mystery of Mallory and Irvine about to be solved? DW tries to answer the key questions.

What do we know for sure about the summit attempt 100 years ago?

In 1924, Mallory, 37, and Irvine, 22, were part of a British expedition that had set itself the goal of completing the first successful ascent of Mount Everest. They climbed on the Tibetan north side of the mountain because Nepal was off-limits to foreigners at the time.

Mallory and Irvine set off on their summit attempt on June 6 from the North Col at around 7,000 meters (22,966 feet), accompanied by a few Tibetan helpers. The next day they reached their last high camp at around 8,200 meters. There, the last Tibetans turned back – and took a note from Mallory to fellow expedition member Noel Odell.

"We'll probably start early to-morrow (8th) to have clear weather," it read.

In the note, Mallory also gave an indication of where and approximately when Odell was likely to see them the next day. When the cloud cover briefly broke on June 8, Odell thought he saw two moving dots on a rock step on the northeast ridge. After that, the trail of the two was lost.

Did other expedition members go looking for the two missing men?

When there was no sign of Mallory and Irvine, Odell climbed once more to the last high camp and from there a little further, but a violent storm forced him to turn back.

The harbingers of a monsoon made a further search impossible. Expedition leader Edward Norton then sent a telegraph to the London daily newspaper "The Times," which read: "Mallory and Irvine killed in last attempt."

Norton had reached an altitude of 8,570 meters during the expedition – unlike Mallory and Irvine without the use of bottled oxygen. This remained an Everest altitude record without a breathing mask until 1978, when Reinhold Messner and Peter Habeler reached the highest point on earth at 8,849 meters for the first time without bottled oxygen.

What clues to the fate of Mallory and Irvine were later discovered?

In 1933, members of another British Everest expedition found Irvine's ice axe at an altitude of 8,460 meters. Individual climbers from Chinese Everest expeditions in 1960 and 1975 and a Japanese expedition in 1995 reported that they had seen a very old corpse on their respective ascents. The altitude information varied between 8,100 and 8,500 meters. The information could not be verified.

On May 1, 1999, American mountaineer Conrad Anker, a member of an international search expedition, found Mallory's body frozen in the rubble at 8,159 meters. Mallory's leg was broken and severe head injuries were visible – clearly the result of a fall. Irvine remained missing. A small Kodak camera with which the two climbers wanted to document their ascent was not found.

Is there any doubt the boot belonged to Irvine?

Not really. The shoe was studded with steel nails, as was common practice among mountaineers in 1924. The crampons used today only became established much later. The brittle condition of the leather is also consistent with a 100-year-old shoe that has been lying in the ice for a long time.

The most important clue, however, is the label with the inscription "A.C. Irvine". The mountaineer's full name was Andrew Comyn Irvine. A DNA test could provide certainty. Irvine's descendants have agreed to provide DNA samples for comparison with the remains of the foot that have been found.

What conclusions can be drawn from the discovery of the shoe?

The first is that Irvine really did die on Mount Everest.

"It's an object that belonged to him and has a bit of him in it," said Irvine's great-niece Julie Summers, who has written a biography about him. "It tells the whole story about what probably happened." 

For years after his disappearance, Irvine's parents had left a light on and the door unlocked at their house in Birkenhead near Liverpool, in the hope that Andrew would one day come home.

German alpine historian and mountaineer Jochen Hemmleb was on site at Everest during the 1999 search expedition and was instrumental in the discovery of Mallory's body through his years of research. Hemmleb describes the recent discovery as "a seminal find." However, he also warns against jumping to conclusions.

"There are several possibilities how Irvine's body could have ended on the Central Rongbuk Glacier," he said.

"He could have fallen from somewhere on the Northeast Ridge. He could have been swept down by an avalanche from somewhere on the north face. Or his body could have been thrown off the mountain."

So did Mallory and Irvine actually reach the summit?

We just don't know.

"For now the find – despite its poignancy – doesn't shed much light at all about whether Mallory and Irvine made the summit or what happened to them," Hemmleb said. "I don't see a solution to the mystery so far."

This is especially sogiven the missing camera, which could possibly provide information, has still not been found.

However, American mountaineer Jake Norton, who, like Hemmleb, was part of the 1999 search expedition, is "sure there's far more to the story" – and it will be "shared in due time."

Jimmy Chin doesn't want to go into detail about where exactly he and his colleagues found Irvine's remains – so as not to encourage trophy hunters to rush to the bottom of the north face of Everest. He was confident that other artifacts and perhaps even the camera were nearby.

"It certainly reduces the search area," he said.

This article was originally published in German.