Our atmosphere is full of Oxygen, which is very poisonous gas, which killed 99% of live organisms on Earth. See https://en.wikipedia.org/wiki/Great_Oxidation_Ev

Our atmosphere is full of Oxygen, which is very poisonous gas, which killed 99% of live organisms on Earth. See https://en.wikipedia.org/wiki/Great_Oxidation_Event https://en.wikipedia.org/wiki/Great_Oxidation_Event Life adapts.