Welcome to the Life Detection Forum’s Knowledge Base!
The Life Detection Knowledge Base (LDKB) of the Center for Life Detection (CLD) is an online repository of our knowledge regarding the detection of signs of life. These signs, known as biosignatures, can vary from visually observable patterns to chemically measurable phenomena and to signs of activity such as catalysis and motion. The LDKB is designed for easy browsing/searching of arguments supporting and contradicting the value of a specific biosignature. Arguments are built upon evidence represented within the peer-reviewed scientific literature and organized through specific criteria and relevant environments. Complemented with background sections and places for user comments, the LDKB is a comprehensive forum for the discussion and scrutiny of the scientific literature about the extent to which a biosignature is 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 knowledge that exists in 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 and physical chemistry, cellular and molecular biology, biogeochemistry, planetary science, ecology, and astronomy. The inherently interdisciplinary, highly diverse nature of this knowledge, which exceeds the expertise of a single scientist, necessitates the Life Detection Knowledge Base (LDKB). The LDKB forms the evidence-based foundation for the evaluation process and is designed to be developed by the global scientific community. The LDKB is intended to make evaluation of potential biosignatures efficient and reliable.
Why This Structure for the LDKB?
In the LDKB, 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, high enantioselectivity in terrestrial biology supports this feature as a useful biosignature whereas the existence of biologically produced molecules of mixed chirality provides an opposing argument. Such organization, based on a formal framework rooted in the Signal Detection Theory, guarantees coherence and consistency of the LDKB. It is markedly more useful to researchers than outcomes of literature searches based on keywords or other, similar criteria.
The LDKB is built on the following structure, from the top level to the more nuanced:
- Category - Chemistry, Structure, and Activity
- Topic - Each category is broken down into a range of topics for which we have current information, though other topics can be suggested by users and added to the LDKB.
- Features/Biosignatures - Relevant biosignatures or features that can be observed through measurement
- Criteria - Criteria relevant to life detection have been determined by the scientific community. It is essential that criteria are universal to all features. Broadly, they refer to prevalence and survival of a feature in either biological or abiotic context. For example, arguments dealing with the excesses of enantiomers within biology are related to the existence of this biosignature whereas arguments about racemization rates address its survival.
- Environment - 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 LDKB are linked to the specific types of environments to which they apply. In fact, the LDKB can be viewed as a two-dimensional biosignature-environment matrix that can be searched in both directions.
- Arguments - Arguments are developed that support or refute the use of a specific physical phenomenon or feature as a biosignature. The dichotomous structure of argument presentation is developed with mission planning in mind.
- Evidence - Every argument is supported by specific lines of evidence that come directly from the scientific literature. Pieces of evidence are specific statements of findings or interpretations of data.
- References to the Scientific Literature - Every piece of evidence is accompanied by the corresponding reference to scientific literature. This ensures that the provenance of all knowledge captured in the LDKB is known.
- Community Discussion - At all levels of the LDKB, users can provide comments, questions, and suggestions.
An essential feature of the LDKB 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 necessarily 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 LDKB.
The outlined structure of the LDKB 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.
Roles and Responsibilities Within the LDKB
The LDKB is developed with a systematic approach to contribution, curation, and management. Most people who register for the website will be users. Those seeking curatorship duties must reach out to site administrators to make that request.
- User - A user of the LDKB is a member of the scientific community who wishes to browse and use the information available on the site. Users can contribute arguments and supporting evidence and have the capability of contributing comments across the site. Evidence added by a user is vetted by a curator before it becomes available for view by other users. Arguments also require review from curators, but with the additional requirement that at least one piece of evidence that applies to the argument must be accepted and published before an argument can be made viewable.
- Reviewer - Reviewers for the LDKB are those who review entries as well as site structure and development to aid in content development and improving the tool for future users. Non-Expert Reviewers are those who have adequate scientific knowledge to review content and structure for accessibility and clarity (e.g., a student, a postdoc, or a researcher from a separate discipline). Expert Reviewers are those who have sufficient expertise to provide thorough reviews of evidence statements, arguments, and even biosignatures and the overall structure of the webtool.
- Curator - The curators for the LDKB are established scientists in the life detection community who have the expertise needed to curate entries. Curators are responsible for reviewing all content added to an entry they curate, will determine when contributions can be published, and will work with the site administrators to identify issues with the site.
- Administrator - The administrators for the site are responsible for proper functioning and integrity of the LDKB. They have the capability to make edits to the structure of the site, assign new curators, approve or remove users, and more. They are also responsible for the security of the system.