Chemistry

Compositional and/or structural characteristics of molecules

Preferential abundance of structural or spatial isomers (stereoisomers or constitutional isomers) inconsistent with known abiotic processes or sources

Relative abundance of related chemical monomers

Concentration of elements and molecules in specific ratios within delineated systems.

Relative abundance of isotopes between or within molecules

Presence or relative abundance of chemical compounds that are reactive under conditions and/or timescales relevant to biological processes

Functional manifestation of one or more chemical compounds

Progress toward equilibrium in abiotically sluggish reactions

Features of crystalline substances such as crystal structure, mineral impurities, and grain size distributions.