Bear sleeping

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 should acquire extra body fat before falling into a slumber.

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