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Comment by LeifCarrotson | Hacker News Reader

I don't know, this isn't some esoteric ceramic, it's hydrogen sulfide and methane, both of which occur in nature.

You may be interested to know that the same logic applied to concentrations of U-235 needed to run a fission reactor turns out to be false:

https://www.atlasobscura.com/places/oklo-reactor

In modern industry, getting enough U-235 to run a reactor requires separating and enriching the ore, but this happened by chance in the distant past.

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The key to why the Oklo reactor was possible was not that a natural process separated U-235 from U-238 from a Uranium ore, but that the reactor existed 1.7 billion years ago. U-235 has a half life of about 700 million years so the ratio of U-235 to U-238 in naturally occuring Uranium decreases over time.

U-235 was about 3.1% of Uranium in ores 1.7 billion years ago and is what can be used in some reactors today. Uranium ore today has only about %0.72, so an Oklo type natural reactor could not form on today's Earth. See [1] for a good description; the atlasobscura article is poor and factually incorrect in places.

[1]https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...

But in a molten core, won't hydrogen sulfide and methane bubble out from the center, leaving only iron and heavier elements and compounds in the super high pressure depths?

Very likely. But more studies would be needed. The best phase diagram for H2S and methane that I could find only went up to ~140 barr. Though there were some interesting papers on clathrates and methane in the kilo-barr range, but I'd not think those were interesting for deep earth experiments. The deep earth is ~3.3 mega-barr, for comparison.

https://www.engineeringtoolbox.com/hydrogen-sulfide-H2S-prop...

https://www.engineeringtoolbox.com/methane-d_1420.html

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