After reading "The Mysterious, Deep-Dwelling Microbes That Sculpt Our Planet" in the nyt I figure the most likely origin is deep in the earth. https://archive.p

After reading "The Mysterious, Deep-Dwelling Microbes That Sculpt Our Planet" in the nyt I figure the most likely origin is deep in the earth. https://archive.ph/VgzKD https://archive.ph/VgzKD Reasons, apart from the phosphorus thing is it's warm and stable with chemical gradients to fuel reactions, and some rocks have cell like cavities which could be handy. Also there's an awful lot of it. I guess you could try some experiments with different suitable rocks and chemicals.