2012 Annual Science Report
Arizona State University Reporting | SEP 2011 – AUG 2012
Astrophysical Controls on the Elements of Life, Task 1: High-Precision Isotopic Studies of Meteorites
The initial Solar System abundances of the short-lived radionuclides (SLRs) 26Al (half life ~0.73 Ma) and 60Fe (half life ~2.6 Ma) are important to constrain since, if present in sufficient abundance, these SLRs served as heat sources for dehydration and differentiation processes on planetary bodies. The implications for this work include the astrophysical environment in which the Sun formed, and the abundance of water on the terrestrial planets.
The main focus of our efforts under Task 1 during this reporting period has been on identification of refractory inclusions in chondrites with fractionation and unknown Nuclear (FUN) effects. The ultimate goal of this project is to identify FUN inclusions for precise age dating, which would potentially allow us to constrain the timing of 26Al injection into the early Solar System. During this reporting period, we completed development of the analytical methodologies for high precision Ti isotope analyses by laser ablation multicollector inductively coupled plasma mass spectrometer, since FUN inclusions are known to contain large mass independent isotope effects in a variety of elements including Ti. Subsequently, the Ti isotopic compositions of almost two dozen refractory inclusions from the Allende CV3 carbonaceous chondrites were analyzed, and one inclusion was identified as a FUN CAI (CMS-1). Initial petrographic characterization has been performed and, in addition to Ti isotopic composition, Mg and Si isotopes were also measured in this inclusion. Graduate student Curtis Williams is conducting this work under the supervision of Co-I Meenakshi Wadhwa; two conference abstracts were submitted.
We additionally made significant progress towards completing the project on placing constraints on the initial abundance of 60Fe in the early Solar System. If present in sufficient abundance (i.e., 60Fe/56Fe >~5 ×10-7), this radionuclide would serve as a “smoking gun” for the late injection of 60Fe by a supernova into the early Solar System, and as a significant heat source for the dehydration/differentiation of planetesimals. This work was conducted primarily by graduate student Lev Spivak-Birndorf (who was funded during this reporting period by a NESSF award, and defended his PhD thesis in August 2012) under the supervision of Co-I Meenakshi Wadhwa; three conference abstracts were submitted and a manuscript is currently under preparation.