Amazing stories of animals and humans surviving extreme cold are fueling futuristic research that verges on sci-fi. We took a deep dive into the DNA of icy wood frogs, a novel approach to cardiac arrest, the potential for cryopreservation, and other shocking developments from the new science of freezing.

Miracle on Ice

The sun was setting over the Tantalus Mountains on March 31, 2014, when Christine Newman snowshoed past an empty ranger station and climbed the final rise to the Elfin Lakes shelter in Garibaldi Provincial Park, about 45 miles north of Vancouver. Twenty-four years old, with long blond hair, she was wearing rented snowshoes and a small daypack and was hiking alone. Temperatures were headed for the twenties as she settled into a bunk with more than a dozen other campers there for the night.

At breakfast the next morning, someone remarked that at around 2 a.m., Newman had told her that she was leaving because she wanted to get an early start back to the trailhead, about seven miles away. The night had been clear, and the trail was well marked, so no one worried. They finished their meals and headed out for the day.

At 9 a.m., six friends from the shelter departed on skis and snowshoes for the 22-mile trek across the Garibaldi Névé traverse. It was bright and sunny, and the wide-open plain was carpeted with a few inches of fresh snow. About a quarter-mile from the cabin, the lead skier noticed a backpack lying near a small hemlock tree. Immediately, he recognized it as Newman’s. Others in the group saw tracks and heard a strange moan. Following the sound, they spotted the top of Newman’s head sticking out of a tree well. She was gasping for air, and as Barb Linton, a snowshoer from nearby Squamish, remembers, “Her eyes were wide open, she wasn’t blinking, and her hair was straggled down. We tried to pull on her, but she was stuck. We couldn’t move her. She was frozen into the snow.”

By the time they got her out, Newman had likely been buried up to her chest for seven hours. She was unconscious and in extreme hypothermia, and she had no detectable pulse. Linton, a former search-and-rescue volunteer, and her companions covered Newman with a sleeping bag and started CPR, while another friend on snowshoes rushed back to the hut and yelled for someone to call 911. It took two hours for rescuers to arrive and another two and a half hours to transport Newman to the hospital. Her body temperature was 62 degrees, and her chances of survival were slim. Clinically, she was almost dead.

Six years ago, Doug Brown, an emergency medical physician, mountain climber, and ultrarunner in Vancouver, would have said of Newman, “This patient is doomed. Let’s stop resuscitation—we’re torturing this body.” But doctors are discovering that when it comes to hypothermia, the line between life and death isn’t clear-cut. If you become severely hypothermic before your heart stops, the cold can actually become a protectant, making it possible for you to enter a state similar to suspended animation in which your metabolism slows to such a pace that your brain and organs can survive on a whisper of oxygen. (For every one-degree-Celsius drop in temperature, metabolism slows by 5 to 7 percent.) If a victim is discovered in time, he’ll appear dead—dilated pupils, no detectable pulse, no breath—but if a rescuer knows to start CPR and get help, he might have a fighting chance. This is true especially if he’s transported to a hospital with the technology to perform a procedure called extracorporeal membrane oxygenation, an advanced life-support system. ECMO involves a heart and lung machine that siphons the blood out of the body, filters, warms, and oxygenates it, and then zips it back in. Then doctors jump-start the heart with electrical current. The technology was invented decades ago, as life support for infant preemies, and is also used during open-heart surgery. Only recently has it gained wider use to save the lives of hypothermia patients.

Brown learned from European colleagues at a 2009 medical conference in Switzerland, where ECMO’s use for hypothermia treatment was highlighted, that patients like Newman still had a good chance of surviving, and he began spreading the word among colleagues and search-and-rescue personnel in British Columbia. The team bringing Newman in called Brown, and he arranged to have her taken to Vancouver General, a hospital capable of administering ECMO.

Brown consulted with Vinay Dhingra, the on-duty critical-care specialist when she arrived. Dhingra had seen deep hypothermia before. “But not like this,” he says. “We knew we had to be aggressive with her treatment—it would be futile if we weren’t.” They warmed her blood and then shocked her heart. “Right away we got a pulse,” Dhingra says. A few hours later, with further treatment, she began to wake up. “She started to focus on us,” Dhingra says, “following simple commands like shaking her head to answer questions.” The next day, she was weaned off ECMO. On day three, she was removed from life support altogether. That evening, around 2 a.m., the night-shift nurses heard sounds coming from the ICU—Newman was singing. Two weeks later, she was released from the hospital.

