^1,2Oliver Shah,¹Ravit Helled,²Yann Alibert,^2,3Klaus Mezger
The Astrophysical Journal 926, 2 Open Access Link to Article [DOI 10.3847/1538-4357/ac410d]
¹Center for Theoretical Astrophysics and Cosmology, University of Zurich, Switzerland
²Center for Space and Habitability, University of Bern, Switzerland
³Institut für Geologie, University of Bern, Switzerland

Venus’ mass and radius are similar to those of Earth. However, dissimilarities in atmospheric properties, geophysical activity, and magnetic field generation could hint toward significant differences in the chemical composition and interior evolution of the two planets. Although various explanations for the differences between Venus and Earth have been proposed, the currently available data are insufficient to discriminate among the different solutions. Here we investigate the possible range of models for Venus’ structure. We assume that core segregation happened as a single-stage event. The mantle composition is inferred from the core composition using a prescription for metal-silicate partitioning. We consider three different cases for the composition of Venus defined via the bulk Si and Mg content, and the core’s S content. Permissible ranges for the core size, mantle, and core composition as well as the normalized moment of inertia (MoI) are presented for these compositions. A solid inner core could exist for all compositions. We estimate that Venus’ MoI is 0.317–0.351 and its core size 2930–4350 km for all assumed compositions. Higher MoI values correspond to more oxidizing conditions during core segregation. A determination of the abundance of FeO in Venus’ mantle by future missions could further constrain its composition and internal structure. This can reveal important information on Venus’ formation and evolution, and, possibly, the reasons for the differences between Venus and our home planet.

^{9, 1}Jacqueline den Hartogh,¹Maria K. Petö,^9,1,2,3Thomas Lawson,^4,5Andre Sieverding,^1,6Hannah Brinkman,^9,1,2,3Marco Pignatari,^1,7,8Maria Lugaro
The Astrophysical Journal 927, 220 Open Access Link to Article [DOI 10.3847/1538-4357/ac4965]
¹Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network (ELKH), Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary
²E.A. Milne Centre for Astrophysics, Department of Physics and Mathematics, University of Hull, HU6 7RX, UK
³Joint Institute for Nuclear Astrophysics—Center for the Evolution of the Elements, USA
⁴School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
⁵Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6354, USA
⁶Graduate School of Physics, University of Szeged, Dom tér 9, Szeged, 6720, Hungary
⁷ELTE Eötvös Loránd University, Institute of Physics, Budapest 1117, Pázmány Péter sétány 1/A, Hungary
⁸School of Physics and Astronomy, Monash University, VIC 3800, Australia

Isotope variations of nucleosynthetic origin among solar system solid samples are well documented, yet the origin of these variations is still uncertain. The observed variability of ⁵⁴Cr among materials formed in different regions of the protoplanetary disk has been attributed to variable amounts of presolar, chromium-rich oxide (chromite) grains, which exist within the meteoritic stardust inventory and most likely originated from some type of supernova explosion. To investigate if core-collapse supernovae (CCSNe) could be the site of origin of these grains, we analyze yields of CCSN models of stars with initial masses 15, 20, and 25 M_⊙, and solar metallicity. We present an extensive abundance data set of the Cr, Mg, and Al isotopes as a function of enclosed mass. We find cases in which the explosive C ashes produce a composition in good agreement with the observed ⁵⁴Cr/⁵²Cr and ⁵³Cr/⁵²Cr ratios as well as the ⁵⁰Cr/⁵²Cr ratios. Taking into account that the signal at atomic mass 50 could also originate from ⁵⁰Ti, the ashes of explosive He burning also match the observed ratios. Addition of material from the He ashes (enriched in Al and Cr relative to Mg to simulate the make-up of chromite grains) to the solar system’s composition may reproduce the observed correlation between Mg and Cr anomalies, while material from the C ashes does not present significant Mg anomalies together with Cr isotopic variations. In all cases, nonradiogenic, stable Mg isotope variations dominate over the variations expected from ²⁶Al.