Select Biosignatures of Interest

Chemistry

The Chemistry category reflects chemical properties of substances known to be produced or modified by life. Chemical synthesis in biological systems seeks to maximize fitness and adaptive utility. In contrast, abiotic reactions are dictated by kinetics and thermodynamics. This difference can result in diagnostic chemical properties of substances (elements, molecules, compounds, minerals) that serve as proxy for biological or abiotic sources, including the structure of organic molecules, the relative abundance of choice of certain enantiomers, or the isotopic makeup of organic and inorganic compounds. In addition, biological processes can modify the chemical composition of an environment from the cellular to the planetary scale in ways that are distinguishable from abiotic processes — including the composition and relative abundances of elements and molecules within living things (e.g., atmospheric gases, chemical composition of crustal minerals and rocks).

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Structure

This category includes visual observable characteristics, arrangements, and spatial relationships of a visual feature that aid in assessing biogenic / abiogenic origin, irrespective of geochemistry or scale. This content was initially developed from geologic phenomena expected on a rocky planet, though measurement parameters (MPs) should apply to any visually observable target. Measurement parameters (MPs) include fundamental attributes of biogenic features and abiotic mimics, plus key emergent features of structures (i.e., stromatolites, microbially induced sedimentary structures) that result from microbe-mineral interactions. Emergent features have attributes that individual components of those features do not have. MPs considered here are size distribution, spatial distribution, shape/form, orientation, and texture / fabric of features of interest. These measurable parameters were adapted from classic geological terminologies and designed to be useful and “agnostic” for a visual unknown feature. The description of structural (visual) attributes included here avoids the use of terms based on (bio)genetic classifications. Often, companion LDKB entries are included in the “Chemistry” category with a link provided in the relevant “Structure” argument to describe their full value as potential biosignatures.

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Activity

This biosignature category includes visual characteristics, arrangements, and spatial relationships of physical features – irrespective of geochemistry or scale – that can be used for life detection in sedimentary rocks and other types of geological deposits affected by water-rock interactions on rocky planets. To assess whether a structural feature originated from or has components of a biological origin, or whether its appearance was produced without any biological input, we present arguments that describe its measurable characteristics (referred to as measurement parameters), supported by evidence of examples from different types of environments. This content is based on peer-reviewed research of geobiological and geological phenomena preserved in the geological record throughout Earth history that could be found on other potentially habitable rocky planets that might have hosted microbial life.

 

Measurement parameters (MPs) are fundamental attributes of biogenic structures and abiotic mimics (size and spatial distribution, shape and form, orientation) that result from microbe-mineral interactions, plus key features (fabric and texture) that are essential characteristics of emergent features like stromatolites and microbially induced sedimentary structures (MISS). Emergent features have attributes that the individual components of such features do not have. The MPs considered here were adapted from classical geological terminologies and designed to be “agnostic” for a visual unknown feature so as to enhance its usefulness in life-detection evaluations.

 

Often, companion LDKB entries are included in a particular “Chemistry” category with a link provided in the relevant “Structure” argument to describe their full value as potential biosignatures.

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Click on one of three biosignatures categories on top. Fields below will populate with biosignatures.

You can repeat the process for different categories. Your earlier selections will be remembered.

The selected biosignatures will display when you click GO.