Thomas-Keprta^a et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

^aJacobs, NASA Johnson Space Center, Mail Code JE-23, Building 31, Houston TX 77058

Carbonaceous matter on the surfaces of black pyroclastic beads, collected from Shorty crater during the Apollo 17 mission, represents the first identification of complex organic material associated with any lunar sample. We report the chemical, physical and isotopic properties of this organic matter that together support a pre-terrestrial origin. We suggest the most probable source is through the accretion of exogenous meteoritic kerogen from micrometeorite impacts into the lunar regolith. Abiotic organic matter has been continuously delivered to the surfaces of the terrestrial planets and their moons by accretion of asteroidal and cometary material. Determining the nature, distribution and evolution of such matter in the lunar regolith has important implications for understanding the prebiotic chemical inventory of the terrestrial planets.

Reference
Thomas-Keprta et al. (in press) Organic Matter on the Earth’s Moon. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2014.02.047]
Copyright Elsevier

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M. M. Woolfson

Physics Department, University of York, Heslington, York, YO10 5DD, UK

We currently do not have a copyright agreement with the publisher and cannot display the abstract here.

Reference
Woolfson MM (2013) A Postulated Planetary Collision, the Terrestrial Planets, the Moon and Smaller Solar-System Bodies. Earth, Moon, and Planets 111:1-14.
[doi:10.1007/s11038-013-9420-8]

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B. B. Ochsendorf¹, N. L. J. Cox², S. Krijt¹, F. Salgado¹, O. Berné⁴, J. P. Bernard⁴, L. Kaper³ and A. G. G. M. Tielens¹

¹Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden The Netherlands
²Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, bus 2401, 3001 Leuven, Belgium
³Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam, Science Park 904, PO Box 94249, 1090 GE Amsterdam, The Netherlands
⁴Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse, France

Observations obtained with the Spitzer Space Telescope and the WISE satellite have revealed a prominent arc-like structure at 50′′ (≃0.1 pc) from the O9.5V/B0.5V system σOri AB. We measure a total dust mass of 2.3 ± 1.5 × 10^-5  M_⊙. The derived dust-to-gas mass ratio is ≃0.29 ± 0.20. We attribute this dust structure to the interaction of radiation pressure from the star with dust carried along by the IC 434 photo-evaporative flow of ionized gas from the dark cloud L1630. We have developed a quantitative model for the interaction of a dusty ionized flow with nearby (massive) stars where radiation pressure stalls dust, piling it up at an appreciable distance (>0.1 pc), and force it to flow around the star. The model demonstrates that for the conditions in IC 434, the gas will decouple from the dust and will keep its original flow lines. Hence, we argue that this dust structure is the first example of a dust wave created by a massive star moving through the interstellar medium. Our model shows that for higher gas densities, coupling is more efficient and a bow wave will form, containing both dust and gas. Our model describes the physics of dust waves and bow waves and quantitatively reproduces the optical depth profile at 70 μm. Dust waves (and bow waves) stratify dust grains according to their radiation pressure opacity, which reflects the size distribution and composition of the grain material. It is found that in the particular case of σ Ori AB, dust is able to survive inside the ionized region. Comparison of our model results with observations implies that dust-gas coupling through Coulomb interaction is less important than previously thought, challenging our understanding of grain dynamics in hot, ionized regions of space. We describe the difference between dust (and bow) waves and classical bow shocks created by the interaction of a stellar wind with the interstellar medium. The results show that for late O-type stars with weak stellar winds, the stand-off distance of the resulting bow shock is very close to the star, well within the location of the dust wave. In general, we conclude that dust waves and bow waves should be common around stars showing the weak-wind phenomenon, i.e., stars with log(L/L_⊙)<5.2, and that these structures are best observed at mid-IR to FIR wavelengths, depending on the stellar spectral type. In particular, dust waves and bow waves are most efficiently formed around weak-wind stars moving through a high density medium. Moreover, they provide a unique opportunity to study the direct interaction between a (massive) star and its immediate surroundings.

