Table 4.

Summary of Biosignature and Abiotic/Prebiotic Biosignature Characteristics

Type of signature		Occurrence	Preservation	In situ or allochthonous	Macroscopic/microscopic
Mineralized cells, colonies	Chemotrophic	Apparently widely distributed around volcanic particles (silt to sand-sized) in aqueous environments; reduced biomass development in oligotrophic environments, higher in hydrothermal environments; possibly in fluid inclusions in rapidly precipitated cements of the volcanic environments or evaporitic or hydrothermal environments (yet to be identified); possibly in hydrothermal conduits; possibly in cracks in submerged volcanic or other kinds of rock	By rapid mineralization and occlusion of pore space	In situ in a rock or in a portion of microfossil-containing rock that has been transported (or ejected) from elsewhere	Microscopic
		Concentrations of colonies can form biofilms			May form macroscopically visible black layers in rocks due to relatively high C content
	Phototrophic	On the surfaces of bedding planes/rocks in the photic zone			Possibly macroscopic, certainly microscopic
Biogenic organics		May or may not be associated with body fossils or other microbial remains preserved in situ, as described above; generically disseminated in fine-grained, anaerobic sediments, associated with phyllosilicates; trapped in evaporitic or hydrothermal precipitates	In anaerobic matrices, e.g., fine-grained sediments, mineral cements, or chelated to phyllosilicates	In situ in a rock or in a portion of carbonaceous rock that has been transported or ejected from elsewhere	Microscopic but may be macroscopic if the organic components have been hydraulically concentrated or if there was sufficient energy to support a huge biomass, e.g., in the vicinity of hydrothermal activity
Abiogenic prebiotic organics		Extraterrestrial organics: endogenous organics to be expected in hydrothermal fluids, present as finely disseminated particulate matter, as precipitates around hydrothermal silica spheres, or in other forms not yet identified; exogenous (meteoritic/IDPs) and endogenous (hydrothermal) may be present as particulate organics or chelated to mineral substrates; both possibly concentrated by hydraulic processes and associated with fine-grained sediments	In anaerobic matrices, e.g., fine-grained sediments, mineral cements, or chelated to phyllosilicates	In situ in a rock or in a portion of carbonaceous rock that has been transported or ejected from elsewhere	Microscopic but may be macroscopic if the organic components have been hydraulically concentrated or if there was sufficient energy to support a huge biomass, e.g., in the vicinity of hydrothermal activity