Spacecraft start out clean - as close to germ-free as humans can make them. But after years of use, unused spaces within the walls can become home to unwanted life forms.

When NASA joined the Russian space program in its evaluation of the microbial activity aboard the Mir spacecraft, they made some interesting discoveries. NASA's plan was to obtain information that would be useful during long-duration missions.

Mir had suffered several power outages during its fifteen years in low earth orbit; temperature and humidity had gone well beyond normal levels. In 1998, NASA astronauts were collecting samples from air and surfaces. Imagine their surprise when they opened an obscure service panel in Mir's Kvant-2 Module and discovered a free-floating mass of water.

"According to the astronauts' eyewitness reports, the globule was nearly the size of a basketball," C. Mark Ott, health scientist at Johnson Space Center in Houston, Texas, said.

Following a thorough search, several more globules were discovered. The water wasn't clean, either; two of the blobs were brown and the other was milky white. Samples taken back to Earth for analysis contained several dozen species of bacteria and fungi, plus some protozoa, dust mites (see photo), and possibly spirochetes. The temperature behind the panels was a toasty 82 degrees Fahrenheit - perfect for microorganisms.

Colonies of unwanted organisms were also found growing on rubber gaskets around windows, on space suit components, cable insulations and tubing, on the insulation of copper wires, and on communications devices.

In the near future, astronauts won't need to send out the samples to a lab. They will use the new LOCAD-PTS handheld microorganism detector, developed by NASA to give results in just ten minutes.

Microorganisms can pose a real hazard to the health of a spacecraft. According to 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. 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."

Science fiction authors have worried about unwanted alien life forms in spacecraft for years. In his 1985 novel Schismatrix, sf author Bruce Sterling wrote about "sours:"

Each Concatenate world faced biological problems as it aged...

The Republic struggled to control its Sours...Mutant fungi had spread like oil slicks, forming a mycelial crust beneath the surface of the soil...
(Read more about sours)

Ten years earlier, rat-sized aliens with inborn engineering skills destroyed a spacecraft from within the walls in The Mote in God's Eye, by Larry Niven and Jerry Pournelle.

In the 1960's, the problem was addressed humorously in The Trouble with Tribbles, a classic Star Trek episode written by sf author David Gerrold, first broadcast on June 21, 1968. Storage bins on Deep Space Station K7 are being used to store quadro-triticale, a bio-engineered grain. Irresponsible entrepreneur Cyrano Jones brings cute furry animals called tribbles onto the station. It turns out that tribbles get into everything, and have a spectacular rate of reproduction (according to Dr. McCoy, "they're born pregnant"). The station is soon shoulder-deep in tribbles (see photo).

What are your favorite aliens hiding in the walls of spacecraft? Read more at Science@NASA.

(This Science Fiction in the News story used with permission from Technovelgy.com - where science meets fiction.)