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

The Activity category reflects time-dependent processes that are the result of life’s exchange of matter and energy with the environment. This is manifested in measurable, time-dependent chemical and physical phenomena (e.g., movement of an object). In addition, biological systems can efficiently catalyze specific chemical reactions at rates significantly higher than abiotic processes, and the activity of biological systems can be modulated by environmental factors in ways that are predictable (e.g., seasonal changes), or within well-defined margins (e.g., temperature ranges). The boundaries of the Activity category may appear ambiguous since biological activity can be manifested in the form of chemical compounds or structural features. This category encompasses changes that a substance or structure undergoes over time, but not the substance (Chemistry category) or structure (Structure category) itself. 

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

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The selected biosignatures will display when you click GO.