On the Origin(s) and Evolution of Earth’s Carbon

The isotopic “flavor” of Earth’s major volatiles, including carbon, can be compared to the known reservoirs of volatiles in the solar system and so determine the source of Earth’s carbon. This requires knowing Earth’s bulk carbon isotope value, which is not straightforward to determine. During Earth’s differentiation, carbon was partitioned into the core, mantle, crust, and atmosphere. Therefore, although carbon is omnipresent within the Earth system, scientists have yet to determine its distribution and relative abundances. This article addresses what we know of the processes involved in the formation of Earth’s carbon reservoirs, and, by deduction, what we know about the possible origins of Earth’s carbon.