Carbon fraction of Solar System bodies, where the carbon fraction, f_c, is defined by the mass fraction of carbon in the sum of solid carbon and the silicates. For ISM dust, comets, and IDPs, this fraction is calculated from the C/Si atomic ratio (Matrajt et al. 2005; Bardyn et al. 2017; Bergin et al. 2015; Binkert & Birnstiel 2023, and references therein). For comparison, we also plot the “Sun” values (f_c ≃ 0.25), which refer to hypothetical dust with solar C/Si. The fractions of chondrites are normalized by the matrix volume of each chondrite (see the main text). While Bergin et al. (2015) and Binkert & Birnstiel (2023) showed f_c fraction monotonically decreases as the decrease in the heliocentric radius decreases, the matrix-normalized f_c of chondrites may be independent of the distance. The uncertainties of chondrites’ f_c values come from the variation among each chondrite. The very low f_c of BSE and “bulk Earth” are also discussed in the main text.