^1,2T. J. Barrett,^1,3A. J. King,¹G. Degli-Alessandrini,⁴S. J. Hammond,³E. Humphreys-Williams,³B. Schmidt,¹R. C. Greenwood,¹F. A. J. Abernethy,^1,3M. Anand,⁵E. Rudnickaitė
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14229]
¹School of Physical Sciences, The Open University, Milton Keynes, UK
²Center for Lunar Science and Exploration, Lunar and Planetary Institute, Houston, Texas, USA
³Planetary Materials Group, Natural History Museum, London, UK
⁴School of Environment, Earth, and Ecosystem Sciences, The Open University, Milton Keynes, UK
⁵Department of Geology and Mineralogy, Museum of Geology of Vilnius University, Vilnius, Lithuania
Published by arrangement with John Wiley & Sons

The Padvarninkai meteorite is a relatively understudied eucrite, initially misclassified as a shergottite given its strong shock characteristics. In this study, a comprehensive examination of the petrology; mineral composition; major, minor, and trace element abundances; and isotopic composition (C, O) is presented. Padvarninkai is a monomict eucrite consisting of a fine to coarse-grained lithology and impact melt veins. Pyroxene grains are typically severely fractured and mosaicked whilst plagioclase is either partially or totally converted to maskelynite. Based on shock features observed in pyroxene, plagioclase, and apatite, Padvarninkai can be given a shock classification of M-S4/5. Despite the high shock experienced by this sample, some of the original igneous textures remain. Compositionally, Padvarninkai is a main group eucrite with a flat REE pattern (~10–12 × CI) and elevated Ni abundances. Whilst both new and literature oxygen isotopes are similar to other eucrites, however, Padvarninkai displays an anomalously high δ13C value. To reconcile the high Ni and δ13C value, impact contamination modeling was conducted. These models could not reconcile both the high Ni and δ13C value with the eucritic δ18O values, arguing against impact as a source for these anomalies.

¹Bidong Zhang,²Nancy L. Chabot,¹Alan E. Rubin
Proceedings of the National Academy of Sciences of the United States of America (PNAS) 121, e2306995121 Link to Article [https://doi.org/10.1073/pnas.23069951]
¹Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, CA 90095-1567
²Space Exploration Sector, Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723

Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System, and they preserve information about conditions and planet-forming processes in the solar nebula. In this study, we include comprehensive elemental compositions and fractional-crystallization modeling for iron meteorites from the cores of five differentiated asteroids from the inner Solar System. Together with previous results of metallic cores from the outer Solar System, we conclude that asteroidal cores from the outer Solar System have smaller sizes, elevated siderophile-element abundances, and simpler crystallization processes than those from the inner Solar System. These differences are related to the formation locations of the parent asteroids because the solar protoplanetary disk varied in redox conditions, elemental distributions, and dynamics at different heliocentric distances. Using highly siderophile-element data from iron meteorites, we reconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across the protoplanetary disk within the first million years of Solar-System history. CAIs, the first solids to condense in the Solar System, formed close to the Sun. They were, however, concentrated within the outer disk and depleted within the inner disk. Future models of the structure and evolution of the protoplanetary disk should account for this distribution pattern of CAIs.