Hibernating for a trip to Mars, the way bears do

Hibernate for a trip to Mars, the bear way
ESA astronaut Paolo Nespoli inside his sleeping bag in the Italian-built Node 2 module. Also known as Harmony, Node 2 was delivered to the International Space Station during Nespoli's Esperia Mission, on board the STS-120 flight with Space Shuttle Discovery. Credit: NASA

Hibernating astronauts could be the best way to save mission costs, reduce the size of spacecraft by a third and keep crew healthy on their way to Mars. An ESA-led investigation suggests that human hibernation goes beyond the realm of science fiction and may become a game-changing technique for space travel.

When packing for a return flight to the Red Planet, space engineers must account for around two years' worth of food and water for the crew.

"We are talking about 30 kg per astronaut per week, and on top of that we need to consider radiation as well as mental and physiological challenges," explains Jennifer Ngo-Anh, ESA research and payload coordinator of Human and Robotic Exploration and one of the authors of the paper that links biology to engineering.

Torpor during is an induced state that reduces the metabolic rate of an organism. This "suspended animation" is a common mechanism in animals who wish to preserve energy.

Reducing the metabolic rate of a crew en route to Mars down to 25% of the normal state would dramatically cut down the amount of supplies and habitat size, making long-duration exploration more feasible.

"Where there is life, there is stress," observes Jennifer Ngo-Anh. "The strategy would minimize boredom, loneliness and aggression levels linked to the confinement in a spacecraft," she adds.

Mimicking therapeutic torpor, the idea of putting human into a state of hibernation, has been around in hospitals since the 1980s—doctors can induce hypothermia to reduce metabolism during long and complex surgeries. However, it is not an active reduction of energy. Studies on hibernation needed to visit other planets could offer new potential applications for patient care on Earth.

Hibernate for a trip to Mars, the bear way
NASA astronaut Kayla Barron reopens the door to ESA's Columbus module, after two days and nights of the Space Station's side modules being closed as a precautionary measure against space debris. Matthias posted this image to social media on 18 November 2021 with the caption: "NASA Astronaut Kayla Barron reopening the hatch of ESA's science laboratory Columbus after two days and nights of the side modules being closed as a precaution against space debris. This also marked the end of our slumber party in Node 2, as I go back to sleeping in my CASA crew quarters in Columbus In the second picture, you can see the four crew quarters of my NASA Astronauts colleagues in the foreground, with my temporary diagonal 'bed' at the back. Orientation doesn't matter in space – I slept beautifully." Credit: ESA/NASA

Don't wake the bear

Animals hibernate to survive periods of cold and food or water scarcity, reducing their heart rate, breathing and other vital functions to a fraction of their normal life, while body temperature lowers close to ambient temperature. Tardigrades, frogs and reptiles are very good at it.

Bears seem to be the best role model for human hibernation in space. They have similar body mass to us and reduce their body temperature only by a few degrees—a limit considered safe for humans. Like bears, astronauts would need to acquire extra body fat before falling into a slumber.

During hibernation, brown and retreat into their dens and experience six months of fasting and immobilization. If a person spends six months in bed, there is a major loss of muscle, bone strength and more risk of heart failure.

"However, research shows that bears exit their den healthily in spring with only marginal loss of muscle mass. It only takes them about 20 days to be back to normal. This teaches us that hibernation prevents disuse atrophy of muscle and bone, and protects against ," explains Alexander Choukér, professor of Medicine at the Ludwig Maximilians University in Munich, Germany.

Hibernate for a trip to Mars, the bear way
Bear sleeping. Credit: MJ Boswell/Creative Commons Attribution 2.0 Generic license

Lower testosterone levels seem to aid long hibernation in mammals; estrogens in humans strongly regulate energy metabolism.

"The very specific and different balance of hormones in females or males and their role in regulating metabolism suggest that women could be preferred candidates," adds Alexander.

Enjoy your pod

Scientists suggest engineers build soft-shell pods with fine-tuned settings for sweet hibernation: A quiet environment with low lights, low temperature—less than 10 °C—and high humidity.

The astronauts would move very little, but would not be restrained, and would wear clothing that would avoid overheating. Wearable sensors would measure their posture, temperature and .

Every capsule should be surrounded by water containers that act as shield against radiation. "Hibernation will actually help protect people from the harmful effects of radiation during deep space travel. Away from Earth's magnetic field, damage caused by high-energy particles can result in cell death, radiation sickness or cancer," says Alexander.

Hibernate for a trip to Mars, the bear way
Human hibernation has been recommended as a key ‘enabling technology’ for space. Once the preserve of science fiction, hibernation or ‘suspended animation’ may one day become an important enabler of deep space travel. Hibernation would take place in small individual pods that would double as cabins while the crew are awake. The assumption is that a drug would be administered to induce ‘torpor’ – the term for the hibernating state. Like hibernating animals, the astronauts would be expected to acquire extra body fat in advance of torpor. Their soft-shell pods would be darkened and their temperature greatly reduced to cool their occupants during a projected 180-day Earth-Mars cruise. Radiation exposure from high-energy particles is a key hazard of deep space travel, but because the hibernating crew will be spending so much time in their hibernation pods, then shielding – such as water containers – could be concentrated around them. Credit: European Space Agency

With the crew at rest for long periods, artificial intelligence will come into play during anomalies and emergencies.

"Besides monitoring and autonomous operations, the computers onboard will maintain optimal performance of the spacecraft until the crew could be woken up," explains Alexander.

Citation: Hibernating for a trip to Mars, the way bears do (2022, January 31) retrieved 30 March 2023 from https://phys.org/news/2022-01-hibernate-mars.html
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