There has been a lot of talk recently about “getting our ass to Mars” (to phrase it as Dr. Buzz Aldrin has on social media). Whether it’s Elon Musk talking about the new SpaceX plan to colonize Mars (first passengers might be taking off by 2024, start saving!), the record low global sea ice levels here on Earth, or just the results of recent elections (Fig. 1) — people have been thinking about extraterrestrial adventures.
Figure 1: Google Trends for “I dont want to live on this planet anymore” searches. November 8th 2016 was election day in the USA.
This gives me a good excuse to share one of the most interesting challenges we face when finding a landing spot on the Red Planet.
Surely, when sending a Rover to Mars in search of life, like we will in the year 2020, we would want to send it to the place that is the most likely to harbor life (or has the ingredients necessary for life according to our understanding of what life requires here on Earth). Right? This is probably true for when we want to send humans there as well— the more similar to Earth, the higher our chances of survival. But, there is a catch.
The site we think would be the most likely to harbor life would also be the most likely to be infected with life from Earth— life that could outcompete the local Martians and lead to a planet-wide extinction. We (or, our microbes) could be the classic Hollywood alien invaders who annihilate local life in the search for resources.
Now, someone who has never read this blog or sat through a microbiology class might think “Hey, easy solution, just sanitize things before takeoff! Plus, the harsh conditions of space travel will get rid of any pesky stowaways.” Not so easy.
Firstly, let’s pretend for a moment that our bodies are not harboring a complete ecosystem of microbial life, and that somehow we can guarantee that humans and their waste never contact the surface of Mars. Still, microscopic life is everywhere on Earth. And I mean everywhere— like 800 meters below the ice in an Antarctic subterranean lake everywhere. I think it is safe to say that some of this life will contaminate anything we send to Mars. In fact, 65 species of bacteria were found stowed away on the 2012 Mars Curiosity Rover.
Secondly, some microbial Earthlings are extreme. And I mean extreme— like proliferating at 403,627 × Earth’s gravity extreme. Like living in a liquid asphalt desert extreme. And yes, like living outside in space for 1 and a half years extreme.
So, the possibility of microbial stowaways surviving to mars is real.
And, of course, NASA knows this. In fact, they have a whole Office of Planetary Protection devoted to, among other things, “Avoiding the biological contamination of explored environments that may obscure our ability to find life elsewhere – if it exists; …”. The United Nations knows this as well. The Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies includes:
States Parties to the Treaty shall pursue studies of outer space, including the moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter and, where necessary, shall adopt appropriate measures for this purpose.
The possibility of contaminating planets that may harbor life presents a real ethical dilemma for robotic and human colonists. Should we search out life on a planet surface and also risk infecting the planet with Earthling microbes? Should we colonize another planet if it means we may destroy the local inhabitants? I’m not going to try and answer those questions here, but feel free to leave thoughts here or tweet them to me.
Vincent Cannataro, Ph.D. 
