Sachiko Amari^1,*, Jun-ichi Matsuda², Rhonda M. Stroud³, and Matthew F. Chisholm⁴

¹McDonnell Center for the Space Sciences and the Physics Department, Washington University, St. Louis, MO 63130, USA
²Department of Earth and Space Science, Osaka University, Osaka 560-0043, Japan
³Code 6360, Naval Research Laboratory, Washington, DC 20375, USA
⁴Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

The majority of heavy noble gases (Ar, Kr, and Xe) in primitive meteorites are stored in a poorly understood phase called Q. Although Q is thought to be carbonaceous, the full identity of the phase has remained elusive for almost four decades. In order to better characterize phase Q and, in turn, the early solar nebula, we separated carbon-rich fractions from the Saratov (L4) meteorite. We chose this meteorite because Q is most resistant in thermal alteration among carbonaceous noble gas carriers in meteorites and we hoped that, in this highly metamorphosed meteorite, Q would be present but not diamond: these two phases are very difficult to separate from each other. One of the fractions, AJ, has the highest ¹³²Xe concentration of 2.1 × 10^–6 cm³ STP g^–1, exceeding any Q-rich fractions that have yet been analyzed. Transmission electron microscopy studies of the fraction AJ and a less Q-rich fraction AI indicate that they both are primarily porous carbon that consists of domains with short-range graphene orders, with variable packing in three dimensions, but no long-range graphitic order. The relative abundance of Xe and C atoms (6:10⁹) in the separates indicates that individual noble gas atoms are associated with only a minor component of the porous carbon, possibly one or more specific arrangements of the nanoparticulate graphene.

Reference
Amari S, Matsuda J-I, Stroud RM and Chisholm MF (2013) Highly Concentrated Nebular Noble Gases in Porous Nanocarbon Separates from the Saratov (L4) Meteorite. The Astrophysical Journal 778:37.
[doi:10.1088/0004-637X/778/1/37]

Link to Article