Effective January 1, 2011, LPI seminars will be held on Fridays.
LPI seminars are held from 3:30–4:30 p.m. in the Lecture Hall at USRA, 3600 Bay Area Boulevard, Houston, Texas. Refreshments are served at 4:30 p.m. For more information, please contact Georgiana Kramer (phone: 281-486-2141; e-mail: firstname.lastname@example.org) or Patricia Craig (phone: 281-486-2144; e-mail: email@example.com). A map of the Clear Lake area is available here. This schedule is subject to revision.
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In this talk, I will present the new 41Ca-41K isotopic data of two Type A CAIs, NWA 3118 #1Nb (compact Type A) and Vigarano 3138 F8 (Fluffy Type A), from reduced CV3 chondrites. The NWA CAI is found to have carried live 41Ca at the level of (4.6±1.9)×10−9, consistent with the proposed Solar System initial 41Ca/40Ca = 4.2 × 10−9 by Liu et al. (2012). On the other hand, the Vigarano CAI does not have resolvable radiogenic 41K excesses that can be attributed to the decay of 41Ca. Combined with the 26Al data that have been reported for these two CAIs, we infer that the 41Ca distribution was not homogeneous when 26Al was widespread at the canonical level of 26Al/27Al = 5.2 × 10−5. Such a 41Ca heterogeneity can be understood under two astrophysical contexts: in- situ charged particle irradiation by the protoSun in the solar nebula that had inherited some baseline 10Be abundance from the molecular cloud, and Solar System formation in a molecular cloud enriched in 26Al and 41Ca contaminated by massive star winds. That said, more high quality 41Ca data are still needed to better understand the origin of this radionuclide.
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