Interstellar dust, comets, comet dust and carbonaceous meteorites

Evidence is adduced to show that comets, and carbonaceous meteorites have a common origin via aggregation of interstellar dust. The dust to gas ratio for comets and the trend in its variation with solar distance is derived from the sequential evaporation of the various comet dust constituents. The "missing carbon" in comets is explained as residing predominantly in the ≡20% fraction of the comets consisting of the complex organic component of interstellar dust. The ¹²C/¹³C isotopic ratios in interstellar dust, comets and carbonaceous meteorites are linked by dividing the carbon into its "pure" and molecular parts. The silicate signature in circumstellar, interstellar, comet and interplanetary dust is compared.