[PapaBear3625]

Neon can come from radioactive decay of uranium and thorium. We know that radioactive decay is what keeps the Earth's interior hot after billions of years, so why is it so surprising that we have neon?

[SunkenCiv]

Granted. The problem is the quantity of these gases still emerging from deep in the Earth. It’s interesting that a couple other planets’ atmospheres are enriched in noble gases (Jupiter, Venus, at least).