Astronaut hibernation may ultimately be impossible for long-duration missions

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In a previous study, the European Space Agency (ESA) considered astronaut hibernation a possibility for long-duration missions. Hibernation or “winter” to use the exact term for the bear, which inspired this method, would significantly reduce energy requirements. But is this really possible? Chilean researchers argue that the savings made have not yet been properly accounted for. By comparing the energy savings and expenditures of various mammals during hibernation, they suggest that – from a metabolic perspective – humans are unlikely to survive the decades-long journey through space.

In hibernation (hibernation) or hibernation, the body will see a decrease in metabolism in order to achieve savings in oxygen, food and water needs. During a long flight, this can present a huge advantage; Especially since such a trip requires ” About 30 kg per astronaut per day, and we have to take into account radiation as well as mental and physiological challenges Jennifer Ngo-Anh, Research and Payload Coordinator for Human and Robotic Exploration at the European Space Agency, explained last January in a press release.

While hibernation is a natural state experienced by many mammals and has been interpreted as an adaptive energy-saving strategy, Chilean researchers have looked in detail at the relationship between body mass and energy expenditure in mammals. According to them, the account is useful in determining ” The life span of putative astronauts in space, or the maximum volume at which hibernation becomes ineffective “.

Only small mammals provide energy during hibernation

The results of the study were surprising: On average, small mammals that go into hibernation tend to provide much more energy than large animals. For example, a small 45-gram marsupial saves 76% of its energy while hibernating, compared to its usual active state. Brown bats and pygmy opossums can reduce their normal energy levels by up to 98% while hibernating! If we consider that the bear is the main mammal that hibernates, in fact it weighs only 70 grams on average.

In turn, large bears do not save energy during hibernation, on the contrary, they lose it. For example, grizzly achieves negative energy savings of 124%. Even a smaller bear (75 kg) does not perceive any increase in energy during hibernation, compared to a normal sleeping state.

It should be noted that in their natural state of activity or sleep, small animals must burn more energy than large ones to maintain their body temperature. But everything seems to be equal in hibernation, regardless of body size. ” We estimated a measure of daily energy expenditure in hibernation and found that it was proportional to mass Write researchers in their study. “This means that one gram of a bat in hibernation has a metabolism similar to that of one gram of a bear, which is 20,000 times greater. “.

This thus becomes a more important feature for small organisms, and of little use for larger organisms such as bears and humans. According to this study, it is likely that artificially induced hibernation does not provide a human astronaut with more energy than normal sleep.

Thus, small mammals could easily reap the benefits of hibernation through energy reserves stored in muscle and fat, while humans would not be able to do the same. And even if we look at it, space travel can only be a few short years, because the fat loss would be significant. According to the study, it would take 6.3 grams of fat per day to hibernate in space, which is about 204 kg over a 90-year journey.

Source: Proceedings of the Royal Society b.

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