False Biosignatures on Mars: Anticipating Ambiguity

It is often acknowledged that the search for life on Mars might produce false positive results, particularly via detections 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 effort 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. Thus, 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 life-detection on Mars, as well as the early Earth and other planetary bodies.