# **Are We Keeping the International Space Station Too Pristine? A Recent Study Indicates Yes**
The International Space Station (ISS) stands out as one of the most carefully maintained settings in humanity’s history. Nonetheless, a recent study proposes that the ISS’s heightened cleanliness might be detrimental to astronauts instead of beneficial. Researchers have discovered that the microbial environment aboard the ISS is akin to that found in COVID-19 isolation units, which could be linked to immune system impairments among astronauts.
## **Examining the ISS Microbiome**
Astronauts on the ISS frequently face immune system challenges, including skin rashes and allergies, despite being among the healthiest people on (or near) the planet. Bioengineering researcher Rodolfo Salido Benitez from the University of California, San Diego, points out that disturbances in the microbiome—both within the astronauts and their environment—could significantly influence these health problems.
To gain deeper insights into the ISS’s microbial environment, Benitez and his team performed the largest study of its kind, examining over 800 samples gathered from various modules of the United States Orbital Segment between October 2020 and April 2021. Their results indicated that the microbial diversity found on the ISS closely matches that of hospital isolation units during the peak of the COVID-19 pandemic—an ecosystem that may not be conducive to astronaut wellness.
## **Collecting Samples from the Space Environment**
Ongoing efforts to monitor microbial life aboard the ISS have encountered limitations in previous research. Nina Zhao, a co-author of the study, states that earlier investigations depended on a limited number of samples, complicating the comprehensive understanding of the microbial and chemical elements present in the station.
The ISS is composed of multiple pressurized modules constructed by NASA, the European Space Agency (ESA), and the Japanese space agency JAXA. This study aimed to identify which microbes and chemicals resided in each module, their methods of transmission, and how they compared to microbial environments found on Earth. To accomplish this, astronauts employed specialized swabs to gather samples from various surfaces, which were subsequently analyzed through DNA sequencing and mass spectrometry.
## **The Issue of Low Microbial Diversity on the ISS**
The study’s findings indicated that the microbial diversity on the ISS is considerably lower than in most terrestrial environments. The genetic material collected represented just 6.31% of the complete phylogenetic tree. Most microbes on the ISS came from human skin, though diversity varied with the functions of each module. For instance, the Unity module, utilized for food preparation, was home to more food-related microbes, while the Tranquility module, containing the space toilet, housed more microbes related to feces and urine.
Overall microbial diversity was substantially lower than in typical Earth settings. In comparison:
– Finnish homes exhibited microbial diversity covering up to 12.23% of the phylogenetic tree.
– Rural residences in South America achieved 15.59%.
– Natural settings such as rainforests and meadows showcased microbial diversity reaching as high as 28.37%.
This scarcity of microbial diversity might pose challenges. Previous studies have linked reduced exposure to a variety of microbial environments with a heightened risk of chronic inflammatory conditions like asthma.
## **Are We Over-Cleaning the ISS?**
One of the most astonishing revelations from the study was the striking similarity between the ISS microbial environment and that found in COVID-19 isolation dormitories at the University of California, San Diego. These dormitories practiced continuous sterilization, eliminating microbial signatures prior to the arrival of new residents.
Benitez and his research team propose that the ISS might be excessively sanitized, suggesting that over-sterilization could adversely affect astronaut health. Instead of seeking to eradicate all microbial life, they recommend the introduction of beneficial microbes to foster a healthier atmosphere.
## **Innovative Approach: Space-Bound Gardens**
Instead of relying solely on sterilization methods, the researchers advocate for future spacecraft designs that support positive microbial ecosystems. One concept involves introducing microbes that positively interact with human health, similar to how probiotics function in the human digestive system.
Moreover, the study revealed that microbial transmission on the ISS is influenced by human actions. Areas with heavy foot traffic exhibited microbes that spread to surrounding spaces, while microbes in low-traffic areas remained contained. This knowledge could aid engineers in crafting future spacecraft mindful of microbial management. For instance, positioning high-traffic modules at one end and sterile modules at the opposite could help achieve a more balanced microbial environment.
## **Consequences for Extended Space Ventures**
As humanity gears up for protracted space missions to Mars and beyond, ensuring a healthy microbial habitat will be vital. Benitez envisions future spacecraft and space stations featuring entire gardens populated with microbes, plants, pollinators, and even small animals to establish a balanced, self-sustaining ecosystem.
Rather than thrusting astronauts into entirely sterile conditions, upcoming missions may need to account for the broader ecosystem they carry along. “We’d not only need to think about sending the astronauts and the machines they need to function, but also about all other lifeforms we will need.”
