John Bradford, president of SpaceWorks Enterprises, wants to talk about Mars, hibernation, and bears, which is tricky because — despite what grade school teachers sometimes claim — bears don’t hibernate. What bears do, perhaps better than any other species on Earth, is chill. Every winter, grizzlies crawl into their dens, bed down, and enter a state called torpor. Their internal temperatures drop by 10 degrees, their breathing slows with their heart rate, and their metabolic activity drops as they begin to cycle nitrogen that would otherwise be excreted in urine to prevent muscle atrophy. This feat of physiology is remarkable on its own, but the real reason spaceflight entrepreneurs are so interested in torpor is what would happen if you poked a resting bear: It would wake up and eat you.

Torpor isn’t deep sleep. It is sometimes considered a type of hibernation, and the two are similar. In both cases metabolic activity slows, although true hibernation is more extreme — some animals can reach near-freezing internal temperatures and thaw out just fine. It’s the closest thing the natural world has to suspended animation, a way to avoid the negative physical and mental effects of time in space by leveraging a mammalian superpower — one humans might, on some level, possess.

“We still really don’t understand a lot of the triggers and mechanisms for even why some animals do it,” says Bradford, who has enlisted the help of biologists working on these very questions. His thinking? If we can get a handle on how our mammal cousins shut down without suffering long-term ill effects, we might be able to replicate those results in ourselves.

“I’m very encouraged,” he adds.

Here’s what he imagines: Astronauts entering pods, slowly losing consciousness, and letting their internal temperatures drop as engines fire up and blast away. Six months later, these unconscious explorers wake up on Mars without recollection of the journey.

NASA buys into this vision, which sounds science fictional, but might become a key component of the plan to get humans to the Red Planet this century. Spaceworks is now in the second phase of a NASA-funded project to research the feasibility of inducing torpor in Mars-bound astronauts in order to keep them healthy and save money.

Human hibernation stasis suspended animation
A SpaceWorks design concept for a Mars-bound spacecraft.

As it turns out, the strongest argument in favor spaceflight hibernation is economic. Bradford estimates that a torpor habitat and launch system would weigh half as much as a traditional living space loaded up with food and oxygen tanks. Shipping costs to Mars work out to about $50,000 a pound, so when you’re talking savings in the realm of hundreds of tons, even a very large investment in research and design could pay off.

Plus, torpor might offer protections against bone density loss, muscle atrophy, and possibly even space radiation for astronauts on the long haul. “They’re still looking for good solutions to address those, and consequently you end up with multiple technology paths trying to solve each one of these individually, and we think we can with this one technology offer some benefits to all of those,” says Bradford.

From a medical perspective, it’s unclear at this point whether stasis would in itself protect against cellular damage from radiation, but from an engineering perspective, it’s a lot easier to implement shielding if astronauts are contained to a capsule.

Which all brings the question back around to feasibility. Humans do not typically hibernate, but many mammals do, and there are reasons to believe that we have our biology can be hacked to create a similar response. The best evidence is in rare and extraordinary cases where people have been found apparently frozen to death, only to come back to life once they warm up. As biochemist Mark Roth memorably put it in a 2010 TED Talk: “You’re not dead until you’re warm and dead.”

In 1999, Anna Bågenholm spent 80 minutes trapped under a frozen waterfall in Norway, and her internal temperature dropped to 57 degrees. Her heart was stopped for three hours, and yet thanks to a careful medical resuscitation, she came back to life and recovered almost completely.

In 2006, Mitsutaka Uchikoshi of Japan got lost in the forest and was found 24 days later in a hibernation-like state. His body temperature was just 72 degrees, and he had no recollection past the second day of his absence. He also recovered.

These days, Roth is working to develop a chemical way to induce hibernation or suspended animation in humans as an aid for emergency medical treatment. If you put someone in stasis right after a heart attack, stroke, or traumatic injury, his thinking goes, you can essentially stop the clock, giving doctors time to fix the problem while preventing the damage to the brain and other organs that would otherwise result from oxygen deprivation.

Hydrogen sulfide seems to have some promise as an inducer of suspended animation. The compound binds to oxygen receptors, which decreases the body’s demand for O2 and causes metabolism to shut down. The clinical trials were canceled, but Roth hasn’t given up on similar compounds that could help minimize injury from blood rushing back into tissues after a medical procedure.

SpaceWorks Enterprises torpor Mars habitat.
Crew members would be fed nutrients intravenously through the flight.

Still, most of the medical research into human stasis is focused on finding ways to safely slow human metabolism for a period of a few hours to a few weeks. To get to Mars, that timeline will have to be expanded significantly, although that work will certainly provide crucial insights that will guide the future of space hibernation. And in order to accomplish that there will need to be human trails, which, again, gets tricky.

“Other than space flight, there isn’t really a compelling reason to do this to a healthy person,” says Bradford.

Even though Leroy Chiao, former NASA astronaut and commander of the International Space Station, is cheerleading for the project, not all astronauts are pumped to go under either. “At one of our technical conferences Buzz Aldrin voiced concerns,” says Bradford. “He didn’t want to do it. He wants to be awake.”

Bradford understood where the NASA vet was coming from, but he has a slightly more pragmatic perspective.

“If it means the difference between being able to go to Mars, and not,” says Bradford, “I think everybody will do it.”

Photos via SpaceWorks Enterprises, Inc., SpaceWorks Enterprises, Inc. (SEI)