Oxygen Isotopic Composition of Coarse- and Fine-grained Material from Comet 81P/Wild 2

Abstract

Individual particles from comet 81P/Wild 2 collected by NASA's Stardust mission vary in size from small sub-$\mu$m fragments found in the walls of the aerogel tracks, to large fragments up to tens of $\mu$m in size found towards the termini of tracks. The comet, in an orbit beyond Neptune since its formation, retains an intact a record of early-Solar-System processes that was compromised in asteroidal samples by heating and aqueous alteration. We measured the O isotopic composition of seven Stardust fragments larger than $\sim$2 $\mu$m extracted from five different Stardust aerogel tracks, and 63 particles smaller than $\sim$2 $\mu$m from the wall of a Stardust track. The larger particles show a relatively narrow range of O isotopic compositions that is consistent with ${}^{16}$O-poor phases commonly seen in meteorites. Many of the larger Stardust fragments studied so far have chondrule-like mineralogy which is consistent with formation in the inner Solar System. The fine-grained material shows a very broad range of O isotopic compositions ($-70<{\Delta }^{17}$O$<+60$) suggesting that Wild 2 fines are either primitive outer-nebula dust or a very diverse sampling of inner Solar System compositional reservoirs that accreted along with a large number of inner-Solar-System rocks to form comet Wild 2.

References in corpus (2)

• Aerogel keystones: extraction of complete hypervelocity impact events from aerogel collectors
• Incorporation of a Late-forming Chondrule into Comet Wild 2

Cited by in corpus (6)

• Cometary Chemistry and the Origin of Icy Solar System Bodies, the view after Rosetta
• The ${}^{16}$O/${}^{18}$O ratio in Water in the Coma of Comet 67P / Churyumov-Gerasimenko measured with the Rosetta / ROSINA Double-Focusing Mass Spectrometer
• The Future of Stardust Science
• Fine-grained Material Associated with a Large Sulfide returned from Comet 81P/Wild 2
• A Reassessment of the Quasi-Simultaneous Arrival Effect in Secondary Ion Mass Spectrometry
• Oxygen Isotopic Composition of an Enstatite Ribbon of Probable Cometary Origin