Tobias Steinpilz, Jens Teiser, and Gerhard Wurm
Astrophysical Journal 874, 60 Link to Article [DOI: 10.3847/1538-4357/ab07bb ]
University of Duisburg-Essen, Faculty of Physics, Lotharstr. 1-21D, Duisburg 47057, Germany

In the past, laboratory experiments and theoretical calculations showed a mismatch in the derived sticking properties of silicates in the context of planetesimal formation. It has been proposed by Kimura et al. that this mismatch is due to the value of the surface energy assumed, supposedly correlated to the presence or lack of water layers of different thickness on a grain’s surface. We present tensile strength measurements of dust aggregates with different water content here. The results are in support of the suggestion by Kimura et al. Dry samples show increased strengths by a factor of up to 10 over wet samples. A high value of γ = 0.2 J m⁻² likely applies to the dry low pressure conditions of protoplanetary disks and should be used in the future.

B. Zhao (赵斌)¹ and S. Q. Zhang (张双全)²
Astrophysical Journal 874, 5 Link to Article [DOI: 10.3847/1538-4357/ab0702 ]
¹School of Physics and Nuclear Energy Engineering, Beihang University Beijing 100191, People’s Republic of China
²School of Physics, Peking University, Beijing 100871, People’s Republic of China

The influence of the new mass model Weizsäcker–Skyrme 4 (WS4) on the r-process abundance distribution is investigated using the site-independent classical r-process and the site-dependent dynamical r-process models. The dynamical r-process calculations are performed under the neutrino-driven wind scenario. In comparison with the finite-range droplet model (FRDM) often used in r-process calculations, better agreement between the calculated abundance and the observed solar r-process abundance is found in both the classical and dynamical calculations by using the mass model WS4. The abundance underestimations at the A ~ 115, 140, and 200 mass regions encountered with the calculations using the FRDM is overcome to a large extent by using WS4.

¹K. Righter,²K. Pando,²D. K. Ross,³M. Righter,³T. J. Lapen
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13285]
¹NASA JSC, Mailcode XI2, 2101 NASA Pkwy, Houston, Texas, 77058 USA
²UTC–Jacobs JETS Contract, NASA JSC, Houston, Texas, 77058 USA
³Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas, 77204 USA
Published by arrangement with John Wiley & Sons

The depletion of volatile siderophile elements (VSE) Sn, Ag, Bi, Cd, and P in mantles of differentiated planetary bodies can be attributed to volatile‐depleted precursor materials (building blocks), fractionation during core formation, fractionation into and retention in sulfide minerals, and/or volatile loss associated with magmatism. Quantitative models to constrain the fractionation due to core formation have not been possible due to the lack of activity and partitioning data. Interaction parameters in Fe‐Si liquids have been measured at 1 GPa, 1600 °C and increase in the order Cd (~6), Ag (~10), Sn (~28), Bi (~46), and P (~58). These large and positive values contrast with smaller and negative values in Fe‐S liquids indicating that any chalcophile behavior exhibited by these elements will be erased by dissolution of a small amount of Si in the metallic liquid. A newly updated activity model is applied to Earth, Mars, and Vesta. Five elements (P, Zn, Sn, Cd, and In) in Earth’s primitive upper mantle can largely be explained by metal‐silicate equilibrium at high PT conditions where the core‐forming metal is a Fe‐Ni‐S‐Si‐C metallic liquid, but two other—Ag and Bi—become overabundant during core formation and require a removal mechanism such as late sulfide segregation. All of the VSE in the mantle of Mars are consistent with core formation in a volatile element depleted body, and do not require any additional processes. Only P and Ag in Vesta’s mantle are consistent with combined core formation and volatile‐depleted precursors, whereas the rest require accretion of chondritic or volatile‐bearing material after core formation. The concentrations of Zn, Ag, and Cd modeled for Vesta’s core are similar to the concentration range measured in magmatic iron meteorites indicating that these volatile elements were already depleted in Vesta’s precursor materials.

¹Mehmet Yesiltas,²Timothy D. Glotch,²Steven Jaret,³Alexander B. Verchovsky,³Richard C. Greenwood
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13287]
¹Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, 39100 Turkey
²Department of Geosciences, Stony Brook University, Stony Brook, New York, 11794 USA
³School of Physical Sciences, The Open University, Milton Keynes, MK7 6AA UK
Published by arrangement with John Wiley & Sons

As of today, the Sariçiçek (SC) meteorite is the newest howardite and the only confirmed fall among the 17 known howardites. In this study, we present isotopic, infrared, and Raman data on three distinct pieces of the SC meteorite. Our oxygen isotopic measurements show that Δ¹⁷O values of the pieces are close to each other, and are in good agreement with other howardites, eucrites, and diogenites. The carbon isotopic measurements, which were conducted by combusting terrestrial contamination selectively at temperatures lower than 500–600 °C, show the presence of indigenous carbon in the SC specimens. The matrix of these specimens, investigated via infrared microspectroscopy, appears to be dominated by clinopyroxene/orthopyroxene, forsterite, and fayalite, with minor contributions from ilmenite, plagioclase, and enstatite. Carbon‐rich regions were mapped and studied via Raman imaging microspectroscopy, which reveals that both amorphous and graphitic carbon exist in these samples. Synchrotron‐based infrared microspectroscopy data show the presence of very little aliphatic and aromatic hydrocarbons. The SC meteorite is suggested to be originating from the Antonia impact crater in the Rheasilvia impact basin on 4 Vesta (Unsalan et al. 2019). If this is in fact the case, then the carbon phases present in the SC samples might provide clues regarding the impactor material (e.g., carbonaceous chondrites).