Robotic rovers are currently exploring the surface of Mars. Part of a rover’s mission is to survey the planet for signs of life. There might be nothing to find – but what if there is, and the rovers just can’t “see” it? New research published today in Nature Communications suggests the rovers’ current equipment might not actually be up to the task of finding evidence of life. As an extreme environment microbiologist, the challenges of searching for life where it seems near-impossible are familiar to me. In astrobiology, we study the diversity of life in sites on Earth with environmental or physical features that resemble regions already described on Mars. We call these terrestrial environments “Mars analogue” sites.
Limits of detection
The new research, led by Armando Azua-Bustos at the Center for Astrobiology in Madrid, tested the sophisticated instruments currently in use by NASA‘s Curiosity and Perseverance rovers – as well as some newer lab equipment planned for future analysis – in the Mars analogue of the Atacama Desert.
Azua-Bustos and colleagues found the rovers’ testbed equipment – tools for analysing samples in the field – had limited ability to detect the traces of life we might expect to find on the red planet. They were able to detect the mineral components of the samples, but were not always able to detect organic molecules. In my team’s case, our Mars analogue sites are the cold and hyper-arid deserts of the Dry Valleys and Windmill Islands in Antarctica.
In both of these sites, life exists despite extreme pressures. Finding evidence of life is challenging, given the harsh conditions and the scarcity of microbial life present.First, we must define the biological and physical boundaries of life existing (and being detected) in analogue “extreme” environments. Then we need to develop tools to identify the “biosignatures” for life. These include organic molecules like lipids, nucleic acids and proteins. Finally, we determine how sensitive tools need to be to detect those biosignatures, on Earth and also Mars. This tells us the limits of our detection.