How Cold Is Too Cold?

Medical journals have published accounts of frozen people who were brought back from the edge of death and went on to live normal lives, with no brain damage, even after as many as seven hours of cardiac arrest. (Under normal circumstances, doctors call it quits at 20 minutes.) Hence a popular saying in medicine: “You’re not dead until you’re warm and dead.”

“We’ve learned that there really is no temperature so low that you shouldn’t try to save someone,” says University of Manitoba thermophysiologist Gordon Giesbrecht, a.k.a. Professor Popsicle, who is one of the world’s leading experts on hypothermia. “We used to say maybe 20 or 15 degrees C”—68 or 59 degrees Fahrenheit—“and below that don’t bother. But then along came some cases that even at 13.7 degrees C”—about 57 degrees Fahrenheit—“given proper care, people survived. So now we’ve taken away the low-temperature threshold.”

The survival stories make headlines: “Brought Back from the Dead!” Thirteen-month-old toddler Erika Nordby was declared a miracle baby in February 2001 after she’d wandered out through an unlocked door on a two-degree night in Edmonton, Alberta, wearing nothing but a diaper and a T-shirt. Stunned to find Erika missing at 3 a.m., her mother looked outside and saw the baby on the ground. At the hospital, doctors managed to rewarm Erika; 24 hours later, she woke up and cried for her mother.

“We’ve learned that there really is no temperature so low that you shouldn’t try to save someone,” says thermophysiologist Gordon Giesbrecht, an expert on hypothermia.

In May 1986, a group of high school students and teachers had climbed nearly to the top of Oregon’s 11,249-foot Mount Hood when a spring snowstorm blew in and forced them to retreat. At 9,000 feet, facing temperatures of 15 degrees and winds as strong as 60 miles per hour, they built a snow cave, hoping to wait out the weather. In the morning, two of the students managed to make it back to camp, and a rescue mission was launched, but it was delayed another day by the storm. Eventually, after repeated attempts, the remaining students and teachers were brought down off the mountain and taken to various Portland-area hospitals to receive ECMO. Most were too far gone to respond to treatment, but two 15-year-olds survived. (ECMO was used as early as 1977 in the U.S. for hypothermia, but the procedure still isn’t widespread or often taught in medical school.)

More recently, in April 2014, a 15-year-old boy named Yahya Abdi stowed away in the wheel well of a Boeing 767 that flew from San Jose, California, to Maui. Aviation and medical experts were in disbelief: how could he survive the air pressure at 38,000 feet and temperatures as low as minus 80 degrees? According to reports, Abdi remembered blacking out shortly after takeoff, but his heart apparently kept beating very slowly. When the plane landed in Hawaii, five and a half hours later, he emerged from his hiding spot unharmed.

Understanding how some people cheat death and pinpointing the precise moment when hypothermia sets in are mysterious affairs. In general, the dominoes start to fall when a person loses body heat faster than it’s produced. The first signs of mild hypothermia begin at the 95-degree mark with the onset of uncontrollable shivering—the body’s attempt to warm itself. Gradually, as you creep toward moderate hypothermia (90 degrees), skin grows pale, lips turn blue, and speech begins to slur. Sink deeper than 82—severe hypothermia—and you lose consciousness. Left in the cold, your body will continue to drop in temperature, and your heart will beat slower and slower until you experience cardiac arrest and die.

However, if you’re discovered during the stage in which your heartbeat is slowing, like Christine Newman was, your odds of survival improve. Sometimes the jostling caused by pulling a victim out of the ice can trigger cardiac arrest, referred to as rescue collapse. But because a person is in a cold state, and the brain requires less oxygen, CPR can keep a victim alive for hours, compared with minutes in warmer conditions.

If you’re transported to a hospital with an ECMO-trained staff, you have a 50 percent chance of surviving without neurological damage, according to Beat Walpoth, a cardiac surgeon at Geneva University Hospitals in Switzerland, who published some of the earliest studies on the effectiveness of treating severe hypothermia. Walpoth is currently leading the International Hypothermia Database, which is gathering patient case histories from around the world to create guidelines for treating hypothermia victims.

Meanwhile, what doctors are learning from survivors like Newman is providing clues to medical technology that could rescue others assumed dead in the cold—and also potentially save heart-attack, car-accident, and gunshot-wound victims. And research at the frontiers of extreme cold doesn’t stop there. Elite athletes, for starters, are jumping into cryotherapeutic chambers, human-size vessels filled with liquid-nitrogen-chilled air, hoping to accelerate recovery and improve performance. We are on the cusp of a new era in far-out science, and it’s rooted in ice.

