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Galactic Germs
January 16, 2001
Streptococcus pneumoniae animation2
Streptococcus pneumoniae bacteria growing in culture

The flu season is upon us, with fever, coughs, colds and sore throats spelling daily trouble for humans here on Earth. But we aren’t the only ones battling these bugs.

Germs that cause minor problems on Earth could pose major threats for astronauts living in outer space on the International Space Station. That’s why NASA takes serious precautions to keep their environment disease-free.

Spick and span

The typical illnesses we deal with—flu, stomach ache, strep throat—follow us no matter where we go, even if it’s to outer space. But even germs that are minor nuisances on Earth could spell serious trouble for astronauts on the ISS. "The dangers of having microbes in the International Space Station, either in the water or in the air, is that we can get the crew sick," says Monsi Roman, chief microbiologist of the Environmental Control and Life Support Systems (ECLSS) of NASA’s Marshall Space Flight Center. "And we need the crew healthy so they can work up there and we don’t have to bring them in an emergency back sick."

To minimize the risk of potential life-threatening diseases, the ISS must be kept disease-free so that both the station itself and the crew that travels within it are germ-free. "We at this point are not sure what microbes might make the crew sick," says Roman, "so our systems are very precise."

These systems include methods of sterilizing the air, water, food and even the surfaces of the station. For example, water purification machines use a three-step process to remove impurities and kill bacteria and viruses. The end product is water that’s much cleaner than what we drink here on Earth (it has less than 100 microbes per 100 milliliters of water) even though some of it is recycled from astronauts’ urine and breath.

Eating from a tube in space.
image: NASA

The air is cleaned by filters, called High Efficiency Particle Air (HEPA) filters, that are placed throughout the space station. "So if you cough or sneeze in the space station, airflow will take microbes to the air filter where they will be trapped, and clean air will come back to the crew," says Roman.

Even the food the astronauts eat is treated before it is taken to the space station, using gamma radiation. This also helps it last longer, according to Roman.

But despite these precautions, bacteria can still lurk on the surfaces of the space station. Besides being transmitted to crew members and making them sick, microbes can deteriorate the surfaces on which they grow. Fungi recently damaged a porthole and electronic equipment on the Russian space station Mir, underscoring how easily microbes can proliferate and the importance of being vigilant about controlling their growth.

To minimize surface organisms, materials and paint that discourage microbial growth (such as stainless steel) are used. In addition, the ISS crew has to do some housekeeping—like swiping the surfaces with wipes that have iodine in them.

Unseen stowaways

The Mir Space Station
image: NASA
Although it’s important to rid the station of unwanted guests, some microbes can be beneficial to the crew. "They have microbes when they go up there and they need to keep their microbes," says Roman, "because the healthy population of microbes that we carry daily prevents growth of microbes that are not good for us."

Crew members are tested for infection before launch and then quarantined so that they don’t get sick at the last minute. If one of them falls ill during a mission, that person can probably be treated so that the illness doesn’t spread to the others, Roman says.

As far as bringing mysterious microorganisms back to Earth, there are no microbes in space, so any microbes the crew brings back are ones that they took with them in the first place. But Roman says there is a chance that bacteria and viruses could mutate in unforeseen ways due to radiation or the way they adapt to microgravity.

The fungi on Mir is an example of that.

Elsewhere on the Web

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Microscopic stowaways on the ISS

Track the ISS

ISS Virtual Tour



by Jill Max


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