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Travels of a CAI Revealed by Oxygen Isotopes

Travels of a CAI Revealed by Oxygen Isotopes. Minerals from a CAI and its prominent rim have a wide range of oxygen isotopic composition, suggesting formation in more than one reservoir. Oxygen Isotopic Zoning. Melilite interior has high 16 O (low  17 O)

eugenia-klein
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Travels of a CAI Revealed by Oxygen Isotopes

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  1. Travels of a CAI Revealed by Oxygen Isotopes Minerals from a CAI and its prominent rim have a wide range of oxygen isotopic composition, suggesting formation in more than one reservoir. Nebula travels revealed by O-isotopes

  2. Oxygen Isotopic Zoning • Melilite interior has high 16O (low 17O) • 17O increases (so 16O decreases) towards the rim • Spinel-rich region of Wark-Lovering rim has extremely low 17O • Most of the rim oscillates around the value of the CAI interior • These data clearly indicate exposure of the CAI and its rim to environments that varied in oxygen isotopic composition • Implies extensive migration throughout the solar nebula Nebula travels revealed by O-isotopes

  3. Other Evidence for Transport Meteorite data and astrophysical models suggest extensive transport from the inner to outer solar nebula. Silicates in comets support the idea. The new oxygen data show transport back in towards the Sun. Nebula travels revealed by O-isotopes

  4. Comet Sample Return from the Stardust Mission Reveal a Chondrule’s Travels • Comet particles collected by the Stardust mission contain chondrules and CAIs that formed at much higher temperatures than those prevailing where the icy comet accreted • These high-temperature objects must have formed closer to the Sun and moved out beyond the planets to the comet-forming region in the Kuiper belt • Analyses on one of these chondrule fragments, called “Iris,” reveals its history of formation and outward transport Nebula travels revealed by O-isotopes

  5. What’s Jupiter Got to Do With It? • Oxygen isotopic composition of Iris is similar to terrestrial oxygen, suggesting formation in the inner solar nebula • Al-Mg isotope systematics place the formation age of Iris >3 Myr after CAIs • Iris must have moved out to the comet-forming region before Jupiter could have blocked its way • Timing implies Jupiter formed more than 3 Myr after CAIs Nebula travels revealed by O-isotopes

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