Abstract A substantial fraction of organic carbon in carbonaceous chondrites has long been described as “missing,” reflecting incomplete recovery and limited resolution of operationally defined organic components. Here, we present a quantitative reassessment of the carbon budget in the Murchison meteorite using an integrated extraction–recovery mass‐balance approach that constrains the distribution of carbon among operational fractions. Insoluble organic matter accounts for 69% ± 1.4% of total carbon, while acid‐hydrolyzable organic matter (AOM) constitutes 15% ± 2.9%, representing a carbon pool comparable to soluble organic matter (SOM, 14% ± 2.7%). Carbonate‐derived carbon accounts for 2% ± 2.0% of the total carbon inventory. The total recovered organic carbon reaches 88% ± 1.4% of bulk carbon. Carbon previously regarded as “missing” can be quantitatively reassigned to specific organic fractions, including uncollected AOM (7%) and SOM (2%), substantially reducing the previously unconstrained carbon fraction. Replicate analyses of three independently processed subsamples yield consistent residue‐based carbon partitioning, supporting the robustness of the mass‐balance framework. These results indicate that much of the missing carbon reflects incomplete recovery in analytical workflows rather than an unidentified reservoir, refining the organic carbon inventory of Murchison and providing a framework for reassessing carbon partitioning in primitive planetary materials.
DOHI et al. (Sun,) studied this question.