¹L. Ilsedore Cleeves, ²Edwin A. Bergin, ³Conel M. O’D. Alexander, ²Fujun Du, ¹Dawn Graninger, ¹Karin I. Öberg, ⁴Tim J. Harries
The Astrophysical Journal, Volume 819, Number 1 Link to Article [http://dx.doi.org/10.3847/0004-637X/819/1/13]
¹Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
²Department of Astronomy, University of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109, USA
³DTM, Carnegie Institution of Washington, Washington, DC 20015, USA
⁴Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK

Deuterium-to-hydrogen (D/H) enrichments in molecular species provide clues about their original formation environment. The organic materials in primitive solar system bodies generally have higher D/H ratios and show greater D/H variation when compared to D/H in solar system water. We propose this difference arises at least in part due to (1) the availability of additional chemical fractionation pathways for organics beyond that for water, and (2) the higher volatility of key carbon reservoirs compared to oxygen. We test this hypothesis using detailed disk models, including a sophisticated, new disk ionization treatment with a low cosmic-ray ionization rate, and find that disk chemistry leads to higher deuterium enrichment in organics compared to water, helped especially by fractionation via the precursors CH2D+/CH3+. We also find that the D/H ratio in individual species varies significantly depending on their particular formation pathways. For example, from ~20–40 au, CH4 can reach ${\rm{D}}/{\rm{H}}\sim 2\times {10}^{-3}$, while D/H in CH3OH remains locally unaltered. Finally, while the global organic D/H in our models can reproduce intermediately elevated D/H in the bulk hydrocarbon reservoir, our models are unable to reproduce the most deuterium-enriched organic materials in the solar system, and thus our model requires some inheritance from the cold interstellar medium from which the Sun formed.

¹F. Fontani, ¹V. M. Rivilla, ²P. Caselli, ^2,3A. Vasyunin, ⁴A. Palau
The Astrophysical Journal Letters 822,L30 Link to Article [http://dx.doi.org/10.3847/2041-8205/822/2/L30]
¹INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze, Italy
²Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse, D-85748 Garching, Germany
³Ural Federal University, Ekaterinburg, Russia
⁴Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, P.O. Box 3-72, 58090 Morelia, Michoacán, México

Phosphorus is a crucial element for the development of life, but so far P-bearing molecules have been detected only in a few astrophysical objects; hence, its interstellar chemistry is almost totally unknown. Here, we show new detections of phosphorus nitride (PN) in a sample of dense cores in different evolutionary stages of the intermediate- and high-mass star formation process: starless, with protostellar objects, and with ultracompact H ii regions. All detected PN line widths are smaller than sime5 km s−1, and they arise from regions associated with kinetic temperatures smaller than 100 K. Because the few previous detections reported in the literature are associated with warmer and more turbulent sources, the results of this work show that PN can arise from relatively quiescent and cold gas. This information is challenging for theoretical models that invoke either high desorption temperatures or grain sputtering from shocks to release phosphorus into the gas phase. Derived column densities are of the order of 1011–12 cm−2, marginally lower than the values derived in the few high-mass star-forming regions detected so far. New constraints on the abundance of phosphorus monoxide, the fundamental unit of biologically relevant molecules, are also given.

¹S. De Angelis, ¹P. Manzari, ¹M.C. De Sanctis, ^1,2E. Ammannito, ^1,3T. Di Iorio
Icarus (in Press) Link to Article [doi:10.1016/j.icarus.2016.07.002]
¹Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Rome, Italy
²University of California Los Angeles, Earth Planetary and Space Sciences, Los Angeles, CA-90095, USA
³ENEA SSPT-PROTER-OAC, Roma, Italy
Copyright Elsevier

Carbonates and clay minerals are present in Solar System bodies such as Mars and asteroid (1) Ceres. Brucite has been proposed in the recent past to fit absorption features in spectra of Ceres. In this study Visible-Near Infrared reflectance spectroscopic measurements have been performed on brucite-carbonate-clay minerals mixtures, in the 0.2-5.1 μm spectral range. Different sets of three- and two-components mixtures have been prepared using these three fine powdered endmembers, by varying the relative proportions of carbonate, clay and brucite. Spectra have been acquired on the endmembers components separately and on the mixtures. Absorption features diagnostic of the carbonate, clay and brucite phases have been analyzed and band parameters (position, depth, area, width) determined. Several trends and correlations with mineral phase content in each mixture have been investigated, with the aim to determining how endmember components influence the mixture spectra and their minimum detectability threshold. Our results indicate that brucite is detectable in mineral mixtures with carbonates and clays, based on its main absorption features at 0.95, 2.45-2.47 and 3.05 μm. While the 0.95 and 3.05-μm features are only discernible for very high brucite contents in the mixtures, the ∼2.45-μm band turns out to be highly diagnostic, also for very small amounts of brucite (of the order of 10 wt%). These experiments, together with DAWN observations of Ceres, substantially rule out the presence of great amounts of brucite globally distributed on the surface of Ceres.