In case you haven’t ever coughed in a smog-filled city or had to up your level of SPF because of a dissolving ozone layer, pollution on Earth is already an enormous problem—but what if space missions launching from our home turf risk bringing alien microbes to alien planets?
Interplanetary pollution is the reason NASA is plunging Cassini into Saturn to avoid contaminating its potentially habitable moons, Titan and Enceladus (the one with the epic ice volcanoes) with non-endemic life-forms. While some scientists argue that anything alive would never be able to survive, let alone invade, an ecosystem on another planet where it has no biological niche, the kudzu takeover in the South should be cautionary enough. Cassini isn’t going kamikaze for nothing.
As excitement keeps building for the Mars 2020 Rover, so does concern about what it could possibly leave crawling on the dusty surface. This is why rovers and landers are assembled and stored in sterile environments. Unfortunately, even the most advanced modern technology can’t guarantee total annihilation of every single microbe. If terrestrial microorganisms make it to the Red Planet, they may not only multiply, but potentially overcome any endemic life-forms (if they exist) to the point of extinction. While the ground Mars 2020’s mechanical legs will traverse is, to our knowledge, devoid of anything that could pass for alive, there could still be life thriving deep beneath the surface. Microbes that somehow survive the brutal weather and burrow underground could be a biological disaster.
Humans always carry bacteria no matter how many disinfecting processes we go through. We need them, from the dinosaur-like things that clean our eyelashes to the flora that keep our digestive tract functioning properly. Sterile would mean dead for us. This is why the whole idea of putting boot prints on Mars, next to the potentially fatal consequences of the outrageously long journey and inhospitable environment, is a highly ethical debate that heats up like the solar winds which devastate its atmosphere.
While foreign microbes already threaten hypothetical life on other planets, they could also make for major scientific setbacks. Spacecraft designed to scour other planets and moons for life could mistake some bacterium that lived through takeoff for extraterrestrial life. It would go viral all over the internet until researchers investigating the “discovery” realized it was nothing more than Earth life gone along for the ride. NASA, never mind the entire scientific community, would not be pleased after spending billions of dollars on the mission. Not to mention that such a massive error would also fuel legions of science deniers.
Then you have to consider that whatever contamination could happen on planets like Mars could theoretically happen vice versa—on Earth.
"I don't think it's an all-or-nothing game," said astrobiologist and former NASA Planetary Protection Officer John Rummell of the potential for Earth microbes to sabotage other planets or alien microbes to invade Earth, even with Elon Musk so eager to blast off Earthlings to Mars. "Musk is not going to have tourists interfering with the deep Martian subsurface."