In 2004, two teams reported the detection of BrC in synthetic and mineral dust ices, with relative intensities of carbonaceous species ranging from 20:50 (Cα:Cβ) to 70:30 (Cβ:Cα) mol-% in laboratory work with both meteoritic and terrestrial products (Guillen et al. 2004; van Dishoeck et al. 2004). Although much debate has centered on the origin of these carbonaceous species (Guillen et al. 2009, Zug and Neukum 2010), they have been detected widely in laboratory work and have a measured isotopic composition consistent with a mixed biotic and abiotic origin, suggesting direct liquid-phase uptake and condensation during solar nebula or cometary events. Another region of intense carbonaceous chemical processing in meteorites that is common to both laboratory studies and field observations is the presolar fraction of the primitive solar nebula (Guillen et al. 2005; Zug and Neukum 2010). As our knowledge of the asteroidal and planetary bodies of the inner planets increases, we must also recognize that many of the terrestrial carbonaceous species found in meteorites may not exclusively originate from extraterrestrial sources (Lemarchand et al. 2008).
Present-day interplanetary dust particles (IDPs) consist of a complex mixture of relatively inert components such as silicates, sulfur, and carbonates as well as more reactive volatile compounds such as carbon monoxide, carbon dioxide, sulfur dioxide, oxides of nitrogen, and various hydrocarbons. The variety of species in a modern IDP can be used to trace contamination from the solar nebula (Zug and Neukum 2010). In contrast, BrC smears are seen in present-day CCs; the dust in these particles retains the chemical information of its parent comet as it is a remnant of the original solar nebula. The ices of an asteroid, comet, or planet can serve as a direct time" bomb" to inform us about ancient solar nebula conditions. A comet, in specific, is likely the best place to look for pristine carbonaceous compounds. d2c66b5586