They Used Xenon to Climb Everest at Warp Speed

Their history-making attempt on Everest was a success. The BBC reports four British men summited Everest early Wednesday, having completed the climb in roughly four days and 18 hours. They avoided the typical weekslong acclimatization period by using xenon gas two weeks prior to the climb. The attempt hinged on xenon's ability to trigger the kidney's production of erythropoietin (EPO), which ups the count of red blood cells and hemoglobin and—the men believed—would serve as a substitute for the gradual acclimatization and buildup of red blood cells that typically occurs over weeks spent at Base Camp.

The team did spend three months prepping at home, including by sleeping in low-oxygen hypoxic tents for six weeks. The AP reports they flew from London to Kathmandu last Friday and began climbing as soon as they reached Base Camp via helicopter, and did rely on supplemental oxygen, as many climbers do. The BBC offers one asterisk: While their overall time on the mountain was a record, they're well off the record for the fastest Base Camp-to-summit time: Lhakpa Gelu Sherpa managed the feat in 10 hours and 56 minutes in 2003, though he'd acclimatized on the mountain for weeks beforehand.

The men's attempt wasn't without controversy, and the debate continues even in the wake of their completion of the climb. Damber Parajuli, president of the Expedition Operators Association of Nepal, offers one view: that "acclimatizing on the mountains is the basic rule of mountaineering. If that is not done, then authorities should not be giving them certificates certifying that they climbed the mountain." For their part, Nepal's tourism department officials say they weren't aware the climb was happening, noting, "Now that we know about it, we will be discussing the issue and decide on our future course of action."

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The AP reports that Nepal has no rules regarding how many days climbers must spend acclimatizing or making practice climbs. Lukas Furtenbach, whose company organized the expedition, pushed back on the criticism, telling Reuters, "Shorter expedition also means less garbage, less resources, less human waste in this sensitive environment." (More Mount Everest stories.)