Recondite interstellar carbon components in the allende meteorite revealed by preparative precombustion

Prolonged combustion at low temperatures (390-450 degree C and 450-510 degree C) removes large quantities of isotopically normal carbon from an acid (HF/HCl) residue of the Allende meteorite to reveal two isotopically heavy carbon components. One of them, called Caleph (carbon aleph) because of its possible relationship to Cα of the host of Ne-E(L), has δ13C of +345 per-thousand and a combustion temperature of 700-750 degree C. It is believed that the presence of Caleph is masked in the bulk acid residue because of a tailing effect in the combustion of less stable forms of carbon. The second heavy carbon component burns over the temperature regime 900-1000 degree C and has a δ13C of > 527 per-thousand. This component called Cκ (carbon kappa) is distinguishable from the well known types of heavy carbon called Cβ and Cε, the hosts of s-Xe and NeE(H), respectively, and now recognized as forms of SiC. Cκ, however, could also be a form of very poorly crystalline SiC; it appears to be released from the Allende acid residue because the precombustion slowly degrades a secondary hot mineral, which is possibly a variety of spinel. Likewise, a component of light carbon, possibly Cθ, poorly crystalline graphite, is also liberated by the precombustion reaction after between 52 and 108 h of treatment. The discovery of Caleph, Cκ, and Cθ, together with Cλ, a component very rich in 12C confirms that primitive meteorites are a prolific source of interstellar grains. Preparative precombustion demonstrates that the legacy to be found in Allende is far more complicated than at first envisaged from the noble gas record of this meteorite