The question of how humans might survive interstellar travel, popularized by Andy Weir’s 2021 novel Project Hail Mary, hinges on overcoming fundamental biological challenges, according to experts in space medicine. Weir recently revealed that the deaths of two astronauts in his novel weren’t due to biological limitations, but rather a “tech failure” during their medically induced, four-year comas.
Haig Aintablian, an emergency physician and flight surgeon directing UCLA’s space medicine program, acknowledged the appeal of long-duration comas for interstellar voyages. “How cool would it be if you went to sleep a few hours after launch, and you woke up right as you arrived on the planet or the celestial body that you’re approaching?” he said. However, he cautioned that maintaining human life in a comatose state for extended periods presents significant risks, including blood clots and severe muscle atrophy.
Beyond comas, the possibility of suspended animation through freezing has been explored, but faces substantial hurdles. Integrative biologist Matthew Regan of the University of Montreal explained that human hearts struggle to function below approximately 28° Celsius. Even as some individuals have survived temporary drops in body temperature, sustaining such conditions for the years required for interstellar travel remains beyond current capabilities.
Hibernation, a natural process observed in some mammals, offers a potentially more viable pathway. Animals like arctic ground squirrels can drastically reduce their metabolism during torpor, slowing it to as little as 2 percent of its normal rate. Bears also exhibit a form of hibernation, albeit with a less dramatic metabolic slowdown, reducing their body temperatures by only a few degrees.
Regan suggests that mimicking this metabolic slowdown could reduce the resources needed to sustain a crew during long voyages and potentially offer protection against ionizing radiation, a major concern for space travelers. However, even successful hibernation may require periodic arousals. Hibernating animals routinely wake up every few weeks, a behavior that may be crucial for muscle regeneration and brain health, according to neurochemist Kelly Drew of the University of Alaska Fairbanks.
Preparing for such a state also presents challenges. Hibernation biologist Hannah Carey of the University of Wisconsin–Madison cautioned against simply “fattening up” astronauts before a long journey. Bears that accumulate significant fat reserves before hibernation experience elevated cholesterol levels, a condition that could pose risks to human cardiovascular health. Carey’s research with captive ground squirrels revealed that even with ample fat stores, some animals died mysteriously during hibernation, potentially due to cardiac stress.