Reference
Ochsendorf BB, Cox NLJ, Krijt S, Salgado F, Berné O, Bernard JP, Kaper L and Tielens AGGM (2014) Blowing in the wind: The dust wave around σ Orionis AB. Astronomy & Astrophysics 563:A65.
[doi:10.1051/0004-6361/201322873]
Reproduced with permission © ESO

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Catherine Walsh^1,2, Tom. J. Millar², Hideko Nomura^3,4,5, Eric Herbst^6,7, Susanna Widicus Weaver⁸, Yuri Aikawa⁹, Jacob C. Laas⁸ and Anton I. Vasyunin^10,11

¹Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
²Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, University Road, Belfast BT7 1NN, UK
³Department of Astronomy, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan
⁴National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan
⁵Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, 152-8551 Tokyo, Japan
⁶Departments of Physics, Chemistry and Astronomy, The Ohio State University, Columbus OH 43210, USA
⁷Departments of Chemistry, Astronomy, and Physics, University of Virginia, Charlottesville VA 22904, USA
⁸Department of Chemistry, Emory University, Atlanta GA 30322, USA
⁹Department of Earth and Planetary Sciences, Kobe University, 1-1 Rokkodai-cho, Nada, 657-8501 Kobe, Japan
¹⁰Department of Chemistry, University of Virginia, Charlottesville VA 22904, USA
¹¹Visiting Scientist, Ural Federal University, 620075 Ekaterinburg, Russia

Context. Protoplanetary disks are vital objects in star and planet formation, possessing all the material, gas and dust, which may form a planetary system orbiting the new star. Small, simple molecules have traditionally been detected in protoplanetary disks; however, in the ALMA era, we expect the molecular inventory of protoplanetary disks to significantly increase.
Aims. We investigate the synthesis of complex organic molecules (COMs) in protoplanetary disks to put constraints on the achievable chemical complexity and to predict species and transitions which may be observable with ALMA.
Methods. We have coupled a 2D steady-state physical model of a protoplanetary disk around a typical T Tauri star with a large gas-grain chemical network including COMs. We compare the resulting column densities with those derived from observations and perform ray-tracing calculations to predict line spectra. We compare the synthesised line intensities with current observations and determine those COMs which may be observable in nearby objects. We also compare the predicted grain-surface abundances with those derived from cometary comae observations.
Results. We find COMs are efficiently formed in the disk midplane via grain-surface chemical reactions, reaching peak grain-surface fractional abundances ~10^-6–10^-4 that of the H nuclei number density. COMs formed on grain surfaces are returned to the gas phase via non-thermal desorption; however, gas-phase species reach lower fractional abundances than their grain-surface equivalents, ~10^-12–10^-7. Including the irradiation of grain mantle material helps build further complexity in the ice through the replenishment of grain-surface radicals which take part in further grain-surface reactions. There is reasonable agreement with several line transitions of H₂CO observed towards T Tauri star-disk systems. There is poor agreement with HC₃N lines observed towards LkCa 15 and GO Tau and we discuss possible explanations for these discrepancies. The synthesised line intensities for CH₃OH are consistent with upper limits determined towards all sources. Our models suggest CH₃OH should be readily observable in nearby protoplanetary disks with ALMA; however, detection of more complex species may prove challenging, even with ALMA “Full Science” capabilities. Our grain-surface abundances are consistent with those derived from cometary comae observations providing additional evidence for the hypothesis that comets (and other planetesimals) formed via the coagulation of icy grains in the Sun’s natal disk.

Reference
Walsh C, Millar TJ, Nomura H, Herbst E, Weaver SW, Aikawa Y, Laas JC and Vasyunin AI (2014) Complex organic molecules in protoplanetary disks. Astronomy & Astrophysics 563:A33.
[doi:10.1051/0004-6361/201322446]
Reproduced with permission © ESO

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