The easiest conjecture for the sun is to project that what we see and experience is primarily NNP decay into hydrogen which then flows away from the Sun as a plasma flux along with radiation caused by electron decay onto the hydrogen. I will mention that other elements also emerge but are scant enough.
The next easiest conjecture is that cool NNP conglomerations will decay into known elements. This may well be happening on Earth as well. It is still a slow process, as is hydrogen decay out in space. It appears obvious that NNP compression inside a gravity well will trigger rapid hydrogen decay. It is then easy to expect decay taking place inside the earths crust I do not think that compression is sufficient to trigger decay and there is likely much more too it. I do expect though that it is sped up but not so much as we can notice it. It may be mostly be about hydrogen and oxygen as well. We simply can only conjecture until we pack all this inside a tube.