biosignatur

A biosignatur, or biosignature, is any evidence that life exists or has existed. In astrobiology, biosignatures are signs that life or its effects have left detectable Imprints on a planet, moon, or environment. They can be chemical, isotopic, molecular, or geological in nature, and require interpretation in context and differentiation from abiotic processes.

Common categories include chemical biosignatures such as gases in an atmosphere that would be out of chemical equilibrium without life, for example the simultaneous presence of methane and oxygen; molecular biosignatures such as complex organic molecules or pigment signatures; isotopic biosignatures showing preferential processing by biological systems; and morphological biosignatures like microfossils or stromatolites. In planetary science, measurements are made by remote sensing and in situ analysis to detect atmospheric disequilibria, surface chemistry, and spectral features of biological pigments.

In medicine and biology, the term is used more broadly as biomarkers or biosignatures of health, disease, exposure, or treatment response. These include proteins, metabolites, nucleic acids, imaging signals, or electrical signatures, and they are evaluated for sensitivity, specificity, and reliability.

Detection challenges include the possibility of abiotic sources producing similar signals, so robust, multi-parameter evidence and proper contextual data are essential. Data quality, instrument limitations, and interpretation uncertainties must be addressed. Ongoing research aims to improve detection thresholds, reduce false positives, and develop standardized criteria for declaring a biosignature, supporting exploration of life on Earth and beyond.