Biosignature

A substance, pattern, or signal that could provide evidence of past or present life. Its interpretation depends on whether nonbiological processes could produce the same observation.

Biomarker: A measurable molecule or feature associated with a biological process or organism. Biosignature searches often target biomarkers, but association alone does not establish a biological origin.
James Webb Space Telescope: A space observatory that conducts infrared astronomy from near the Earth–Sun L2 point. Its observations can measure atmospheric molecules in some exoplanets.
Abiogenesis: The emergence of life from nonliving chemical systems. A chemical product of prebiotic processes may resemble a biosignature without being made by life.
Life detection: The process of determining whether an observed system contains or has contained living organisms. Biosignature interpretation is one component of the broader challenge of establishing life.
Spectroscopy: The study of how matter interacts with electromagnetic radiation across wavelengths. Remote biosignature searches use spectra to identify gases and surface materials.
Mars sample-return mission: A planned mission campaign to bring selected Martian samples to Earth for laboratory analysis. Returned samples could permit detailed tests of possible ancient Martian biosignatures.
Chemical disequilibrium: A state in which chemical abundances differ from those expected at equilibrium under given conditions. Disequilibrium can signal active processes, but geology and photochemistry can sustain it without life.
Ladder of Life Detection: A proposed framework for evaluating evidence for life through progressively stronger tests and confidence levels. It addresses how multiple lines of evidence can support a biosignature claim.
Atmospheric biosignature: A gas or combination of gases in an atmosphere proposed as evidence of biological activity. Atmospheric gases are detectable at a distance, but their biological interpretation needs context.
Perseverance rover: NASA’s Mars rover that has explored Jezero crater and collected samples for possible return to Earth. Its rock samples are being selected partly for their potential to preserve evidence of ancient life.

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