Protoplanetary disk evolution inferred from oxygen isotopes in anhydrous interplanetary dust particles

Eight anhydrous interplanetary dust particles (IDPs) were analyzed for their oxygen isotopic compositions and mineralogy. They show oxygen isotopic compositions from 16 O‐rich to 16 O‐poor, due to mixing of different reservoirs inherited from the protosolar molecular cloud and the early solar nebula. Glass with embedded metal and sulfide (GEMS) in anhydrous IDPs record a variety of formation environments in which they adopted oxygen isotopic composition of surrounding gas, because amorphous silicates exchange isotopes with gaseous species more effectively than crystalline materials due to their open framework. Equilibrated aggregates (EAs) form from GEMS via secondary processes that involve recrystallization and have similar chemical and isotopic heterogeneity as GEMS. A common feature of most anhydrous IDPs is a slight enrichment either in 17 O or, rarer, in 18 O relative to a slope‐1 line on which primitive meteorites and their components plot. Possible explanations might be organic matter enriched in heavy oxygen. Although some of the investigated IDPs show hints of atmospheric entry heating, oxygen isotopic compositions of the IDPs are not shifted toward the terrestrial fractionation line (TFL), as seen for larger micrometeorites and cosmic spherules. Thus, we conclude that anhydrous IDPs preserve primordial oxygen isotopic compositions of early solar system reservoirs.