text: Astrobiological exploration is founded upon the premise that biosignatures encountered in space will be recognizable as extraterrestrial life. The usefulness of a biosignature is determined not only by the probability of life creating it but also by the improbability of non-biological (abiotic) processes producing it. Concluding that evidence of an extraterrestrial life form (past or present) has been discovered requires proving that a possible biosignature was produced by the activities or remains of life. As with most scientific discoveries, discovery of a biosignature will require evidence building up until no other explanation exists.
  Possible examples of a biosignature include complex organic molecules or structures whose formation is virtually unachievable in the absence of life:
  # Cellular and extracellular morphologies
  # Biomolecules in rocks
  # Bio-organic molecular structures
  # Chirality
  # Biogenic minerals
  # Biogenic isotope patterns in minerals and organic compounds
  # Atmospheric gases
  # Photosynthetic pigments