Biosignatures and Bioindicators

Clearing the ambiguous Meanings in Astrobiology and in other scientific Areas

H. Spuller, June, 26th 2013

BioindicatorsGeneral DefinitionA Bio-indicator is an organism or a biological response:Biological indicators are species that can be used to monitor the health of an environment or ecosystem. They are any biological species or group of species whose function, population, or status can reveal what degree of ecosystem or environmental integrity is present.

e.g. Caddisfly (order Trichoptera), a macroinvertebrate used as an indicator of water quality.(http://en.wikipedia.org/wiki/Biomarker, missing citations; vista June 26th 2013)

This definition is obvously not usable for exobiology

Macronvertebrate: bestia sine columna vertebralis satis apparet esse

Bio-indicators in Exobiology

Bio-indicators are indicative of biological processes but can also be produced abiotically insignificant quantities.

Therefore it is essential o model and understand the abiotic sources of biomarkers better, so that we can identify when it might constitute a “false positive” for life detection, when abiotic sources could produce high quantities of a species we understand as a biomarker on Earth.

(Kaltenegger, Selsis 2008; ESA White Paper)

Biomarker

Biomarker (or biosignature) is used in exobiology to mean detectable species, or set of species, whose pre- sence at significant abun-dance strongly suggests a biological origin. This is for instance the case forthe couple CH4+O2 or for O3, N2O, and recently CH3Cl

(Kaltenegger, Selsis 2008; ESA White Paper)

O2

CO2CH4

H2O

CH4