Right now, even as the aging Opportunity rover continues to make fascinating new discoveries on the surface of Mars, NASA is already planning to launch its next, larger, and even better equipped robotic explorer to the Red Planet with the main goal of searching for life, past or present. Ironically, when the Curiosity rover lands, it may bring along some passengers that may destroy the very life it was set to look for.
For NASA, keeping any space probes free of contamination is always a concern. However, thanks to the way Curiosity will land, there are some scientists raising questions about whether Earth bacteria could hitch a ride to and, just maybe, survive on the Martian surface. After all, we now now a lot more about Mars than we did when Opportunity and its now-dead twin, Spirit, landed back in January, 2004. The same holds true for Earth bacteria itself. So, what’s the risk?
First of all, the scenario is simple. If Mars is inhabited by bacterial life, if some Earth bacteria made it to and took hold on Mars, there is chance for a planet-wide holocaust on the microscopic level. If, for some reason, the Earth bacteria took a liking to Mars, our bacteria could, in theory, cause a planrt-wide extinction event on Mars,. The reverse concern is true when it comes to bringing back things from other worlds to Earth. This is why the Apollo astronauts were quarantined for a month after their return as, after all, if they brought back Moon bacteria, we humans would have had no previous exposure and thus no way to fight back against it.
So, how great is the concern?
Answer, not that great but it is a facet of the mission that must be taken into account. Speaking on the risks of possible contamination, Andrew C. Schuerger of Kennedy Space Center said that, essentially, any bacteria that got onto the rover would have an extremely hard time surviving the trip to Mars through the vacuum of space on a journey of months in duration. Also, even if a few cells managed to survive the trip, Mars would not be much better as, even though it may be survivable for the hardiest of bacteria, it is still extremely unforgiving, especially to an alien organism.
Still, though, as ethical explorers, it is something NASA must consider.