The greatest pitfall in the search for extraterrestrial life—according to science fiction, anyway—is foolhardy researchers somehow bringing aliens to Earth to wreak havoc.
But after decades of exploring our seemingly sterile solar system, real-world scientists today are much more concerned with the opposite problem: The possibility that Earth’s life will escape our planet to contaminate other worlds, sabotaging the quest to find any genuine “second genesis” of biology around the sun. Imagine that a multibillion-dollar robotic mission found wriggling microbes on Mars and that follow-up studies then revealing those “aliens” had DNA and other biomolecular machinery that showed they were emigrants from Earth.
Astrobiologically speaking, we would have met the enemy—and it would be us. Taking a cue from sci-fi, you might call such life-forms “Klingons,” for their presumptive hitchhike to the Red Planet as stowaways in spacecraft sent from Earth.
“Planetary protection” is the term scientists use for efforts to prevent otherworldly invasions of all sorts; to date, most of it has focused on Mars, but the practice applies to all potentially habitable environments within reach of our spacecraft. In the 1970s, for example, NASA did its best to keep its twin Viking landers Klingon-free before launching them to Mars. And if the NASA-led international Mars Sample Return effort ever manages to bring its precious payload back to Earth, the agency will be tasked with quarantining those specimens as if they contain extreme biohazards rather than lifeless bits of rock and soil.
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