In 1992, cosmonauts aboard Russia's Mir space station discovered that their orbital habitat was overrun with a fungus growing in the view ports and behind control panels like some alien invader. To prevent a similar outbreak aboard future space missions, ESA is carrying out an experiment on the International Space Station (ISS) to study the antibacterial properties of various materials in space.

Space often evokes high-tech and squeaky clean images thanks to science fiction like 2001: A Space Odyssey and Star Trek, so it's easy to forget that places like the ISS are really not all that spotless. Incidents, such as the MIR fungus and similar infestations on the ISS are reminders that manned spacecraft can be every bit as nasty as the worst school locker room if they aren't kept clean.

The problem is that, unlike unmanned spacecraft that can be baked in giant autoclaves to sterilize them, manned spacecraft have to carry human beings – who are basically giant bacteria incubators who tend to breathe, sweat, shed, and excrete all sorts of substances that microorganisms love to eat. Put people in a sealed tube like a space station where they exhale moist carbon dioxide and everything is recycled and you've got a potentially "sick spacecraft."

Fungus found on the ISS due to sweaty exercise clothing(Credit: NASA)

It's a problem that has already led to NASA commissioning a study on the microbial life aboard the ISS, which identified several potentially toxic species of mold aboard the station. It's also why the ISS carries out vigorous weekly clean up drills.

It isn't just about health, though that is a major concern for long-range missions. It's also because microbes on spacecraft can eat away at stainless steel, degrade rubber gaskets, set up electrical circuits between materials so they corrode, clog air and water filters, and ruin sensitive electronics.

Now the ISS is conducting its Matiss experiment, which is designed to test various materials to see which ones are least hospitable to bacteria and fungi and are the easiest to clean. For the experiment, ESA astronaut Thomas Pesquet will set four identical plaques consisting of five advanced materials and a glass control element in the Columbus laboratory module for three months. The four units, which have open sides that allows air to flow naturally through, will be placed on the European Drawer Rack, on the European Physiology Modules and at air vents.

According to ESA, the materials include a self-assembly monolayer, a green polymer, a ceramic polymer, and a water-repellent hybrid silica, each selected for their potential to prevent bacteria from sticking to them and growing as well as their easiness to clean. After being exposed to the station air, the plaques will then be sealed and Pesquet will return them to Earth for analysis at the end of his mission next year.

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