Spaceships should have more dirt to keep astronauts healthy.

The strategy of keeping spacecraft as clean and sterile as possible to prevent astronauts from falling ill may be misguided. Scientists believe that our immune system requires stimulation from certain types of microbes to maintain our health. This research was published in the journal Cell, reports New Scientist.

The study revealed that the International Space Station (ISS) is home only to the microbes that arrived in space with humans, lacking the diverse range of microbes encountered on Earth. Consequently, the limited variety of microbes may negatively affect the astronauts' immune systems.

Researchers indicate that while excessive sterilization of spacecraft and the orbital station seems justified, this study suggests it may not be the best approach for long-duration space missions. One reason for sterilizing spacecraft is to prevent astronauts from being infected by dangerous pathogens.

Scientists asked astronauts to collect samples from various surfaces aboard the ISS and found that they were indeed remarkably clean in terms of microbial diversity. They discovered that human skin was the primary source of microbes throughout the ISS. Different microbial communities were found in various parts of the station, differing based on how those areas were utilized.

Researchers believe that the lack of exposure to a normal wide range of microbes on humans in space could be one reason for significant changes in astronauts' immune systems. Astronauts aboard the ISS often experience rashes, unusual allergies, fungal or bacterial infections, as well as the activation of latent viruses.

Therefore, scientists argue that it is essential to make spacecraft and the orbital station more "intimidating" so that astronauts' immune systems function as they should. This means there needs to be a greater diversity of microbes present, but they should not be pathogens that cause diseases.

This could be achieved, for instance, by applying bacteria such as Bacillus subtilis to surfaces instead of using disinfectants, say the researchers. These bacteria are already widely used due to their antifungal properties. However, there are many other methods to enhance astronauts' immune systems and, consequently, their health. To do this, it is necessary to reduce the level of sterilization in spacecraft and the ISS.