The Case of the Amphibian Popsicle

In the past half-century, we’ve become very good at freezing tiny things: blood, stem cells, tumors, semen, eggs, ovarian tissues, seeds, embryos. But researchers looking for ways to put the chill on complex tissues and organs face the same challenge that plagues the steak in your freezer: ice crystals, or freezer burn. When that forms, it damages tissues.

So far no one has figured out how to overcome this problem. But some scientists think a tiny amphibian, the wood frog, might hold at least part of the answer. With an expansive range stretching from Georgia to north of the Arctic Circle, the wood frog spends weeks, even months, in a state of suspended animation. It can freeze solid in winter, devoid of all vital signs, then quickly thaw in the spring, hopping off to mate.

Some of the latest research in hibernating amphibians comes from Fairbanks, Alaska, where a 29-year-old scientist named Don Larson recently kept tabs on wild wood frogs as they overwintered. Scientists have long known about the species’ cold-weather coping strategies, but Larson’s study revealed that the frogs can remain frozen for as long as seven months, and at colder temperatures than previously known—down to almost zero degrees. “They’re spending more time frozen than most foods can be left in your freezer,” Larson says.

His study adds to 25 years of research at the University of Miami’s Laboratory for Ecophysiological Cryobiology in Oxford, Ohio. “These animals have been able to pull off something really remarkable,” says senior research scholar and zoology professor Jon Costanzo.

Costanzo’s studies have shown that just before freezing, the frogs flood themselves with huge quantities of glucose, which behaves like a kind of cryoprotectant. As the mercury drops the frog’s body freezes, with just enough water left in the interior of its cells to prevent its membranes from being damaged until the days begin to grow longer and the ground becomes warmer. Then, over the course of a day or so, the animal regains a pulse and springs back to life.

Frogs aren’t very similar to humans, but this knowledge has applications in the important field of organ transplants. Taking a cue from the frogcicles’ ability to flash-freeze and spontaneously defrost, doctors hope to one day use cryopreservation to extend the use-by date of donor organs (currently four to six hours for a heart or lungs, 12 to 18 hours for a liver). Every ten minutes, a patient in the U.S. is added to the organ-transplant waiting list. Each day, an average of 79 people receive transplants, but 22 perish waiting for a phone call. The solution would be to preserve organs indefinitely, so they can be held until a suitable match is found.

One of the biggest breakthroughs in the attempt to freeze organs came in 2009, when cryobiologist Greg Fahy and his California-based company 21st Century Medicine, unveiled a technique that came close to conquering the ice-crystal conundrum. He used a chemical cryoprotectant to successfully cool a rabbit kidney to a vitrified, or glass-like, state, then thawed and transplanted the organ into a live rabbit. His landmark success offered hope that vitrification would revolutionize organ banking. Trouble is, ten years later, no one has figured out how to apply the technique to human organs, because using higher concentrations of chemical cryoprotectants can poison the cells and tissues they’re supposed to protect.

Other scientists are working with the cold technology already at hand. In the 1950s and ’60s, research by scientist Peter Safar, known as the father of modern resuscitation, led to the experimental use of therapeutic hypothermia for treating comatose patients in the ER. He and his colleagues showed that the therapy, which involves a number of techniques to chill the body (including cooling blankets, ice, and catheters filled with a cold saline solution), successfully reduced tissue injury and brain damage from lack of blood flow, particularly in people who’d suffered a heart attack or stroke. The technique is still used today to treat those conditions, along with spinal injuries and newborn babies showing signs of impaired brain function.

At the UPMC Presbyterian hospital in Pittsburgh, surgeons are experimenting with putting critical patients who have suffered severe gunshot and knife wounds into a state of suspended animation by flushing their arteries with ice-cold saline to supercool the brain and organs.

“Time is of the essence,” says Sam Tisherman, an expert in trauma surgery who is spearheading the human trials and is preparing to launch a second study in Baltimore. “We are racing against the clock to control bleeding before irreversible damage occurs to the brain and other organs.” The procedure, called emergency preservation and resuscitation, buys surgeons more time to control a patient’s bleeding. After the repair work is done, the doctors gradually rewarm the patient by restoring natural blood flow.

