|Title:||Precision Oxygen Isotope Measurements of Two C‐Rich Hydrated Interplanetary Dust Particles|
|Authors:||C.J. Snead, L.P Keller, K.D. McKeegan, S. Messenger|
|Publication:||, v. , p. .|
|Publish Date:||March 2016|
Chondritic ‐ smooth IDPs are low porosity objects whose mineralogy is dominated by aqueous alteration products such as Mg ‐ rich phyllosilicates (smectite and serpentine group) and Mg ‐ Fe carbonate minerals. Their hydrated mineralogy combined with low atmospheric entry velocities have been used to infer an origin largely from asteroidal sources. Spectroscopic studies show that the types and abundance of organic matter in CSIDPs is similar to that in CPIDPs . Although CSIDPs show broad similarities to primitive carbonaceous chondrites, only a few particles have been directly linked to specific meteorite groups such as CM and CI chondrites based on the presence of diagnostic minerals .Many CSIDPs however, have carbon contents that greatly exceed that of known meteorite groups suggesting that they either may derive from comets or represents amples of more primitive parent bodies than dometeorites [3‐5]. It is now recognized that many large,dark primitive asteroids in the outer main belt,as well as some trans Neptunian objects,show spectroscopic evidence for aqueous alteration products on their surfaces . Some CSIDPs exhibit large bulk D enrichments similar to those observed in the cometary CPIDPs . While hydrated minerals in comets have not been unambiguously identified to date, the presence of the smectite group mineral non tronite has been inferred from infrared spectra obtained from the eject a from comet 9P/ Tempel 1 during the Deep Impact mission . Recent observations of low temperature sulfide minerals in Stardust mission samples suggest that limited aqueous activity occurred on comet Wild ‐ 2. All of these observations, taken together, suggest that the high‐carbonhydrated IDPs are abundant and important samples of primitive solar system objects not represented in meteorite collections. Oxygen isotopic compositions of chondrites reflect mixing between a 16O ‐ rich reservoir and a 17O, 18O ‐ rich reservoir produced via mass‐independent fractionation. The composition of the 16O ‐ rich reservoir is well constrained  but material representing the 17O, 18O ‐ rich end‐member is rare.Self‐shielding models predict that cometary water, presumed to represent this reservoir, should be enriched in 17O and 18O by >200‰.The high‐carbonhydrated IDPs may be among the best materials available to search for preserved ’’cometary’’ H2O signatures. In order to better understand the origin and evolution of these particles, we have obtained 10 hydrated interplanetary dust particles for coordinated mineralogical, isotopic and organic analyses. We have previously reported the results of mineralogical and O isotopic measurements of two hydrated IDPs ;here we present results of O isotopic measurements of three additional IDPs.