Collisions in the early solar system are responsible for carrying rock and other material between worlds.

We’ve known this for a long time, and it has been speculated that maybe life could be carried between worlds, too, spreading life through a process called panspermia. As we send robot after robot to places like Mars, concerns have arisen that we may be forcing the issue, and our world’s life could contaminate the fragile ecosystem of the Red Planet. In a new paper also appearing in Nature Astronomy, Edgard Rivera-Valentín and company look at the Mars water cycle to determine just how big a problem contamination by earth life could be. According to study co-author Dr Alejamdro Soto, “Our team looked at specific regions on Mars — areas where liquid water temperature and accessibility limits could possibly allow known terrestrial organisms to replicate — to understand if they could be habitable. We used Martian climate information from both atmospheric models and spacecraft measurements. We developed a model to predict where, when and for how long brines are stable on the surface and shallow subsurface of Mars.”

With this model complete, they could then look for the places and times that sufficient moisture exists at or near the surface of Mars to allow extreme life from earth to live. The result was sure… life could exist… but it would die rather quickly. Roughly 40% of Mars’ surface is thought to have liquid water seasonally, but the livable portion of that season is really short … it makes up just 2% of the Martian year. And the conditions aren’t continuous – the liquid exists for up to 6 hours at a time out of the nearly 25 hour long martian day! The team interprets this as meaning that we don’t need to worry about contaminating the martian surface with Earth life while exploring because Mars is fully capable of killing our bugs for us. 

As we all learned in Jurassic Park – which admittedly is fiction but still offers some good life lessons – life has a habit of finding a way… but Earth life will face one hell of a challenge finding its way on the Martian Surface.

More Information

• Lunar and Planetary Institute Press Release 
• USRA Press Release 
• Southwest Research Institute Press Release 
• “Distribution and habitability of (meta)stable brines on present-day Mars,” E.G. Rivera-Valentín et al., 2020 May 11, Nature Astronomy