“The goal is to save people who would otherwise have died,” says Tisherman, who has played close attention to stories of frozen survivors. “Knowing that people who cool very fast can tolerate not having oxygen or blood flow for an hour or more inspired our work.”

Chilling Out

Though athletes have been icing post-workout for decades, debate continues as to whether it actually boosts recovery. But that hasn’t stopped the recent boom in ice technology. Cryotherapy salons are popping up in cities around the country, offering a quick alternative that’s like an ice bath on steroids.

Spa-goers strip down to their underwear and put on athletic socks, terry cloth robes, and wool mittens for a trip inside a tin-can-shaped cryotherapy chamber filled with air that has been nitrogen-cooled to between minus 184 and minus 264 degrees. The goal is to bring a person’s skin temperature down to 40 degrees as quickly as possible and maintain that temperature for a minute or two. Adherents claim that this triggers the body to go into survival mode, sending blood from the extremities to the core, where it is enriched with oxygen and other nutrients. Afterward, as the body rewarms, the enhanced blood is pushed back to the extremities. The treatments are based on research pioneered by Japanese doctor Toshima Yamauchi, who invented the procedure in the 1970s to help patients with rheumatoid arthritis, noting that the majority of those who went through the process were completely relieved from their symptoms and pain.

At KryoLife, the first cryotherapy studio in New York City, which opened in April 2014, owner Joanna Fryben boasts the treatment’s effectiveness for preventing joint swelling and reducing pain, boosting metabolism and weight loss, erasing wrinkles, and easing depression. With such promised results, who wouldn’t want to freeze his ass off? Double-gold-winning distance runner Mo Farah has long been a fan, and Steve Weatherford, known as the fittest man in the NFL, espouses the benefits of his weekly trips to KryoGenesis in Paramus, New Jersey.

I tried a session at KryoLife last August. In a robe, gloves, and socks, I waited for my turn to enter the cryotherapy chamber. Once inside, my head sticking out from the top, a technician told me to toss the robe to him. Immediately, I felt the extreme chill of a fog-like vapor swirling around my body. For the next three minutes, the technician, who closely monitored how I was feeling, talked me through the experience, a welcome distraction from a stinging pain at the back of my knees and elbows. “Those are the areas where the skin is thinnest,” he said. I danced around, waiting for my time to be up.

After exiting, clients are encouraged to warm up on a rowing machine or stationary bike for a few minutes. I didn’t feel the surge of endorphins others mention. Instead I felt tired. But some patrons I met were emphatic that the treatment works. “What a rush,” said nutritionist Oz Garcia when he exited the tube, teeth chattering. He credits the treatments for weight loss (the body purportedly burns calories fighting the cold) and pain relief from a back injury, and said he’s done cryotherapy at least 200 times. “It’s not for everyone,” he says, “but it has accrual results. It gives you a leaner, tighter body and better moods, and you’re less inflamed.”

Despite the buzz, the safety and effectiveness of cryotherapy chambers aren’t well understood. The treatment lacks FDA approval, but there haven’t been many reported incidents of safety issues other than a few cases of mild frostbite. The treatment did make headlines recently after an employee at a cryotherapy salon near Las Vegas died. As she was closing up on the night of October 19, 2015, Chelsea Ake-Salvacion reportedly texted her boyfriend that she planned to hop into a chamber for a quick session. The next morning, a coworker discovered her body frozen inside. Ake-Salvacion’s death was ruled an accident.

As for cryotherapy’s benefits for athletes, one study published by the National Institute of Sport, Expertise, and Performance in Paris evaluated inflammation levels in a group of runners who spent 48 minutes on a treadmill. In one trial, the runners did cryotherapy afterward, once a day for five days. The runners also tried daily 30-minute sessions of quiet sitting. The researchers reported that following cryotherapy, the runners had fewer blood markers of inflammation, suggesting that athletes could gain an edge through quicker recovery times.

Other researchers remain skeptical. A recent report from the University of Portsmouth in England, lead by university sport and exercise scientist Joseph Costello, reviewed studies that compared the effects of whole-body cryotherapy on muscle soreness with a placebo or no treatment at all in 64 active adults. The report found no evidence to suggest that the super-chilled air had a positive effect on recovery. Costello concluded that much more research is needed to understand whether the therapy works.

