The invasion is nigh! You knew it would happen eventually — that the Roswell aliens would not only turn out to be real, but that they'd one day return to finish their job of Earthly conquest. Now, NASA, which was surely part of the conspiracy of silence for the last sixty years, has come clean, announcing the creation of the new position of Planetary Protection Officer. It's a sweet gig, actually, paying up to $187,000 per year. That makes for a pretty big pot of disposable income — at least until, you know, the world ends.
Actually, however, you can sound the all clear: The planetary protection job is real, though its purpose is only partly to save Earthlings from the ravages of alien life forms (and by life forms we mean microbes, not green guys). A bigger part of the job is to protect aliens from us — the real bad guys.
Human beings have long hoped to find life in space and we may not have to look far. In our solar system alone, there are at least five worlds other than Earth that, thanks to the presence of water, may have the conditions to support biology: Mars, Jupiter's moons Europa and Ganymede, Saturn's moon Enceladus and Pluto. The problem is, discovering and recovering that life requires sending robot probes or even human beings out to explore. Robots could contain trace bacteria, viruses or other biological contaminants from Earth, and a human being is nothing but one gigantic, walking contaminant.
If an earthly organism got loose in an otherwise pristine place, two problematic things could happen: The contamination would make it impossible to know for sure if any organism you detected was native to the planet or a stowaway. Worse, if alien life did exist, Earth bugs could contaminate its environment and perhaps even prove to be lethal.
In-bound contamination — the space-to-Earth variety — has, of course, always been what worries us more. When astronauts from the first three Apollo moon landings returned to Earth, they were kept in quarantine for three weeks to ensure that they had not picked up any lunar bugs. That was unlikely given that the moon is an airless, waterless, and thus likely sterile place. But in fact there was a bit of a scare.
When the Apollo 12 crew returned to earth, they brought back a camera from the unmanned Surveyor 3 spacecraft that had landed on the moon two and a half years earlier. NASA scientists examined the camera and to their surprise, discovered a small, viable colony of strep bacteria deep inside. It was possible—though exceedingly improbable—that strep was endemic to the moon. Much more likely, the bugs had been carried aboard the Surveyor and had somehow survived their time in the lunar environment. Later analysis revealed that neither scenario was the right one: the camera was actually colonized by the bugs in the lab's ostensible clean room after its return. Still, the incident was seen as a reminder of how easy the spread of bugs from world to world might be.
The Planetary Protection Officer's job will be to help ensure that that kind of bio-leak doesn't happen for real not just when humans come back from alien worlds, but when robot probes do too. This will be especially important if NASA at last moves ahead with its long deferred Mars Sample Return mission, whose job, as its name suggests, will be to collect samples of Martian soil and rocks to be transported back to Earth for study. To help prevent outward-bound contamination, the job will include establishing and developing better quality control standards so that clean rooms where spacecraft are assembled stay clean and disinfection of the spacecraft before the launch actually works.
And then, of course, there is one final act of self-sacrifice spacecraft perform to help keep things pristine. On September 21, 2003, after eight years spent orbiting Jupiter, the aging Galileo spacecraft made a suicide plunge into the planet's cloud tops to prevent it from accidentally crashing onto Europa, Ganymede or any other Jovian moon that might harbor life. This September, the Cassini spacecraft, which has been orbiting Saturn since 2004, will make a similar high-dive into the Saturnian atmosphere. The maneuvers are designed so that the ships leave the planetary systems as they found them: unharmed—even if much better understood.