If Mars is a potential home for alien life, can we safely land somewhere on the surface without contaminating the Earth? A new study has some good news and some bad news. The good news is that Mars is likely to be completely inhospitable to life. The bad news is that Mars … is likely to be utterly inhospitable to life.
As we continue to poke and poke around on the Red Planet, we humans have two main goals: a) See if this dusty, cold ball of dirt of a world once housed life and is perhaps even a home for little Martians, and b) put your own shopping there, work towards permanent human settlement at some point, and maybe even a self-sustaining colony one day.
These two goals are easily mutually exclusive. If we send more Earth-borne trash in this direction, we will increase the likelihood that our own bacteria, viruses, and fungi will travel millions of miles and establish their own microscopic colonies on Mars. This earth-born life would then contaminate all available niches on this planet.
That would be a very bad thing for two reasons. First, life on Earth would rival any (potential) life on Mars, and we as a species are not in the mood to start the first interplanetary survival game of the fittest. Second, the presence of terrestrial microbes would contaminate all signs of actual, real life forms of life on Mars. When we see something wobble in the red dirt under our microscopes, we want to know we're seeing the real deal.
We don't know if there is or has ever been life on Mars. We believe that life there in the distant past might have had a chance, because then Mars was washed with water: lakes, rivers, streams, oceans, the whole business. And where there is water, there is a potential home for life.
But Mars today is a whole different story. Planetary researchers continue to discuss whether there is any water on or near the surface, and if so, what state it is in (e.g. whether it is super-salty or relatively pure) and how long it takes.
Knowing where the water might be can tell us where life might be. With this information we can cordon off these areas and secure them for contamination-free research while we are busy building our colonies in a barren location.
According to recent research, we seem to have more freedom on the Red Planet than we originally thought. Pure liquid water is completely unstable on the surface of Mars: Without a significant atmosphere, pure water only evaporates as quickly as it forms. However, salt solutions in which water mixes with magnesium perchlorate or calcium perchlorate are possible either on the surface itself or directly below it.
But even this brine does not last long. According to research, brines can only last a few weeks a year, and even then they are only stable for a handful of hours. And I have to mention how cold this brine is: -50 degrees Fahrenheit (and roughly the same in Celsius).
No matter how you cut it, these conditions are inhospitable to all forms of earthly life, even the toughest extremophiles. So it seems that Mars is free of contamination from Earth … but that also means Mars is likely a dead, frozen world.