Space travel takes a really long time.

And if we ever want to visit  a planet other than Earth, we’re going to need a way  to keep people physically and mentally healthy for those long-haul trips. To get around this problem,  science fiction writers sometimes place their fictional spacefarers in some sort of stasis or suspended animation.

And while we don’t have that –  yet – some researchers see it as the most viable way to get  us from place to place in space. They’re taking inspiration from a natural process that occurs in other animals: hibernation. But to pull it off, they’ll  need to figure out how to get around the ways our own bodies  keep themselves running. [♪INTRO] Even travelling to other planets within our solar system would take months or years.

In the best-case scenario,  with our current technology, a trip to Mars would take about 7 months each way. Supporting astronauts on such lengthy missions will require lots of supplies. They’ll need to bring their own food, water, air and medical equipment.

That’s a lot of luggage to load onto your spaceship, but not a lot of space. So to conserve some of these limited resources, some researchers are looking for ways to mimic hibernation in humans. During periods where resources are scarce, some animals cope by slowing their metabolism.

That way, they don’t consume  as much of, well, anything. They don’t breathe as often,  their body temperatures drop, and they don’t need to eat  or drink or poop as much. This sluggish state is known as torpor.

When animals hibernate, it  involves periods of torpor lasting days or weeks, with a day  or two of activity in between. If we could get human bodies  to do something similar, our space journey wouldn’t need as much stuff. We don’t really know how hibernating  animals trigger this state.

But we do know that humans haven’t  evolved to do it naturally. If we want to imitate torpor  or hibernation in space, we’re going to have to do so by artificial means. The good news is that we can already copy some of the effects of torpor in the  short term by using medicines.

We use sedatives to slow  people down and anesthesia to keep them unconscious  and immobile during surgery. Cold temperatures can also slow a person’s metabolism, but there’s a catch. Our bodies have to maintain  a constant temperature.

If things dip too low, our bodies  will expend more energy to stay warm. And that’s when your body starts to shiver. Our muscles quickly contract and release, which builds up heat, though it does cost energy.

So there’s the conundrum: If we want to save energy by cooling down the  bodies of future astronauts, we have to prevent them from shivering. But, if we can limit shivering  and make our bodies tolerate cold temperatures, the cold and anesthetics  together might be able to slow a person’s metabolism enough to put  a real dent in the amount of stuff they need to bring with them on  their road trip through space. Some scientists are looking  into how astronauts might actually achieve this during  long-haul space flights.

Spacefarers might stay cool using ice packs, cooling wraps, or IV tubes  filled with cold saline solution. On the medicine side, they might use inhaled anesthetics like xenon gas or nitrous oxide. Or they might rely on the  same kinds of IV medicines that help put people to sleep before surgery.

We might even be able to  induce torpor using ultrasound. Besides cutting down on the  packing list, this combo of cooling and sedation offers some other advantages. Some studies suggest that it  could protect against DNA damage from the radiation that astronauts  will likely encounter in space.

And hibernating might help astronauts cope with the psychological challenges  of months in the void, if they can nap most of the  way to their destination. We haven’t tested anything like this at the time scales we’d need for space travel yet. But researchers are starting  to look at how these different approaches affect metabolism  over, say, a few hours.

One 2025 study looked into using a sedative that doesn’t actually require  people to be fully unconscious. Scientists wanted to see if  they could slow a person’s metabolism without needing full anesthesia. Instead, they used a sedative  called dexmedetomidine.

Doctors use this drug to start  the process of putting people to sleep before they start  surgery and full anesthesia. And it’s been shown to prevent shivering as people get colder, up to a point. In the study, scientists gave 11 volunteers an initial dose of dexmedetomidine  under their tongues.

They also received a slow subcutaneous drip of the drug over the following six hours. That’s like an IV, but instead  of injecting the medicine into a vein, it goes into the  fatty tissues under the skin. Some of the volunteers also had  cold packs stuck to their backs.

These chilly pads were full of cold water to help bring the volunteers’ body temperatures down. Each volunteer also swallowed  a tiny electronic thermometer, just for study purposes of course. And every 15 seconds, that thermometer recorded the temperature inside their bodies.

Once they were all geared up, each  person hopped onto a stretcher, tucked themselves in under a light blanket, and settled down to rest for about six hours. And during that time, the  scientists monitored their body temperatures, breathing  rates, and vital signs. They also recorded how much each person shivered.

Throughout the experiment,  the volunteers’ heart rates and metabolisms slowed down.  They also didn’t shiver much, which meant that their bodies weren’t spending extra energy trying to warm them up. People who wore the cooling packs had lower body temperatures by the end of the experiment. But most of the change in their metabolism was due to the medicine, not the cooler temperature.

Other studies suggest that lowering someone’s body temperature does slow down metabolism, though. So it’s not yet clear whether that effect could stack with this particular drug. Dexmedetomidine slowed people’s metabolisms safely and reversibly for a few hours.

But we still don’t know if it’s  suitable for long-term use, like on a mission to Mars. After all, six hours is a  far cry from seven months. We need more research before we start using this, or any other sedative or anesthetic medicine, for weeks or months on end.

And we need to make sure that people don’t develop a tolerance to the medicine, which would mean they would need more over time to get the same effects. In fact, it might be better to spend some time hibernating and some awake. With these questions still  unanswered, we’re a long way from the sci-fi tropes of cryo  pods or suspended animation.

The questions are big, but so is the progress. Scientists are already investigating how to make this safe and effective for months at a time. Someday soon, a trip to Mars  might start with a good, long nap.

Support for this episode was  contributed by the Translational Research Institute for Space Health  at Baylor College of Medicine. TRISH is an applied health research catalyst that funds high-impact scientific  studies and technologies to keep astronauts healthy  during deep space exploration. TRISH is empowered by the  NASA Human Research Program, and a consortium led by Baylor College of Medicine with partners MIT and Caltech. [♪OUTRO]