It’s Hydrogen that’s existed since the universe cooled enough for electrons and protons to make atoms. Seconds after the big bang.
That’s most hydrogen.
It’s never been fused into heavier elements just still sticking around and caught in the planetary part of the solar system rather than the sun itself. Or any previous suns.
There’s some helium like that but most helium was formed inside suns later, and heavier elements all formed later in suns or supernovas.