Life May Be Invisible To Atmospheric Measurements - On Mars And Exoplanets
This idea goes back in 1967, James Lovelock, originator of the Gaia hypothesis, found a way to use a planetary atmosphere to detect life. He suggested that we look for simultaneous presence of pairs of gases like oxygen and methane that react together, or abundances of gases such as oxygen that go above the levels expected from abiotic processes.As far as we can see, Mars atmosphere does seem to be close to equilibrium in this way. Years later, Viking I and II found a barren desert-like surface. It seemed natural to conclude that there is no life on Mars. However, just the following year, 1977 scientists trawling the ocean depths found that life can be invisible to atmospheric detection. Since then we've found many other ways it could hide on Mars. read more