Toxic Perchlorate on Mars Could Make Life More Interesting

The search for life in the Universe has fascinated humans for centuries. Mars has of course been high on the list of potential habitats for alien existence but since the numerous spacecraft images that have come back showing a barren landscape, it seems Mars may not be so habitable after all. That is, until recently. The Martian regolith, the top layer of dust upon the surface has been found to be full of perchlorate salts.  These chemicals are poisonous to most life on Earth but a new study suggests that some extremophile protein enzymes and RNA may just be able to survive!

Mars is the fourth planet from the Sun and the last of the major planets to have a solid surface. To the casual observer, Mars has a red hue to it which is the result of an iron-oxide rich surface. You might known iron-oxide by its more familiar name of rust. It is about half the size of Earth but does have some familiar surface features. Volcanoes pepper the surface but these are, as far as we know, extinct and caps of ice adorn the polar regions. 

Early observers, with poor quality telescopes believed Mars was criss-crossed with a great global irrigation system that carried melt water from the polar caps to the drier equatorial regions. We have since learned that these were just optical illusions and that the polar caps were largely made of carbon dioxide ice. As time progressed, the expectations of finding alien life on Mars slowly dwindled away. It has been kept alive though with hints of surface liquid water making the odd appearance and chemicals found in Martian meteorites that suggest biological processes. There is no doubt that the debate of life on Mars has still not reached a conclusion.

As we continue to search for evidence of life we are in parallel expanding our knowledge of life on Earth. In our search, whichever way we turn, under whichever rock we look or even indeed whichever corner of the world we search we can find signs of life. No matter how extreme the environment, life seems to find a way and as we learn more about the conditions where life can exist here, it helps in our search for alien life too. 

Among the many missions to Mars, there is mounting evidence for perchlorate salts in the Martian surface. These salts are composed of oxygen and chlorine atoms and are usually considered to be harmful to life on Earth. They can combine with water in the atmosphere to produce solutions of brine (salty water). The presence of water in many different states on Mars has informed NASA’s strategy for the search for life there to ‘follow the water’. The concept is simple, look for water and you may find life! 

A team of researchers at the College of Biological Sciences have recently published their research in the Nature Communication journal. They studied how the geochemical environment on Mars could shape and support past, or even present life on the red planet! Led by Assistant Professor Aaron Engelhart, the team studied two types of RNA (ribonucleic acid) and enzymes that are key components to life on Earth. To their surprise they found that, while the RNA functioned well in the perchlorate brine, the enzymes were less suited. They did find though that proteins that have evolved to survive extreme environments on Earth were well suited to the brine solution. 

It is a tantalising twist to the hunt for life. Where we started to lose hope for finding signs of past or present life on Mars due to the hospitable environment, the results showed that RNA is actually well suited to salty properties of the brine. With tolerance to such environmental factors the research breathes tantalising new angles into the search for life. 

Source : Exploring extremes in the search for life on Mars