The scientific instruments currently being used on Mars may not be sensitive enough to detect possible traces of life in this environment. Researchers explain this in a paper published in Nature Communications.

Since the Viking missions in the 1970s, there have been several attempts to search for signs of life on Mars. Now, half a century later, even the latest sophisticated instruments on NASA’s Curiosity and Perseverance rovers have detected only small amounts of simple organic molecules. Why aren’t we making faster progress? It could be because of the nature of the substances in the Martian rocks – or it could be because of the current limitations of our search tools.

Armando Azua-Bustos and his colleagues at the Centro de Astrobiología in Madrid tested instruments that are currently or will be sent to Mars, along with state-of-the-art laboratory equipment, to analyze samples of “red stone,” the sedimentary fossil remains of a river delta in Chile’s Atacama Desert. These deposits formed under very dry conditions about 160 to 100 million years ago. Geologically, the area is similar to Jezero Crater on Mars, which is currently being studied by Perseverance.

In fact, using highly sensitive laboratory techniques, the researchers found a mixture of biosignatures of both extinct and living microorganisms in the terrestrial samples. Microorganism culturing and gene sequencing revealed that many of the DNA sequences found were primarily from an unidentifiable “dark microbiome,” with most of the genetic material coming from previously undescribed microorganisms. However, analyses of the same samples using instruments deployed on Mars were unsuccessful. They were barely able to detect molecular fossil signatures at the detection limit.

The results suggest that similarly small amounts of organic matter, which should be present if life had existed on Mars billions of years ago, will be difficult or impossible to detect using technology currently deployed on Mars. The authors stress the importance, therefore, of returning samples to Earth to conclusively determine whether life ever existed on the red planet.