Y. Alibert^1,2, F. Carron¹, A. Fortier¹, S. Pfyffer¹, W. Benz¹, C. Mordasini³ and D. Swoboda¹

¹Physikalisches Institut & Center for Space and Habitability, Universität Bern, 3012 Bern, Switzerland
²Observatoire de Besançon, 41 avenue de l’Observatoire, 25000 Besançon, France
³Max-Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany

Context. Planet formation models have been developed during the past years to try to reproduce what has been observed of both the solar system and the extrasolar planets. Some of these models have partially succeeded, but they focus on massive planets and, for the sake of simplicity, exclude planets belonging to planetary systems. However, more and more planets are now found in planetary systems. This tendency, which is a result of radial velocity, transit, and direct imaging surveys, seems to be even more pronounced for low-mass planets. These new observations require improving planet formation models, including new physics, and considering the formation of systems.
Aims. In a recent series of papers, we have presented some improvements in the physics of our models, focussing in particular on the internal structure of forming planets, and on the computation of the excitation state of planetesimals and their resulting accretion rate. In this paper, we focus on the concurrent effect of the formation of more than one planet in the same protoplanetary disc and show the effect, in terms of architecture and composition of this multiplicity.
Methods. We used an N-body calculation including collision detection to compute the orbital evolution of a planetary system. Moreover, we describe the effect of competition for accretion of gas and solids, as well as the effect of gravitational interactions between planets.
Results. We show that the masses and semi-major axes of planets are modified by both the effect of competition and gravitational interactions. We also present the effect of the assumed number of forming planets in the same system (a free parameter of the model), as well as the effect of the inclination and eccentricity damping. We find that the fraction of ejected planets increases from nearly 0 to 8% as we change the number of embryos we seed the system with from 2 to 20 planetary embryos. Moreover, our calculations show that, when considering planets more massive than ~5 M_⊕, simulations with 10 or 20 planetary embryos statistically give the same results in terms of mass function and period distribution.

Reference
Alibert Y, Carron F, Fortier A, Pfyffer S, Benz W, Mordasini C and Swoboda D (in press) Theoretical models of planetary system formation: mass vs. semi-major axis. Astronomy & Astrophysics
[doi:10.1051/0004-6361/201321690]
Reproduced with permission © ESO

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Daniel Clery

We currently seek a copyright agreement with Science to display abstracts of their cosmochemistry related publications.

Reference
Clery D (2013) Impact Theory Gets Whacked. Science  342:183-185.
[doi:10.1126/science.342.6155.183]

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J. Farihi^1,*, B. T. Gänsicke², D. Koester³

We currently seek a copyright agreement with Science to display abstracts of their cosmochemistry related publications.

Reference
Farihi J, Gänsicke BT and Koester D (2013) Evidence for Water in the Rocky Debris of a Disrupted Extrasolar Minor Planet. Science  342:218-220.
[doi:10.1126/science.1239447]

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J.A. Barrat^a,*, A. Jambon^b, L. Ferrière^c, C. Bollinger^d, J.A. Langlade^d, C. Liorzou^a, O. Boudouma^b, M. Fialin^b

^aUniversité de Brest, CNRS UMR 6538 (Domaines Océaniques), I.U.E.M., Place Nicolas Copernic, 29280 Plouzané, France
^bUniversité Pierre et Marie Curie-Paris 6 ISTeP, CNRS UMR 7193, case 110, 4 place Jussieu, 75252 Paris cedex 05, France
^cNatural History Museum, Burgring 7, A-1010 Vienna, Austria
^dCNRS UMS 3113, I.U.E.M., Place Nicolas Copernic, 29280 Plouzané Cedex, France

We report on the major and trace element geochemistry of the impact melts contained in some shergottite meteorites. It has been previously proposed that some of these impact melts formed from a mixture of the host rock and a Martian soil component (e.g., Rao et al., 1999) or from partially weathered portions of the host rock (Chennaoui Aoudjehane et al., 2012). Our results contradict both of these theories. Trace element abundances of a glass pod from the EETA 79001A meteorite are identical to those of the host lithology, and indicate that no additional component is required in this case. The impact melts in Tissint share the same trace element features as the host rock, and no secondary phases produced by Martian secondary processes are involved. The light rare earth enrichments displayed by two small samples of Tissint (Chennaoui Aoudjehane et al., 2012) are possibly the result of some contamination of small stones on desert soil before the recovery of the meteorites.

