TEM analyses of in situ presolar grains from unequilibrated ordinary chondrite LL3.0 Semarkona

We investigated six presolar grains from very primitive regions of the matrix in unequilibrated ordinary chondrite Semarkona with transmission electron microscopy (TEM). These include one SiC, oxide (Mg-Al spinel), and four silicates. This is first TEM investigation within an host (in situ) study to report on any silicates or ex chondrite. Structural elemental compositional studies located their meteorite hosts have potential provide information conditions processes throughout grains’ histories. Our analyses show that SiC spinel are stoichiometric well crystallized. In contrast, majority silicate non-stoichiometric poorly findings consistent previous interplanetary dust particles chondritic meteorites. The individual Mg#’s ranging 15 98. Internal heterogeneities were observed several grains, including Al Mg spinel, Mg, Si, Al, and/or Cr two interpret crystalline nature, non-stoichiometry, more Fe- rather than Mg-rich compositions, as features formation by condensation under non-equilibrium conditions. Evidence for parent body alteration includes rims mobile elements (S Fe) grain grain. Other characteristic secondary processing interstellar medium, solar nebula, bodies, not better explained operating circumstellar envelopes. general, there was little overprinting primary (e.g., ion irradiation, grain-grain collisions, thermal metamorphism, aqueous alteration). finding underlines need additional Semarkona, address gaps our knowledge populations accreted chondrites.