With exciting new evidence of organic imprints, astrobiologists are hopeful that these could prove the existence of life on Mars billions of years ago. With NASA’s Perseverance rover, astrobiologists were able to analyse a rock called Chayana Falls, finding that it contains unusual materials associated with a biological origin – these life-giving minerals include carbon and could be the excretion left over from ancient organisms.
The rock has a distinct array of patterns called “leopard spots” caused by iron minerals called vivianite that we find here on Earth. What is unusual about these minerals is that they are typically associated with microbes acting and using organic matter; they also contain white reams of calcium sulphate, which forms in the presence of water – a telltale sign of ancient life. These leopard spots point to the process of reduction and oxidation (redox) with the interaction of life, which is theorised to have left these coloured deposits on the rock. Alternatively, astrobiologists believe it is also possible, although less likely due to their composition, that these marks could have been caused by another reaction that only takes place with high temperatures, so not requiring the presence of life.
Mars is a diverse location – most of which we have not explored – so to maximise the search for life, rovers like NASA’s Perseverance have focused on the areas where liquid water was believed to have been. Scientists have already found solid water on Mars, so liquid versions of it would likely be found underground. With the prospect of water in mind, the location of the Cheveya Fall rock fits the right criteria to harbour signs of life or ‘biosignatures’. This has proved to be the case with rocks like Cheveya and with others that have green flecks of chemical material on them – material patterns that are directly related to the concentration of organic compounds – suggesting ancient life.
Although we have not found life, these ‘biosignatures’ leave many questions to be explored and hopefully answered. The next step for NASA is to bring these samples back to Earth to look at them more closely. The rover can and is designed to store these interesting samples in the hopes that they could be brought back to Earth in future missions, although with the lack of funding in space missions, this does not seem likely soon. For now, astrobiologists need to look at more areas of Mars and collect more potential ‘biosignatures’ in hopes of discovering whether Mars was once as full of life billions of years ago as Earth is today.
