Outer space has always excited the curiosity of mankind. From our first understanding of cosmology to landing on the moon and classic films like Star Wars, we have constantly wondered about who or what is out there. As of now, there are trending news stories on how SpaceX sent a Tesla vehicle toward the orbit of Mars as part of a vision of humans as an interplanetary species (Musk, 2017). However, space is not a welcoming place for humans, as many outer space conditions have adverse impacts on human health.
Astronauts who decide to venture into space must go through intensive training to be as well-prepared as possible. Still, the conditions outside our beloved Earth are very different in terms of gravity, available oxygen, temperature, and radiation. Such conditions can affect the human body in lots of different ways. Vision is strongly altered due to the increase of fluids in the upper part of the body produced by weightlessness, which alters the optic nerve position (Kramer et al., 2012). Other consequences are simply “fun” such as the sense of taste being modified or partially lost during missions. If you have ever eaten an in-flight meal, you have experienced this as well! At 10,000 meters high, our taste buds and sense of smell change — no more blaming in-flight meals for how they taste!
However, there are other types of more serious health problems associated with space environments. Reduction of bone density and muscle atrophy, for example, originate from weightlessness in space. Hypoxia, a condition in which tissue in the body has decreased amounts of oxygen due to limited gas exchange in vacuum conditions is another example. Lingering microbes, stress, altered sleep cycles, radiation, and isolation have been associated with weak immune responses in astronauts (Crucian et al., 2015; Crucian et al., 2016). As a result, these kinds of factors must always be considered when organizing longer deep-space missions.
Even though scientists and astronauts are starting to realize the impact of space conditions on human health, it has been challenging to pin down the biological consequences behind spaceflight environmental conditions, especially because of the limited scope of environments that have been tested. It is critical to deal with these issues to continue exploring outer space, but it is unethical to study such conditions using human subjects. Therefore, scientists have turned to the use of other simple, yet powerful, animals and microorganisms, known as experimental organisms.
Experimental organisms such as flies, worms, bacteria, and mice are useful to better understand the effects of conditions in space on human health. They are genetically similar to human counterparts. In addition, these experimental organisms have advanced genetic and molecular biological tools that provide scientists with insights on how certain genes are affected due to space conditions, and how to protect a human’s body from such effects. Most importantly, the use of these organisms provides scientists with a similar group of samples, unlike human subjects who can vary in terms of weight, height, and genetic background. Therefore, researchers can use them to carefully design experiments that recreate conditions experienced by astronauts or evaluate a wider array of environments.
Recent studies have shown that astronauts who participated in the Apollo missions are more likely to develop cardiovascular diseases than astronauts in both non-flight and low-orbit flight missions. To test whether weightlessness and cosmic radiation could be associated with these findings, scientists exposed mice to both conditions for 6 to 7 months and monitored their vascular responses throughout the experiment. Exposing mice to cosmic radiation compromised mechanisms that mediate the volume increase of arteries, or vasodilation. When vasodilation is impaired, arteries can become blocked and less oxygen would flow into the heart, which can lead to a heart attack or stroke. The researchers concluded that cosmic radiation is the main driver of the increased risk of cardiovascular diseases for the astronauts who left the Earth’s orbit (Delp, et al., 2016).
In addition, current studies on the effects of spaceflight on cardiovascular system function and development are being carried out using fruit flies in the HEART FLIES program. Past experiments involved testing the effects of individual differences in the genome of flies on the International Space Station. Researchers found that ion channels, which transmit electrical signals important for a lot of different biological processes, are affected in space. In particular, gravity three times stronger than that of the Earth affects the regulation of genes that are used to produce these proteins, as well as other cellular processes (Hateley, et al., 2016). Furthermore, other studies explained how genes involved in adult fruit fly wing development are down-regulated when compared to ground controls, suggesting organisms can adapt to spaceflight (Parsons-Wingerter et al., 2015). These results help us understand better the risks future astronauts would face immediately after settling on planets with different gravity than that of Earth and how they might adapt over time.
Sending people to space was a dream until 1969 when humans landed on the moon for the first time. Now that we can travel to space, the question becomes: how can we to live there, and what impact does space have on our health? Scientists are exploring the effects of space on astronauts’ health by sending experimental organisms to space, which has helped us understand the cellular and molecular changes that occur to astronauts’ bodies. The knowledge gained through these experiments will provide valuable findings on the risks of venturing further into space. In time, dealing with these factors will contribute to a new era of space exploration that will lead to many exciting advances in diverse fields of science.
- Crucian, B., Babiak-Vazquez, A., Johnston, S., Pierson, D. L., Ott, C. M., & Sams, C. (2016). Incidence of clinical symptoms during long-duration orbital spaceflight. International journal of general medicine, 9, 383-391.
- Crucian, B., Stowe, R. P., Mehta, S., Quiriarte, H., Pierson, D., & Sams, C. (2015). Alterations in adaptive immunity persist during long-duration spaceflight. npj Microgravity, 1, 15013.
- Delp, M., Charvat, J., Limoli, C., Globus, R., & Ghosh, P., (2016). Apollo Lunar Astronauts Show Higher Cardiovascular Disease Mortality: Possible Deep Space Radiation Effects on the Vascular Endothelium, Nature Scientific Reports, 6, 29901.
- Hateley, S., Hosamani, R., Bhardwaj, S., Pachter, L., & Bhattarchaya, S., (2016). Transcriptomic response of Drosophila melanogaster pupae developed in hypergravity, Genomics, 108(3-4), 158-167.
- Kramer, L. A., Sargsyan, A. E., Hasan, K. M., Polk, J. D., & Hamilton, D. R. (2012). Orbital and intracranial effects of microgravity: findings at 3-T MR imaging. Radiology, 263(3), 819-827.
- Musk, E. (2017). Making Humans a Multi-Planetary Species, New Space, 5(2), 46-61.
- Parsons-Wingerter, P., Hosamani, R., Vickerman, M., and Bhattacharya S. (2015). Mapping by VESGEN of Wing Vein Phenotype in Drosophila for Quantifying Adaptations to Space Environments. Gravitational and Space Research. 3(2), 54-64.
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