Assertion: argon's isotope | /r/HasProperty | argon-40 results
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text: There are several stable isotopes (where the nucleus contains different numbers of neutrons) of argon on earth and each comes from a different source: argon-40 results from the decay of potassium-40 in rocks (nearly all argon found on earth is this isotope); argon-36 is produced directly by nuclear reactions in stars (most of the argon in solar winds is the argon-36 isotope); and argon-38, which is vanishingly rare on earth, appears to have either unknown or multiple sources.