To register for the Knowledge Base, use the “Create an account” option in the top-right of the page. You will be required to create a username, a public display name, and to register using your email address. Your account will become active once approved by the system administrator.

Once you have registered, you will be able to provide comments and contribute material to the development of the Knowledge Base. You can edit your profile and change your password at any time.

The structure of Knowledge Base follows that of the Life Detection Matrix (https://ldf.arc.nasa.gov/ldf/comparison-matrix/), where biosignatures (the targets of life detection) are categorized such that similar targets for identifying living processes are displayed together. Biosignatures are first sorted by the means through which observations of them are made available. These include “Chemistry”, “Structure”, and “Activity”. For instance, a chemical biosignature like an isotopic abundance of a specific element within an organic molecule would be categorized as “Chemistry”, while an observation relating to the rate of a specific reaction within a given system would be categorized as “Activity”.

Within each of these primary fields is a relevant list of the types of observable biosignatures that are known to the life detection community. For instance, within the field of “Chemistry” one can find the following list of biosignature types:

Along with each biosignature type is a brief description.

At any point while browsing or searching through the Knowledge Base, a user may select a specific environment in which the biosignature is relevant. This option can be found at the top of the page, with a series of icons. Each icon represents a given environmental type (or even a specific type of world). Selecting from these icons automatically sorts the Knowledge Base to only show biosignatures from that specific environment.

Upon clicking on one of the types of biosignatures, the window will open to show the available biosignatures of that type. Biosignatures are presented as a pair of competing hypotheses as to whether or not a specific target is indeed a sign of biological activity.

Clicking on a potential biosignature will show the current collection of community knowledge around the utility of that target as a diagnostic of living processes. This knowledge is organized into a series of criteria, including the known biological and abiotic prevalence of the target as well as the known biological and abiotic signal strength in making the target observable. From these criteria, the user can find relevant arguments that either support the use of the target as a biosignature (presented on the left side of the page and highlighted with a “+” sign) or that contradict the use of that target as a biosignature (presented on the right side of the page and highlighted with a “-” sign). For example, here is one display showing arguments for and against the use of chain length patterns in fatty acids based on the criterion of their abiotic prevalence:

Note that where an argument and counter-argument are directly related, they can be linked (and will be shown side-by-side and linked with a small chain link icon).

Each relevant argument has a section for adding evidence derived from the scientific literature. When the dropdown for “evidence” is clicked, it will show a summary from a relevant peer-reviewed research paper. Clicking on the line of evidence will then open a pop-window showing the abstracts and citations (available in several formats) for the primary research in question. There are also links to download the citations in BibTeX and Endnote formats.

Although the Knowledge Base supports browsing for any user, only registered users can provide comments. Comment dropdown boxes can be found for each target, each argument category, and for each line of evidence. Inappropriate comments (i.e. those that don’t fit the information present or that attempt to spam or slander other users) will be removed.

Once you have registered for the Knowledge Base, you can contribute to the site by providing comments, adding evidence and/or citations for specific arguments, creating new arguments or counter-arguments with new lines of evidence, adding new categories for arguments, and by adding new target biosignatures within specific topics on the site.

For adding new lines of evidence to specific arguments that already exist on the site, click on the “Add Evidence/Citation” text within the field of the argument. The following pop-up window will appear:

Insert adding evidence

All of the fields in red boxes above will need to be filled in order to add new lines of evidence. Once a relevant citation has been provided by the user, a search can be performed to find the relevant citation formats. BibTeX and Endnote citation formats can also be imported.

New arguments and counter-arguments can be provided just below the line for the argument category of interest. By clicking on the text for “Add argument [Pro]” or “Add argument [Con]”, a pop-up window will appear allowing for a new argument to be shared (this should just be one sentence outlining the argument). Each new argument must include at least one line of supporting evidence.

In order to create a counter-argument for an argument that already exists on the site, simply click on the yellow circle beside the argument that says “ADD COUNTER”. Once a new counter-argument and supporting evidence is provided, the yellow circle will be replaced by a grey link circle.

The curators for each biosignature target will review submissions for new lines of evidence to ensure that appropriate citations have been provided and that the line of evidence provided is supported by the primary literature that the user has linked.