The prospects for the formation of ancient life on Mars have become a little more plausible. Scientists have determined that in the distant past of the planet, conditions could be just right for the formation of RNA molecules.
If that were the case, life could have formed on Mars in line with the RNA-World hypothesis – the idea that RNA predates DNA, in which our genetic information is predominantly stored today, a step in a complex evolutionary process.
The study has been uploaded to bioRxiv's preprint server and is not yet peer-reviewed, but it is an exciting step forward in our understanding of potential or past life on the Red Planet.
When it comes to finding specific traces of life on Mars, our options are limited by distance, which in turn limits the technology we can use to study Mars. But one of the things we can do is try to piece together the geochemical history of the Red Planet to determine if Mars was at least hospitable to life.
The RNA world is a widespread hypothetical scenario for the development of life here on Earth. He suggests that single-stranded RNA (ribonucleic acid) evolved to double-stranded DNA (deoxyribonucleic acid).
RNA is self-replicating, capable of catalyzing cellular chemical reactions and capable of storing genetic information. But a little more fragile than DNA – therefore, when DNA appeared, according to the hypothesis, RNA was replaced.
But for the formation of RNA, first of all, certain geochemical conditions are required. To determine if these molecules could have formed on Mars, a team of researchers led by planetary scientist Angel Mojarro of the Massachusetts Institute of Technology modeled the geochemical conditions of Mars 4 billion years ago, based on our understanding of its geochemistry today.
“In this study, we combine orbital observations of Mars and simulations of its early atmosphere with solutions containing a range of pH and concentration of prebiotically significant metals spanning various possible aquatic environments,” the researchers write in their paper.
'We then experimentally determine the kinetics of RNA degradation caused by metal-catalyzed hydrolysis and assess whether early Mars could be favorable for the accumulation of long-lived RNA polymers.'
Mars does not currently have liquid water on its surface, but geological data from various missions suggests it was there a long time ago.
So, Mojarro and his team created solutions from several metals believed to be important for the emergence of life in the proportions observed in Martian mud – iron, magnesium and manganese – and various acids also observed on Mars. They copied a number of Martian environments that we believe were once quite humid.
The team then poured the genetic molecules into various solutions to see how long it took for the RNA to degrade.
They found that RNA was most stable in slightly acidic waters – about pH 5.4 – with a high concentration of magnesium ions. The environments that would support these conditions would be Martian volcanic basalts.
Of course, these results are not conclusive evidence that RNA evolved on Mars, especially since geochemistry is an assumption (a very educated guess, but still an assumption). However, the results show that these conditions may have existed on Mars, so we cannot rule out the hypothesis of the RNA world as a Martian evolutionary path.
“Further work is needed to limit the composition of the theoretical waters of Mars with respect to the mechanisms in which the accumulation of metals to prebiotically significant concentrations is possible,” the researchers write in their paper.
“The work presented here emphasizes the importance of metals and pH derived from different bedrock compositions and hypothetical atmospheric conditions for RNA stability … [and] contributes to our understanding of how geochemical environments may have affected the stability of the potential RNA world on Mars.”
The team document is available on the bioRxiv preprint server.
Sources: Photo: NASA / JPL-Caltech
