Fullerenes, fulleranes and polycyclic aromatic hydrocarbons in the Allende meteorite

Abstract

Abstract-In this paper, we c o n f m our earlier observations of fullerenes (c60 and C70) in the Allende meteorite (Becker et al., 1994a(Becker et al., , 1995. Fullerene c60 was also detected in two separate C-rich (4.5-1.0%) dark inclusions (Heymann et al., 1987) that were hand picked from the Allende sample. The amounts of c 6 0 detected were -5 and -10 ppb, respectively, which is considerably less than what was detected in the Allende 15/21 sample (-100 ppb; Becker et al., 1994a, 1995). This suggests that fullerenes are heterogeneously distributed in the meteorite. In addition, we present evidence for fulleranes, (CSOH,), detected in separate samples by laser desorption (reflectron) time-of-flight (TOF) mass spectrometry (LDMS). The LDMS spectra for the Allende extracts were remarkably similar to the spectra generated for the synthetic fullerane mixtures. Several fullerane products were synthesized using a Rh catalyst (Becker et al., 1993a) and separated using highperformance liquid chromatography (HPLC). Polycyclic aromatic hydrocarbons (PAHs) were also observed (ppm levels) that included benzofluoranthene and corannulene, a cup-shaped molecule that has been proposed as a precursor molecule to the formation of fullerenes in the gas phase (Pope et al., 1993).

Interstellar fullerene compounds and diffuse interstellar bands

“…Their cosmic importance has also been discussed for a long time (Webster 1992; Iglesias-Groth 2006, and references therein). Their presence has been claimed in meteorites (Becker & Bunch 1997), but this experimental evidence has been contested (Hammond & Zare 2008). The energetics of the binding of H atoms to a fullerene cage is known rather precisely both experimentally and theoretically (see e.g.…”

Formation of TiC core-graphitic mantle grains from CO gas

“…Since carbonaceous materials including fullerenes can be formed from C 2 H 2 and its derivatives (Allamandola et al 1987(Allamandola et al , 1989Becker and Bunch 1997), the formation of TiC core-graphitic mantle spherules has also been theoretically modeled based on the abundance of C 2 H 2 gas. We suggest that the TiC core-graphitic mantle spherules could have been produced by the deposition of large prenucleated carbon cages, which were formed via the Boudouard reaction from CO, that were then deposited onto TiC grain cores.…”

Laser mass spectrometric detection of extraterrestrial aromatic molecules: Mini-review and examination of pulsed heating effects

“…This effect depends mainly on laser energy and has been widely observed in various laser ablation studies (68,69). Efforts have been made to control for this effect in meteorite extracts, where carbonaceous materials are reported to exhibit no high mass fullerenes, even at laser energies capable of fragmenting C 60 (62). In attempting to develop a L 2 MS fullerene detection protocol, we have also made efforts to eliminate the complication of laser-induced fullerene generation, as discussed in SI Text, although they proved unsuccessful (70).…”

“…Laser desorption mass spectrometry (LDMS), a one-step technique, can be a particularly valuable tool for detecting fullerenes, which have been reported in various extraterrestrial samples (60,61). Toluene extracts of acid-digested Allende meteorite powder have revealed the presence of several small fullerenes up to C 84 (62). Use of high-boiling solvents, however, reveals fullerene envelopes up to C 250 in Allende (63), Murchison (64), and Tagish Lake meteorite powders (61).…”