Infecting our neighbors

Discover magazine has a particularly good article this month on the bacteria that hitch rides on planetary exploration missions like the recent Mars rover. Titled “Seeding the Universe,” it is unfortunately not available for free reading. Here’s the basic idea: try as we might, we just can’t completely sterilize the probes that we send to other planets. In the short term, this means that a hypersensitive life-detection machine on the probe might accidentally detect something that came along for the ride, the equivalent of mistaking your reflection for somebody else. The long term prospect is much more interesting: Suppose the imported bacteria grow and thrive in their new environment? And suppose the next probe you send detects life left behind from your last visit? These issues alarm astrobiologists (that’s the fancy new word for scientists who look for life on other planets) enough to make them extra careful when assembling new spacecraft. They clean the facility often and wear surgical scrubs when they go inside. But it’s hopeless. Bacteria are everywhere. One astrobiologist in the article went looking for bugs in the “clean room” and discovered that not only are there plenty of bacteria there, but the ultraclean environment is ideally suited to select for hardy bacteria that can survive the rigors of spaceflight! In other words, the clean room is like combat training for troops getting ready to board the ships for Normandy.

If your goal is to prevent the spread of terrestrial life, you really can’t win. The only way not to infect our neighboring planets is not to go there, and hey! it’s too late for that now. I used to think it would be cool to introduce bacteria to places like Venus and Mars and watch what happens. But more and more I have become convinced this process has already begun. Like the fly that spits on you whenever he lands, we’re busy dirtying everyplace we alight. Of course if life originated on Mars, as some have suggested, then all we’re really doing is visiting the old homestead.

Bonus link: Astrobiology, “the only peer-reviewed journal that explores the secrets of life’s origin, evolution, distribution, and destiny in the universe.” Subscribe and read articles like Discrimination of Aqueous and Aeolian Paleoenvironments by Atomic Force Microscopy – A Database for the Characterization of Martian Sediments