Dive into a science fiction story that sends humans exploring the reaches of space, and you'll likely find the crew waking from some kind of suspended animation. But the idea is also bandied about in science fact: human hibernation would be a boon to astronauts traveling for months or years. So far, research in this area remains fairly speculative, though, in experiments, surgeons have cooled people down to extend surgeries.
The problem is, hibernation isn’t just a deep, months-long sleep. And even if it was, humans aren't built to survive such inactivity.
What we do know about hibernation comes from studying bears, squirrels, lemurs and dormice. All hibernators wake up occasionally—to stretch and perhaps urinate or defecate. Some snack on stored food; others fast and live off of internal fat reserves. The information scientists are gleaning from these habits is now helping to inform study of potential human hibernation, reports Eric Niiler for the Washington Post.
“We see the science has advanced enough to put some of the science fiction into the realm of science reality,” Leopold Summerer, head of advanced concepts team of the European Space Agency, told Niiler. “It doesn’t mean we will have hibernating astronauts anytime soon, but we are learning from nature how to understand some of the things that happen to animals during hibernation, such as preventing bone loss or preventing muscle loss. This is already something that would be a great benefit for long-distance spaceflight.”
The ESA, NASA and other space agencies are interested not only because humans in space would skip months of boredom if they could hibernate, but because they would need less food, produce less waste and require less space. But they would need a hibernaculum, or suitable space in which to hibernate, reports Tariq Malik for Space.com. He writes:
As envisioned by ESA researchers, such a shelter would provide the proper environment for hibernation - such as the proper temperature - and also serve as a bed in the waking part of the mission. It would also have to protect crewmembers from solar flares, monitor life functions and serve the physiological needs of the hibernator, [Mark Ayre, with ESA] said.
Some clues as to what humans will need to survive long-term in space will likely come from astronaut Scott Kelly’s year in space. (However, privacy concerns may keep the data from that twin study from becoming public.) So for now, our best clues are coming from animals.
Kelly Drew, of the University of Alaska at Fairbanks, is one researcher looking at hibernation in animals, Niiler reports.
Kelly and her colleagues at the university’s Institute of Arctic Biology are looking at how the Arctic ground squirrel can get so cold without dying. She believes she has found the molecule that does the job, the A1 adenosine receptor. While she has learned that stimulating this receptor makes the animal get cold, she hasn’t found what triggers it.
“We don’t know what the natural signal is for torpor,” she said. “We don’t know where the signal occurs in the brain — it could be in the brain stem or the hypothalamus.”
Still, humans will face challenges that hibernating animals don’t have. Hibernating bears are able to recycle the urea waste generated by metabolizing their fat reserves. Instead of excreting urea, they can actually break it down and use it to build up muscle and organ tissues while they sleep, reports Forrest Wickman for Slate. Humans can’t do that. This fact gives some researchers doubts that human hibernation will ever be a thing.
“I think it’s probably not doable,” H. Craig Heller, of Stanford University told Niiler. “The hibernator [animal] has evolved so that all the enzymes and biochemical systems are adapted to run at low temperature. That is not true of animals that don’t experience it. We can lower body temperature and survive that for a short period of time; it’s unlikely we can allow all of our systems to go to a much lower temperature and continue to function.”
More research will offer a definitive answer, either way. However, we don’t need studies to predict that no hibernating human will be as cute as this snoring dormouse: