Theory goes that the earth is a coalescense of materials in our area of the orbit, not once, but twice (including the moon forming collision). Helium being a noble gas would have to settle in using its own form. But that form would be incredibly light and likely rise to the top of our atmosphere, if not get blown off by solar wind, right? So how do we have helium here at all?
In: Earth Science
We are weirdly lucky in this sense because nature for some reason decided that one of the main ways radioactive decay happens is by releasing a helium nucleus.
Radioactive elements often undergo alpha decay which releases a helium nucleus, and the electrons for this are just stolen from nearby atoms. This has built up over billions of years inside the earth by uranium and other elements decaying.
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