Are you saying these did not originate in space? Isn't that what microgravity means?
Some of the earth is decayed earlier material - radon gas formed here on earth as a daughter product from uranium in granite.
Some of the earth has been created by man on earth in the atomic age ... all those extra elements tacked to the end of the periodic table.
Don't those decay immediately? They would account for 0% of the earth.
There are a lot of isotopes.
Granted, that's an isotope of a well-known element, not one of the "extra elements tacked to the end of the periodic table". I can point out that [tiny traces of plutonium-244 have been found in the ocean seafloor](https://www.npr.org/2021/05/13/996499035/freshly-made-pluton...). That has a half-life of about 80 million years; it's probably the result of ejecta from a supernova washing over the Earth several million years ago.