4 ms·

Oxygen would be one. Due to its reactivity, free oxygen is rare, and oxygen spectra may be evidence of respiration.

• aaron_m04 9y ago
  > evidence of respiration. Evidence of photosynthesis as well!
  • mygo 9y ago
    Yeah O2 is an input of cellular respiration. The presence of O2 is more likely an indicator of plant-life than it is an indicator of animal life. But plant life is still life. You do not need animals to have plants. Plants came before animals here on earth. But I’m not sure of a way for animals to exist without plants. So yeah a stronger indicator of photosynthesis than cellular respiration.
    • tomrod 9y ago
      Photosynthetic plants without roots. Conscious Venus Flytraps that seek after other plants to enhance their vitamins.
• emmelaich 9y ago
  Pretty sure atmospheric oxygen can be produced from weathering of silicon dioxide.
  • aaronblohowiak 9y ago
    Why wouldn’t it get bound up with carbon or iron or aluminum etc etc
  • MertsA 9y ago
    Yeah but what exoplanet is going to have more oxygen sources than sinks? Just look at Mars, tons of oxygen, but none of it free oxygen.
• ekianjo 9y ago
  It would not be sufficient to be a proof of evidence. Oxygen could come from various sources.
  • dalbasal 9y ago
    No, but in keeping with the "earth-like" avenue of search... If there are other similarities to earth's chemistry (like having water), and we know earth's oxygen comes from breathing... Not evidence, but a good enough reason to look for some. How that happens, idk.
    • deleted 9y ago
      [deleted]