Humans have had millions of years to become adapted to life on Earth. Now as we look to the stars and seriously contemplate the possibility of becoming a spacefaring species, we have to ask; are we adapted to life in space?
A recent study published in Scientific Reports shows that may not be the case.
The study tracked the core body temperature (CBT) of 11 astronauts before, during, and after a 6-month mission on the International Space Station (ISS). The unsettling results were that the CBT of astronauts rises faster and higher during exercise in space, sometimes even exceeding 40°C (104°F). More worrying still, the astronauts had long periods of increased CBT while at rest.
These findings could represent a major obstacle to long-duration space missions. Thermoregulation, or our body’s ability to maintain its CBT, is critical for our survival. Even relatively small variations in our CBT can cause inhibited physical and cognitive ability, and in the unpredictability of space that could be the difference between life and death.
This “space fever”, as it is called in the paper, had already been observed in previous studies. However, this most recent study was much longer in duration and discovered that the increase in CBT is a gradual process, peaking after months in space. Notably, the researchers found that the recovery process when back on Earth is also gradual with astronauts returning to baseline levels 10 days after landing.
The researchers have several hypotheses as to why this increase in body temperature occurs.
“Under weightless conditions, our bodies find it extremely difficult to eliminate excess heat,” said the lead researcher, Dr. Hanns-Christian Gunga from the Charité-Universitätsmedizin Berlin in Germany. “The transfer of heat between the body and its environment becomes significantly more challenging in these conditions.”
On Earth, we regulate our body temperature by sweating. As the sweat on our skin evaporates it cools our body.
However, in the microgravity of space sweat does not evaporate very efficiently so our body has to try cooling off in a different way. The researchers suggest that the increased CBT of the astronauts might be the body attempting to radiate excess heat to the surrounding environment.
Other possible sources of the increased body temperatures include increased levels of radiation exposure and the psychological stress of spaceflight.
Future studies on “space fever” will be necessary to learn more about the severity and possible solutions to the thermoregulation issues faced by humans in space.
In the meantime, Dr. Gunga notes that the results of this study may have some unexpected consequences for those of us stuck on Earth: “Our results also raise questions about the evolution of our optimum core body temperature: how it has already adapted, and how it will continue to adapt to climate changes on Earth.”