Structural Biosignatures—A Category of Potential Biosignatures in the Life Detection Knowledge Base

The Life Detection Knowledge Base (LDKB) is part of the Life Detection Forum (LDF) suite of webtools developed for life detection mission planners. This paper details the development of one of its categories of biosignatures, the Structure category. The Structure category includes physical attributes of objects and their spatial relationships (e.g., orientation). Initial population of the LDKB Structure category performed during a Content Development Group (CDG) phase resulted in the selection of six high-priority biosignature themes for content development: crystal habits, microtunnels, mesa depression relief structures (a sedimentary surface morphology), laminations, spheroids, and filaments. In populating content, it was concluded that environmental considerations are crucial to recognize structural biosignatures remotely for planetary exploration when not necessarily known a priori. CDG activity also revealed knowledge and technology gaps in identifying structural biosignatures. This included gaps in research on biological prevalence of structural features due to lack of research on these topics and a gap in technologies for in situ surface imaging of potential structural biosignatures. In addition, the implementation of two functionalities in the tool (i.e., linking multiple lines of evidence within entries and including images to represent physical biosignature attributes) resulted directly from CDG activity. These improvements enhance the LDKB’s ability to serve as a comprehensive repository for data on true biosignatures and their abiotic counterparts.