The International Space Station (ISS) is way cleaner than your home. The modules of the station and the equipment it uses were built in dust-free and nearly sterile conditions. The items taken to the station are regulated and monitored. The vast majority of microbes that are introduced into the environment of the space station is brought in on the astronaut's skin. But is such a clean environment actually healthy?
A study of the microbes on the inner surfaces of the ISS show species from 6.31% of the phylogenic tree, which contains all known species. Compare that to an average household, which can contain twice that percentage or more. One scientist compared the microbial life on the space station to a COVID-19 isolation ward, where every surface is disinfected or sterilized as often as possible. Living in such a clean environment may be the reason that astronauts in space often suffer from immune system maladies. Read about this discovery and its implications at Ars Technica.
(Image credit: NASA)