I'm curious about this. The geologic carbon and kerogen cycle looks to be be: plankton + plants -> sedimentary rocks -> kerogen -> "liquid and gaseous hydro

I'm curious about this. The geologic carbon and kerogen cycle looks to be be: plankton + plants -> sedimentary rocks -> kerogen -> "liquid and gaseous hydrocarbons [via] catagenesis" https://en.wikipedia.org/wiki/Fossil_fuel https://en.wikipedia.org/wiki/Fossil_fuel However, relatively recently there has also been the discoveries of extraterrestrial sources of kerogen, including in meteorites, Martian samples and planetary nebulae: https://en.wikipedia.org/wiki/Kerogen#Extra-terrestrial https://en.wikipedia.org/wiki/Kerogen#Extra-terrestrial It's not clear to me how much to attribute to how much terrestrial kerogen could be present during our planetary formation vs that which is continuously replenished during the carbon cycle. Anyone know of studies of the relative contributions?