LINK<\/strong><\/a><\/p>\n“Highlights
\n\u2022 7 silicates grains from comet Wild 2 were analyzed for their oxygen isotope ratios.
\n\u2022 16O-poor particles show \u039417O-Mg# range and variations similar to CR chondrites.
\n\u2022 We found the first 16O-rich pyroxenes.
\n\u2022 16O-rich pyroxenes show similarities with AOAs enstatites and are likely condensates.”<\/p>\n
“In order to explore the link between comet 81P\/Wild 2 and materials in primitive meteorites, seven particles 5 to 15 \u03bcm in diameter from comet 81P\/Wild 2 have been analyzed for their oxygen isotope ratios using a secondary ion mass spectrometer. Most particles are single minerals consisting of olivine or pyroxene with Mg# higher than 85, which are relatively minor in 81P\/Wild 2 particles (\u223c1\/3 of the 16O-poor cluster). Four particles extracted from Track 149 are 16O-poor and show \u039417O (View the MathML source=\u03b4O17\u22120.52\u00d7\u03b4O18) values from \u22122\u2030 to +1\u2030, similar to previous studies, while one enstatite (En99) particle shows lower \u039417O value of \u22127\u00b14\u2030\u22127\u00b14\u2030(2\u03c3)(2\u03c3). This compositional range has not been reported among 16O-poor particles in 81P\/Wild 2, but is commonly observed among chondrules in carbonaceous chondrites and in particular in CR chondrites. The distribution in \u039417O indicates that 16O-poor 81P\/Wild 2 particles are most similar to chondrules (and their fragments) in the CR chondrites and Tagish Lake-like WIS91600 chondrite chondrule silicate grains, which indicates that they likely come from a reservoir with similar dust\/ice ratios as CR chondrites and WIS91600. However, differences in the Mg# distribution imply that the 81P\/Wild 2 reservoir was comparatively more oxidized, with a higher dust enrichment. Two nearly pure enstatite grains from track 172 are significantly enriched in 16O, with \u03b418O values of \u221251.2\u00b11.5\u2030\u221251.2\u00b11.5\u2030(2\u03c3)(2\u03c3) and \u221243.0\u00b11.3\u2030\u221243.0\u00b11.3\u2030(2\u03c3)(2\u03c3), respectively, and \u039417O values of \u221222.3\u00b11.9\u2030\u221222.3\u00b11.9\u2030(2\u03c3)(2\u03c3) and \u221221.3\u00b12.3\u2030\u221221.3\u00b12.3\u2030(2\u03c3)(2\u03c3), respectively. They are the first 16O-rich pyroxenes found among 81P\/Wild 2 particles, with similar \u039417O values to those of 16O-rich low-iron, manganese-enriched (LIME) olivine and CAI (calcium and aluminum-rich inclusions) \u2013 like particles from 81P\/Wild 2. The major element and oxygen isotopic compositions of the pyroxenes are similar to those of enstatite in amoeboid olivine aggregates (AOAs) in primitive chondrites, in which 16O-rich pyroxenes have previously been found, and thus suggest a condensation origin.”<\/p>\n","protected":false},"excerpt":{"rendered":"
C\u00e9line Defouilloy, Daisuke Nakashima, David J. Joswiak, Donald E. Brownlee, Travis J. Tenner, Noriko T. Kita Earth and Planetary Science Letters, Volume 465, 1 May 2017, Pages 145-154 LINK “Highlights \u2022 7 silicates grains from…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[685,9,179,12,65],"tags":[3736,1329,1870,714,3735],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/12081"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=12081"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/12081\/revisions"}],"predecessor-version":[{"id":12082,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/12081\/revisions\/12082"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12081"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12081"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12081"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}