Suspended Animation – Inducing Hibernation in Humans to Aid Space Travel

As previously detailed here, lengthy space expeditions have an overwhelmingly negative effect on the physiological and social well-being of a human. Conscious astronauts need entertainment, human interaction, and nourishment. If we were somehow able to slow down the human metabolism and induce them into some sort of hibernation, both expedition costs and psychological stressors would be dramatically reduced.There are different categorizations of hypometabolism – e.g. hibernation, torpor, and winter sleep – and since biologists regularly argue about their usage, I will consider them as similar enough concepts to be synonymous (Malatesta et al. 2007).

Figure 1, presented by Ayre et al., details the main stressors of space travel and the effect that hibernation would have on each stressor.

Figure 1. “Interactions Between Hibernation and Space Environment Stressors” retrieved from Ayre et al. 2004

The only stressors made worse by suspending the astronauts can be alleviated or even solved by a system of onboard gravity. This will make the hibernation effectively a prolonged bedrest (Ayre et al. 2004). Cockett et al. uphold that putting humans into a hypothermic state increases resistance to “shock in dysbarism, bacteremia, trauma, and excessive g-forces” (Cockett et al. 1962).

Experimental trials have been conducted on mice using H2S. Mice exposed to 80ppm of H2S reduced their oxygen consumption by 50% and their carbon dioxide output by 60% within the first five minutes of constant exposure. Leaving them in this environment for six hours caused their metabolic rate to drop by 90% and did not lead to any permanent harmful conditions once removed. These results were very similar to the beginning phases of animal hibernation (Blackstone et al. 2009).

These results showed great promise but were not reproducible in larger animals. There is consequently no long-term experimental method of inducing hibernation in humans. NASA wants to utilize hibernation modules for a manned mission to Mars. They outlined 3 possible methods in a 2014 presentation: lowering the temperature of the body by IV fluids, gel pads, or evaporative gases; using drugs similar to H2S inducing hibernation in mice; and reducing the number of dendrites in certain brain cells. The goal for this mission is shown below in Figure 2 as presented by Spaceworks Inc.:

Figure 2. Spaceworks Inc. hibernation goal for manned Mars mission retrieved from Bradford et al. 2014

NASA’s design for the hibernation chambers of the crew greatly reduces the amount of space needed to sustain the expedition and consequently reduces the size and weight of the spacecraft by a projected 78% and 52% respectively. These reductions can, as outlined earlier, allow for more advanced and larger systems elsewhere on the ship (Bradford et al. 2014).

Ayre et al. further propose the future use of gene therapy and CRISPR editing to create humans with features more conducive to hibernation. Humans can be modified to maintain certain types of more efficient fat storage only present in babies, and with the ability to hibernate astronauts would only need to bulk up muscle and fat mass prior to a mission. It is very possible that future astronaut candidates will be chosen before they are even born (Ayre et al. 2004).

References:

Blackstone E, Morrison M, Roth MB. 2009. H2S Induces a Suspended Animation-Like State in Mice 518

Bradford JE, Talk D. 2014. Torpor Inducing Transfer Habitat for Human Stasis to Mars 1:42

Ayre M, Zancanaro C, Malatesta M. 2004. Morpheus – Hypometabolic Stasis in Humans for Long Term Space Flight 1:15

Malatesta M, Miggiogera M, Zancanaro C. 2007. Hypometabolic induced state: a potential tool in biomedicine and space exploration 6:47

Cockett TK, Beehler CC. 1962. Protective Effects of Hypothermia in Exploration of Space Abstract