Klaus M. Pontoppidan¹, Colette Salyk², Andrea Banzatti³, Geoffrey A. Blake⁴, Catherine Walsh⁵, John H. Lacy⁶, and Matthew J. Richter⁷
Astrophysical Journal 874, 92 Link to Article [DOI: 10.3847/1538-4357/ab05d8 ]
¹Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
²Vassar College Physics and Astronomy Department, 124 Raymond Avenue, Poughkeepsie, NY 12604, USA
³Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, USA
⁴Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, 1200 E California Boulevard, Pasadena, CA 91125, USA
⁵School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
⁶Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712, USA
⁷Department of Physics, University of California Davis, 1 Shields Avenue, Davis, CA 95616, USA

The dominant reservoirs of elemental nitrogen in protoplanetary disks have not yet been observationally identified. Likely candidates are HCN, NH₃, and N₂. The relative abundances of these carriers determine the composition of planetesimals as a function of disk radius due to strong differences in their volatility. A significant sequestration of nitrogen in carriers less volatile than N₂ is likely required to deliver even small amounts of nitrogen to the Earth and potentially habitable exoplanets. While HCN has been detected in small amounts in inner disks (<10 au), so far only relatively insensitive upper limits on inner disk NH₃ have been obtained. We present new Gemini-TEXES high-resolution spectroscopy of the 10.75 μm band of warm NH₃, and use two-dimensional radiative transfer modeling to improve previous upper limits by an order of magnitude to at 1 au. These NH₃ abundances are significantly lower than those typical for ices in circumstellar envelopes (). We also consistently retrieve the inner disk HCN gas abundances using archival Spitzer spectra, and derive upper limits on the HCN ice abundance in protostellar envelopes using archival ground-based 4.7 μm spectroscopy ([HCN_ice]/[H₂O_ice] < 1.5%–9%). We identify the NH₃/HCN ratio as an indicator of chemical evolution in the disk, and we use this ratio to suggest that inner disk nitrogen is efficiently converted from NH₃ to N₂, significantly increasing the volatility of nitrogen in planet-forming regions.

¹Y.Kebukawa et al. (>10)
Scientific Reports 9, 3169 Link to Article [DOI: 10.1038/s41598-019-39357-1]
¹Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan

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¹M.A.Fitzgerald,²K.B.Knight,²J.E.Matzel,¹K.R.Czerwinski
Chemical Geology 507,96-119 Link to Article [https://doi.org/10.1016/j.chemgeo.2018.12.018]
¹University of Nevada Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV 89154, USA
²Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA

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¹Trey A.Lobpries,¹Thomas J.Lapen
Journal of African Earth Sciences 150,673-684 Link to Article [https://doi.org/10.1016/j.jafrearsci.2018.09.020]
¹Department of Earth and Atmospheric Sciences, University of Houston, 312 Science and Research 1, 3507 Cullen Blvd, Rm. 312, Houston, TX, 77204, USA

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¹Abhishek K.Rai,^1,2Jayanta K.Pati,³Rohit Kumar
Optics&Laser Technology 114, 146-157 Link to Article [https://doi.org/10.1016/j.optlastec.2019.01.028]
¹Department of Earth and Planetary Sciences, Nehru Science Centre, University of Allahabad, Allahabad 211 002, India
²National Center of Experimental Mineralogy and Petrology, 14, Chatham Lines, University of Allahabad, Allahabad 211 002, India
³Department of Physics, C.M.P. Degree College, University of Allahabad, Allahabad 211 002, India

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^1,2Sergey N. Britvin,³Vladimir V. Shilovskikh,⁴Renato Pagano,³Natalia S. Vlasenko,⁵Anatoly N. Zaitsev,⁵Maria G. Krzhizhanovskaya,³Maksim S. Lozhkin,⁵Andrey A. Zolotarev,⁵Vladislav V. Gurzhiy
Scientific Reports 9, 1047 Link to Article [https://doi.org/10.1038/s41598-018-37795-x]
¹Institute of Earth Sciences, Saint-Petersburg State University, Universitetskaya Nab. 7/9, 199034, St. Petersburg, Russia
²Kola Science Center of Russian Academy of Sciences, Fersman Str. 14, 184209, Apatity, Murmansk Region, Russia
³Centre for Geo-Environmental Research and Modelling, Saint-Petersburg State University, Ulyanovskaya ul. 1, 198504, St. Petersburg, Russia
⁴Casella Postale 37, Cinisello, Milano, Italy
⁵Institute of Earth Sciences, Saint-Petersburg State University, Universitetskaya Nab. 7/9, 199034, St. Petersburg, Russia

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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).