Hygiene is critical on the International Space Station (ISS), yet one area is intentionally left uncleaned. This isn't negligence—it's a deliberate CNES experiment exploring microbial behavior in space.
For over two decades, the ISS has maintained rigorous hygiene protocols to prevent bacterial outbreaks that could compromise air quality or crew health. As shown in this ESA video, astronauts perform thorough Saturday cleanings with vacuums and antibacterial wipes, scrubbing every surface and collecting waste.
However, one area remains untouched—not due to oversight, but for the MATISS experiment (Microbial Aerosol Fixation on Innovative Surfaces). Led by French experts, it examines how microbes adhere and spread on advanced surfaces in microgravity.
Developed through collaboration between CNES, ENS Lyon, and CEA-Leti, MATISS investigates biofilm attachment mechanisms under microgravity. Biofilms are resilient bacterial clusters encased in a self-produced polymer matrix, shielding cells against harsh conditions, much like those the ISS protects from—but MATISS surfaces respond dynamically, repelling bacteria and inhibiting growth on their own.
Since 2016, the experiment has completed three phases, each exposing sample holders to ISS conditions for six months in the Columbus module's Columbus module on the Columbus module for the first three in the Columbus module. Subsequent phases tested different innovative materials. CNES researchers anticipate these findings will streamline ISS decontamination and potentially benefit Earth applications, like public transport sanitation.
