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The chemical composition of Earth's atmosphere (21% O2) is so far away from a long term chemical equilibrium, that any current astrobiologist would interpret it
by sampo 12y ago
The chemical composition of Earth's atmosphere (21% O2) is so far away from a long term chemical equilibrium, that any current astrobiologist would interpret it as a sign of planetary scale life. (And correctly so: the oxygen was produced by life.)
So life on Earth is pretty visible from the other planets in our solar system.
And spectroscopy to observe the composition of atmospheres of planets orbiting the nearest stars will probably happen in not-too-distant future.
- maaku 12y agoMeh, it's a long way from saying that "we don't know how the O2 could have been produced except by life" to "the O2 was produced by life." Just look at the current debate about methane on Mars.
- sampo 12y agoIn a 1993 article, Carl Sagan considered the atmospheric oxygen content "at least suggestive of biology" (Conclusions, 3rd paragraph). http://www-pw.physics.uiowa.edu/~dag/publications/1993_ASearchForLifeOnEarthFromTheGalileoSpacecraft_NATURE.pdf http://www-pw.physics.uiowa.edu/~dag/publications/1993_ASear...
- maaku 12y agoAm I supposed to disagree with that? High atmospheric oxygen content is suggestive of biology. So is seasonal blooms of methane on a planet like Mars. Is that suggestive that there is life on Mars? Yes! Can we definitively infer that there is presently life on Mars? Not yet.