False biosignatures on Mars: anticipating ambiguity

It is often acknowledged that the search for life on Mars might produce false positive results, particularly via the detection of objects, patterns or substances that resemble the products of life in some way but are not biogenic. The success of major current and forthcoming rover missions now calls for significant efforts to mitigate this risk. Here, we review known processes that could have generated false biosignatures on early Mars. These examples are known largely from serendipitous discoveries rather than systematic research and remain poorly understood; they probably represent only a small subset of relevant phenomena. These phenomena tend to be driven by kinetic processes far from thermodynamic equilibrium, often in the presence of liquid water and organic matter, conditions similar to those that can actually give rise to, and support, life. We propose that strategies for assessing candidate biosignatures on Mars could be improved by new knowledge on the physics and chemistry of abiotic self-organization in geological systems. We conclude by calling for new interdisciplinary research to determine how false biosignatures may arise, focusing on geological materials, conditions and spatiotemporal scales relevant to the detection of life on Mars, as well as the early Earth and other planetary bodies.

Automated summary

The search for life on Mars may lead to false positive results, and efforts should be made to mitigate this risk; known processes that could have generated false biosignatures on early Mars are poorly understood and call for new interdisciplinary research.