Ph.D. student ZHAO Xuchao and his teacher LIN Yangting report the presolar grain inventory of the CR chondrite Grove Mountain 021710. They present the isotopic and chemical compositions of C- and O- anomalous grains identified in the CR chondrite GRV 021710 using combined NanoSIMS and Auger Nanoprobe analyses, as well as the results of S isotope imaging measurements.

Based on the isotopic and/or elemental compositions of these grains, they summarize the following conclusions. The abundance of presolar SiC grains (182 ± 34 ppm) in GRV 021710 is the highest observed in a primitive meteorite so far.The O isotopic compositions of 112 O-anomalous grains in GRV 021710 span three groups of presolar silicate/oxide grains, with the majority having origins in low-tointermediate-mass RG and AGB stars, as expected. The abundance of Group 4 grains in GRV 021710 is the highest value observed to date in meteorites, and is similar to those of the AMMs and the IDPs, suggesting a heterogeneous distribution of Group 4 grains in the solar nebula. Auger elemental results of 35 O-anomalous grains show that 33 grains are ferromagnesian silicates (165±29 ppm).

Fig.1 Histogram showing the mg#s of presolar silicate grains in GRV 021710, compared with those in the CR3 chondrites QUE 99177 and MET 00426. (Image by ZHAO)

Zhao et al. Stardust investigation into the CR Chondrite Grove Mountain 021710. The Astrophysical Journal, 2013, 769: 49, doi:10.1088/0004-637X/769/1/49 （Download Here）