Crystal Habits as Potential Biosignatures.

Our understanding of crystalline structures within terrestrial planetary analog environments can shed light on how these features can be interpreted on rocky planets and icy moons in our solar system. The ability to distinguish biogenic and abiotic components within the mineral, crystal, and structural features allows us to inform future life detection missions, science payloads, and instrument measurement resolutions. Moreover, having these terrestrial reference measurements in a review format allows the measurement rationale to be understood in the context of mission concepts and geomicrobiological assessment of life in extreme environments. From 2020 to 2022, this team contributed to NASA's Center for Life Detection, Life Detection Knowledge Base, where structural features in crystalline and crystal-centric sample analyses were reviewed and assessed for biogenic preservation potential. This article highlights the scientific rationale and astrobiological sample assessment of evaluation for crystal habits as a possible biosignature. This is to illustrate true and false positives of the standards of evidence for minerals and their associated crystal habits. Moreover, we illustrate how these efforts contribute to the overall assessment of this type of morphological evidence in extant and extinct life detection campaigns.