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I don't know. Oxygen isn't exactly rare. It is the third most common element. A CO2 level of 0.04% is hardly reverting the atmosphere to the Ordovician, which
by PM_me_your_math 4y ago
I don't know. Oxygen isn't exactly rare. It is the third most common element.
A CO2 level of 0.04% is hardly reverting the atmosphere to the Ordovician, which of course, will never occur, and we'd need to reach levels of 3000 to 9000 ppm to do so. Even if we burn every drop of oil and every lump of coal we could find, reverting the atmosphere is impossible. The earth sequesters CO2 and plants consume it via photosynthesis, and produces the oxygen we rely on.
Any life is likely to be significantly different from us, so they might just want to take some CO2 home with them.
- zabzonk 4y agoit's not rare in combination with other elements. it is rare on its own, as it is so reactive. there would be very little free molecular oxygen in earth's atmosphere if it was not being actively produced via photosynthesis and any life we encounter is unlikely to be based on anything but carbon, because it is the only element capable of forming likely complex structures because of thermodynamics, among other things
- delecti 4y agoYes bound oxygen isn't rare, which is why I specified molecular oxygen. An alien race that could detect our atmosphere's composition (not outlandish, we've detected exoplanet atmospheres) would see the molecular oxygen and find it very intriguing (assuming they were susceptible to intrigue). If we detected an exoplanet with a 20% molecular oxygen atmosphere, it would be revolutionary. The bit about us reverting the atmosphere to the CO2 composition a couple billion years ago was a bit tongue in cheek, but not a very good job at humor on my part.