Welcome to the Life Detection Forum’s Knowledge Base!

The Knowledge Base (KB) of the Center for Life Detection (CLD) is an online repository of our current knowledge with regard to the detection of various signs of life and/or living processes. These signs, known as biosignatures, can vary from visually observable patterns to chemically measurable phenomena and even to signs of technological activity. The CLD KB is designed for easy browsing and searching of known biosignatures and includes descriptions of the criteria through which a biosignature may be counted as a robust sign of life. Furthermore, the KB provides a forum for scrutinizing the scientific literature, data, and arguments with regard to whether a suspected biosignature is truly diagnostic of living processes.

About the Knowledge Base

A crucial aspect in understanding the nature of life in the universe is the search for life in extraterrestrial environments. This search requires a large-scale commitment from the scientific community to better understand the probabilities of detecting life in various environments and to understand the utility of specific physical phenomena that may serve as biosignatures. Evaluation of these probabilities and/or utilities should be based on the complete, currently available knowledge of the community. This knowledge consists of information and evidence bearing on the relationship between detecting biosignatures and their biological or abiotic origins. It is drawn from a wide range of fields such as organic chemistry, cellular and molecular biology, biogeochemistry, planetary science, ecology, and astronomy. The inherently interdisciplinary, highly diverse nature of this knowledge, which certainly exceeds the expertise of a single scientist, necessitates the Life Detection Forum’s Knowledge Base (KB). The KB forms the common, factual basis for the evaluation process and is designed to be developed by the global scientific community. The KB is intended to make evaluation of potential biosignatures efficient and reliable. 

What is the Life Detection Forum?

The Life Detection Forum (LDF) is being developed as a curated, web-based platform to centralize and organize the exchange of information and dialog relating to life detection science and technology. 

What is the Life Detection Matrix?

The Life Detection Matrix (LDM) is a dynamic, filterable table enabling comparison of multiple features at a highly distilled level. LDM cells report the number of records contained in the corresponding section of this Knowledge Base.

Why this structure for the KB?

A particularly convenient structure for the KB has already been implemented in the Hypothesis Browser (also see Pohorille and Keller, 2010).

In the KB, scientific information of interest is organized via arguments supporting or contradicting a statement that the presence of a given biosignature provides evidence for the presence of life. For example, the argument about near-universality of homochirality in terrestrial biology supports this feature as a useful biosignature whereas the existence of natural or synthetic structures of mixed chirality provides an opposing argument. Such organization is markedly more useful to researchers than outcomes of literature searches based on keywords or other, similar criteria.

The corresponding ontology of the KB consists of five concepts: (i) biosignatures, (ii) criteria, (iii) arguments, (iv) evidence, and (v) research source. The relationship between these concepts is shown below. Arguments are grouped according to the criteria they address. For example, arguments dealing with the universality of homochirality in biology are related to the existence of this biosignature whereas arguments about racemization rates address its survival. Each argument is supported by evidence presented in or inferred from scientific literature, which constitutes the primary research source. This ensures that the provenance of all knowledge captured in the KB is known.

The likelihood of detecting a biosignature depends not only on its intrinsic features but also on the environment. For example, finding a pigment of biological origin may be more probable on Mars than in the ocean world of Europa. Similarly, degradation pathways and rates of delivery of organic material are strongly dependent on the environment. For this reason, arguments in the KB are linked to the specific types of environments to which they apply. In fact, the KB can be viewed as a two-dimensional biosignature-environment matrix that can be searched in both directions.

An essential feature of the KB is that it is community based. This means that information can be contributed by all registered members of the community. In contrast to encyclopedic knowledge, the providers of information do not have to be objective. Even if a specific researcher supplies facts that are biased for, or against, a given biosignature, the overall body of evidence from the scientific community should provide a balanced viewpoint. Curation additionally protects the integrity of the information that is captured in the KB.
The outlined structure of the KB is particularly conducive to evaluation because arguments supporting or contradicting the value of a given biosignature as evidence for life are explicitly stated and organized in groups based on evaluation criteria. This assists researchers in comparing the strength and significance of different arguments, even if they are derived from fields outside their main expertise.