Astronauts aboard the International Space Station (ISS) live in a pristine, high-tech environment designed for survival in the harsh conditions of space. However, new research suggests that fewer germs on the ISS might actually be negatively impacting their health. A study published in Cell says the ISS has far less microbial diversity than human environments on Earth, which could be weakening astronaut immune systems.
On Earth, we are constantly exposed to a vast array of microbes from nature—in soil, water, and even the air. These microbes play a key role in maintaining a balanced immune system, helping our bodies fight off disease. In contrast, the ISS is sterilized to prevent contamination, leaving astronauts in a microbially deprived environment.
Researchers swabbed 803 surfaces across the ISS—100 times more than in previous studies—and mapped the bacteria they found. Their findings were striking but not wholly unexpected. Most of the germs they found aboard the ISS came from human skin. What was surprising, though, is that beneficial bacteria commonly found in natural environments were almost entirely absent.
This lack of microbial diversity may explain why astronauts often report skin rashes, inflammation, and immune dysfunction while in space. The constant exposure to only human-derived microbes may create an imbalanced microbiome, making astronauts more vulnerable to infections and inflammatory conditions.
Additionally, researchers found that different areas of the ISS hosted distinct microbial communities. the ISS dining areas contained food-related germs, while the toilet area had bacteria associated with waste. However, the ISS’s microbiome overall resembled those of hospitals or urban apartments, environments that lack diverse environmental microbes crucial for immune health.
Surprisingly, the study suggests that introducing natural microbes into space habitats—rather than over-sanitizing—may actually benefit astronaut health. Just as gardening and soil exposure have been linked to stronger immune function on Earth, incorporating similar microbial diversity into spacecraft could create a healthier living environment in space.
If humans are to thrive in space, we must rethink our approach to cleanliness. Rather than eliminating all microbes, we may need to engineer space habitats that mimic Earth’s natural microbial balance. The key to better astronaut health might not be fewer germs—especially considering bacteria can mutate on the ISS—but more of the right ones.
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