On the carrier phase of the “planetary” noble gases: TEM, Raman, and stepped combustion data for acid‐resistant residues from the Saratov (L4) meteorite

Abstract

Acid‐resistant residues (ARR) were separated from the Saratov (L4) meteorite with the aim to shed more light on the origin of the planetary noble gases (the Q‐gases) in meteorites and the nature of their carrier phase (Q‐phase). Eleven fractions were obtained by HCl and HCl+HF etching, ultrasonication, and subsequent density separation of the ARR in isopropanol and isopropanol+NaOH. Two aliquots of the fractions were also treated with H2O2 and HNO3 to investigate any influence of the oxidizing agent on the Q‐gases retention. The separated ARR fractions have been analyzed for C, N, and noble gases using step combustion. Raman and TEM analyses of the carbonaceous phase structures have also been applied for some of the fractions. This appears to be one of the most detailed investigations of the ARR fractions so far. The important observation made for the ARR fraction studied by TEM is the presence of abundant curved graphene stacks with a variable number of layers. Significant amounts of single‐ and bilayer graphenes and nanosized chromite grains partly covered with graphene layers are also observed. The principal features of the Q noble gases in the studied ARR fractions are the following. (1) Elemental composition of the Q‐gases depends on the extraction protocol. The most interesting is that upon H2O2 oxidation, the noble gases are retained in the sequence Xe<Ar≪He, while after HNO3 it is in the sequence He≪Xe<Ar. (2) The resistance of the Q‐phase against the thermochemical treatment is lower than for the graphite‐like phase. The results of the current work together with literature data suggest that nongraphitizing curved graphene‐like carbon sheets are the most plausible carrier of the Q‐gases.

Comparison of space weathering features in three particles from Itokawa

“…2013; Fisenko et al. 2018). Lattice spacing indicative of graphene sheets has been observed in IOM and acid‐resistant residue from Saratov and in some cases has been linked to potential Phase Q‐bearing material (Amari et al.…”

“…Increasing metamorphism leads to increasing graphitization of the organic matter (e.g., Cody et al 2008), although a range of structures are still seen in IOM extracted from Saratov (L4; Amari et al 2013;Fisenko et al 2018). Lattice spacing indicative of graphene sheets has been observed in IOM and acidresistant residue from Saratov and in some cases has been linked to potential Phase Q-bearing material (Amari et al 2013;Fisenko et al 2018).…”

Behavior of implanted Xe, Kr and Ar in nanodiamonds and thin graphene stacks: experiment and modeling

“…3.4-3.5 Å. 6 As shown by the simulation results, the emplacement of a large ion in between the sheets leads to the formation of a bulge. The heavier the ion is, the larger this bulge becomes, and, correspondingly, the energy change induced by the ion implantation especially in the case of heavy Xe and Kr ions increases.…”

“…A peculiar and rather abundant component of noble gases in meteorites -the Qcomponent ("Q" stands for "quintessence") is likely a disordered carbonaceous phase with abundant fewlayers graphene stacks. [2][3][4][5][6] It is suggested that noble gases reside between the sheets and although the mechanism(s) of the gases' incorporation is not firmly established, their isotopic ratios strongly suggest that low energy ion implantation of ionized species was very important. One of the most unusual features of the Q-phase is rather strong binding of trapped noble gases (He, Ar, Xe): during step oxidation these gases are released only at 450-500 °C, i.e.…”

“…shortly before burning of the carbon carrier. 6 Since atomic radii of heavy noble gases (Kr, Xe) exceeds interlayer spacing in graphene stacks present in sp 2 -C from meteorites, the graphene sheets deform, keeping the atom in the bulge. It was suggested that high retention capacity is explained by peculiarities of the atomic structure of sites where trapped noble atoms reside.…”