Even more extreme is the controversial process of human cryopreservation, which has been around since the 1960s. Adherents count on a future in which molecular nanotechnology and other advances will be able to reverse the damage done to tissues during the freezing process, bringing frozen people back to life and then curing them of whatever killed them in the first place. The process looks something like this: The cryo company arranges to have staff on site when a client’s heart stops. Within minutes they plunge the person into an ice bath and put him on life support to minimize brain-cell death. They administer drugs to help keep the blood flowing, then circulate cryoprotectant chemicals throughout the body via an IV. In the end, the person is transported to the cryo facility in a stretcher-like basket filled with ice and then stored in minus-320.8-degree liquid nitrogen inside a vessel similar to a giant thermos bottle.

In Scottsdale, Arizona, the Alcor Life Extension Foundation currently has 141 people (and some of their pets) preserved. Among them are Hall of Fame baseball player Ted Williams, his son John Henry Williams, and Emmy Award–winning sitcom writer and producer Dick Jones.

Whole-body cryonics costs upwards of $200,000, or you can go the cheaper route: $80,000 to have your head lopped off and preserved, as Alcor cofounder Fred Chamberlain Jr. did in 2012. How will Chamberlain come back from the dead without a body? The company’s answer: he’ll grow a new one. So-called neuropreservation is founded on the idea that a replacement body can be grown around the brain using future tissue-regeneration technology. After all, who wants to be immortal in an 80-year-old body?

Lessons from the Formerly Frozen

In the meantime, survivors of extreme freezing may offer clues to the cryopreserved of the future. Anna Bagenholm holds the world record for living through the lowest core body temperature: 57 degrees. On May 20, 1999, the then 28-year-old was skiing with two friends down a waterfall gully in northern Norway when she fell into the water and became wedged between rocks under a thick layer of ice, with a pocket of air to breathe. Her friends tried to pry her to safety, but they quickly discovered that they couldn’t free her and phoned for help, watching in anguish as she struggled. Forty minutes later, Bagenholm stopped moving.

About an hour passed before a rescue team arrived. They cut a hole in the ice and pulled Bagenholm’s limp body out of the water. She wasn’t breathing and had no detectable pulse. The paramedics started CPR, and a few minutes later a helicopter arrived to medevac her to Norway’s Tromso University hospital.

At the hospital, a team of cardiac surgeons, anesthesiologists, and nurses were waiting. They continued doing CPR and prepped Bagenholm for ECMO. As her core body temperature crept back up, her heart began beating again. Bagenholm spent six weeks in intensive care and eventually moved to a rehabilitation unit. Her mental function was completely normal upon waking, but her physical recovery took much longer. After two years she returned to work and resumed some hiking and skiing. Today she’s a radiologist in the hospital where she was saved, and she lectures at conferences about the potential to rescue others like her. She gets annoyed when she reads in the newspaper that a person was found in the cold and declared dead before they were taken to the hospital and rewarmed. “The most important thing is to not declare people dead outside. If it’s possible, start CPR, take them into the hospital, put them on ECMO, and rewarm them with everything you’ve got. Don’t give up. Even if it looks like the person is not going to make it, you have to keep on until it’s really over.”

Doug Brown, who emphasizes that doctors should use ECMO only when they believe a patient has a good chance for survival—that is, those like Christine Newman and Bagenholm who became severely cold before cardiac arrest—has created a group in British Columbia to establish clinical-practice guidelines for hypothermia. “Change in health care is very frustrating,” he says. “Most places in the U.S. don’t have protocols in place for getting hypothermic cardiac-arrest patients to ECMO.”

Newman hasn’t given any interviews about her accident, but she did release a YouTube video last March, near the one-year anniversary, in which she thanked her rescuers. Aside from some cold sensitivity in her hands and a few scars, including two on her thighs from the ECMO procedure and one on her back from being pulled out of the ice, she said she’s feeling good and doing most of the things she has always enjoyed.

For Bagenholm, it took some time to fully grasp what had happened to her. She remembers waking up in the hospital after her accident. “I was paralyzed from the neck down, so I couldn’t move,” she says. Although she could remember other things about her life, the accident was a blank. “You know when you have a computer and you write on it, and then suddenly the power is out, everything on the hard drive is still there, but the things on the screen are gone. That’s how it was for me,” she says. “Everything I’d saved was still there, but the things that happened that day were gone. I still don’t remember.”

Bagenholm’s case is often trumpeted as a miracle, but she doesn’t believe her rescue was foreordained. “It’s not a miracle,” she says. “It’s physiology. The miracle is that we’ve learned that it’s possible to save people like me.”

Rene Ebersole is a writer and editor at Audubon. Her work has also appeared in Nautilus and Mental Floss, among others.