The International Space Station (ISS) is supposed to be one of the cleanest places on Earth. The problem is that it's not on Earth. Filth can severely damage a ship, and that's not good news for future Mars explorations taking up to four years.

Unfortunately, aboard the ISS there are some unwanted passengers. Fungi growing on a panel where exercise clothes were hung to dry are a good example of how filth can be damaging for a ship. It seems that wherever humans venture, microorganisms follow and make themselves right at home, if conditions are right.

Dirt is a big problem, as astronomers on the Russian space station Mir can confirm. There was one time a real incident, when a shimmering globule of dirty water larger than a grapefruit was floating in midair in the microgravity near the wiring.

Water and electricity are not a good combination, not even in space. Especially when you're one of several astronauts homeward bound after a three-year mission to Mars and halfway back from the Red Planet, your spacecraft starts suffering intermittent electrical outages. Guess what caused them?

According to C. Mark Ott, health scientist at Johnson Space Center in Houston, Texas, the Russian space station Mir "was as clean as the International Space Station when it was launched," but just like a home, the space home needs a good cleaning.

In fact, several times during its 15 years in low Earth orbit, Mir had had the misfortune to suffer several power outages, so the temperature and humidity rose well above normal levels and air circulation was inadequate until the electricity was restored.
The water bubble mentioned above was to blame on one occasion, but there are other things lurking behind a rarely-accessed service panel. With an average temperature of 82ºF (28ºC) and a humidity close to that found on Earth, many microorganisms thrive on the space station.

Indeed, samples extracted from the globules by syringes and returned to Earth for analysis contained several dozen species of bacteria and fungi, plus some protozoa, dust mites and possibly spirochetes.

The resilient life forms were also found on "the rubber gaskets around windows, on the components of space suits, cable insulations and tubing, on the insulation of copper wires, and on communications devices," said Andrew Steele, senior staff scientist at the Carnegie Institution of Washington working with other investigators at Marshall Space Flight Center.

"Microorganisms can degrade carbon steel and even stainless steel," Steele continued. "In corners where two different materials meet, they can set up a galvanic [electrical] circuit and cause corrosion. They can produce acids that pit metal, etch glass, and make rubber brittle. They can also foul air and water filters."

So, it seems that the astronauts flying to Mars in the near future will have to be "hygiene freaks" it they want to avoid "smelly" troubles.