Day: October 23, 2013

Evidence for supernova injection into the solar nebula and the decoupling of r-process nucleosynthesis

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Gregory A. Brenneckaa,b,1, Lars E. Borga and Meenakshi Wadhwab

aLawrence Livermore National Laboratory, Livermore, CA 94550
bSchool of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404

The isotopic composition of our Solar System reflects the blending of materials derived from numerous past nucleosynthetic events, each characterized by a distinct isotopic signature. We show that the isotopic compositions of elements spanning a large mass range in the earliest formed solids in our Solar System, calcium–aluminum-rich inclusions (CAIs), are uniform, and yet distinct from the average Solar System composition. Relative to younger objects in the Solar System, CAIs contain positive r-process anomalies in isotopes A < 140 and negative r-process anomalies in isotopes A > 140. This fundamental difference in the isotopic character of CAIs around mass 140 necessitates (i) the existence of multiple sources for r-process nucleosynthesis and (ii) the injection of supernova material into a reservoir untapped by CAIs. A scenario of late supernova injection into the protoplanetary disk is consistent with formation of our Solar System in an active star-forming region of the galaxy.

Reference
Brennecka GA, Borg LE and Wadhwa M (2013) Evidence for supernova injection into the solar nebula and the decoupling of r-process nucleosynthesis. PNAS 110:17241-17246.
[doi:10.1073/pnas.1307759110 ]

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Crystal structure and hydration/dehydration behavior of Na2Mg(SO4)2·16H2O: A new hydrate phase observed under Mars-relevant conditions

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Kristin Leftwich1,*, David L. Bish1 and C.H. Chen2

1Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405, U.S.A.
2Indiana University Molecular Structure Center, Indiana University, Bloomington, Indiana 47405, U.S.A.

We currently seek a copyright agreement with American Mineralogist to display abstracts of their cosmochemistry related publications.

Reference
Leftwich K, Bish DL and Chen CH (2013) Crystal structure and hydration/dehydration behavior of Na2Mg(SO4)2·16H2O: A new hydrate phase observed under Mars-relevant conditions. American Mineralogist 98:1772-1778.
[doi:10.2138/am.2013.4509]

Link to Article