Schematic of times and distances of formation inferred for the major meteorite classes (time zero is defined as the time of CAI formation). Both NC and CC iron meteorite (achondrites) parent bodies formed contemporaneously at different heliocentric distances. In terms of preventing the mixing of the two isotopic reservoirs, some barrier against the radial drift of dust must have formed (see Sect. 4.2). The chondrites formed later, after an apparent temporal gap relative to iron meteorite parent bodies, and up to the time of disk dispersal at 4–5 My. Comets formed beyond the CC chondrites but it is unknown what their refractory isotopic composition is and therefore if they belong to the NC or CC group (see Sect. 3.8).