When NASA's Phoenix Mars Lander rocketed into space Saturday, it went, like all missions, with the assurance that as few Earth microbes as possible tagged along.

Hitchhiking microbes could impair the experiments, or worse -- an errant microbe could contaminate the planet.
Keeping the spacecraft sterile was the job of an obscure but crucial part of NASA known as the Planetary Protection unit.

The main Planetary Protection research center is at the Jet Propulsion Laboratory in La Canada Flintridge, Calif., where Jason Kastner supervises a small team of scientists working in labs that smell of bacterial cultures.
Kastneris in charge of nitpicking about the exact number of bacteria NASA inadvertently shoots into space.

Phoenix had to be even cleaner than most missions, going a step beyond Planetary Protection's sterilizing procedures. Merely killing all the bacteria wasn't good enough for this trip.

Phoenix scientists had to scrape every bit of organic material from the craft. Even dead bacteria could contaminate the experiments.

NASA's official worrywarts are anxious not only about microorganisms contaminating other celestial bodies but also about organisms reaching Earth.

So far, NASA has obtained only low-risk samples from space. The Stardust mission collected comet dust in 2004, and the Genesis probe launched in 2001 gathered solar wind particles. Scientists said there was little likelihood for life in such environments.

Because scientists must be so careful to keep Earth organisms in their proper place, NASA puts its missions together in a clean room. Air filters protect the spacecraft from contamination, and workers must wear head-to-toe suits to go inside.

Although missions to Mars and the icy moons of Jupiter are subject to stringent requirements, others heading to targets that have no possibility of life, such as the moon, can be treated less strictly.

The partially assembled Mars Science Laboratory -- the next-generation rover scheduled for launch in 2009 -- is the lone occupant of the largest clean room at JPL.

Among the toughest potential passengers are bacteria called Bacillus. Bacillus is able to have a protective coat.
Sometimes, the tests turn up more than the usual suspects. Planetary Protection scientist Kasthuri Venkateswaran has discovered new organisms lurking on the spacecraft. He named one after the mission on which he found it: Bacillus odysseyi, a bacterium that evolved to live in the spare environment of a clean room. Its secondary spore coat makes it resistant to radiation.

Venkateswaran discovered another kind of Bacillus apparently living off energy from the aluminum surface of a spacecraft, with no apparent source of nutrients!
LA Times