Reference
Barrat JA, Jambon A, Ferrière L, Bollinger C, Langlade JA, Liorzou C, Boudouma O and Fialin M (in press) No Martian soil component in shergottite meteorites. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2013.09.033]
Copyright Elsevier

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Roger H. Hewins^a,b,*, Brigitte Zanda^a, Hugues Leroux^c, Jean-Alix Barrat^d, Munir Humayun^e, Christa Göpel^f, Richard C. Greenwood^g, Ian A. Franchi^g, Sylvain Pont^a, Jean-Pierre Lorand^h, Cécile Cournèdeⁱ, Jérôme Gattacceca^i,j, Pierre Rochetteⁱ, Maïa Kuga^k, Yves Marrocchi^k, Bernard Marty^k

^aLabo. de Minéralogie et Cosmochimie du Muséum, MNHN and CNRS UMR 7202, 75005 Paris, France
^bDept. of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
^cUnité Matériaux et Transformations, Université Lille 1 and CNRS, UMR8207, F-59655 Villeneuve d’Ascq, France
^dUniversité Européenne de Bretagne and CNRS UMR 6538, U.B.O-I.U.E.M., 29280 Plouzané Cedex, France
^eDept. of Earth, Ocean and Atmospheric Science and National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
^fInstitut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154 CNRS, F-75005 Paris, France
^gPSS, Open University, Walton Hall, Milton Keynes MK7 6AA, UK
^hLaboratoire de Planétologie et Géodynamique LPG Nantes – UMR CNRS 6112, 44322 Nantes Cedex 3, France
ⁱCNRS/Aix-Marseille Université, CEREGE UM34, 13545 Aix-en-Provence, France
^jDepartment of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
^kUniversité Lorraine and CNRS, CRPG, UPR 2300, Vandoeuvre les Nancy, F-54501, France

The Paris chondrite provides an excellent opportunity to study CM chondrules and refractory inclusions in a more pristine state than currently possible from other CMs, and to investigate the earliest stages of aqueous alteration captured within a single CM bulk composition. It was found in the effects of a former colonial mining engineer and may have been an observed fall. The texture, mineralogy, petrography, magnetic properties and chemical and isotopic compositions are consistent with classification as a CM2 chondrite. There are ~45 vol% high-temperature components mainly Type I chondrules (with olivine mostly Fa_0-2, mean Fa_0.9) with granular textures because of low mesostasis abundances. Type II chondrules contain olivine Fa₇ to Fa₇₆. These are dominantly of Type IIA, but there are IIAB and IIB chondrules, II(A)B chondrules with minor highly ferroan olivine, and IIA(C) with augite as the only pyroxene. The refractory inclusions in Paris are amoeboid olivine aggregates (AOA) and fine-grained spinel-rich Ca-Al-rich inclusions (CAI). The CAI phases formed in the sequence hibonite, perovskite, grossite, spinel, gehlenite, anorthite, diopside/fassaite and forsterite. The most refractory phases are embedded in spinel, which also occurs as massive nodules. Refractory metal nuggets are found in many CAI and refractory platinum group element abundances (PGE) decrease following the observed condensation sequences of their host phases. Mn-Cr isotope measurements of mineral separates from Paris define a regression line with a slope of ⁵³Mn/⁵⁵Mn = (5.76±0.76)×10⁶. If we interpret Cr isotopic systematics as dating Paris components, particularly the chondrules, the age is 4566.44 ± 0.66 Myr, which is close to the age of CAI and puts new constraints on the early evolution of the solar system. Eleven individual Paris samples define an O isotope mixing line that passes through CM2 and CO3 falls and indicates that Paris is a very fresh sample, with variation explained by local differences in the extent of alteration. The anhydrous precursor to the CM2s was CO3-like, but the two groups differed in that the CMs accreted a higher proportion of water. Paris has little matrix (~47%, plus 8% fine grained rims) and is less altered than other CM chondrites. Chondrule silicates (except mesostasis), CAI phases, submicron forsterite and amorphous silicate in the matrix are all well preserved in the freshest domains, and there is abundant metal preserved (metal alteration stage 1 of Palmer E. E. and D. S. Lauretta (2011) Aqueous alteration of kamacite in CM chondrites, Meteor. Planet. Sci. 46, 1587–1607). Metal and sulfide compositions and textures correspond to the least heated or equilibrated CM chondrites, Category A of Kimura M., Grossman J. N. and Weisberg M. K. (2011) Fe-Ni metal and sulfide minerals in CM chondrites, An indicator for thermal history.Meteor. Planet. Sci. 46, 431–442. The composition of tochilinite-cronstedtite intergrowths gives a PCP index of ~2.9. Cronstedtite is more abundant in the more altered zones whereas in normal highly altered CM chondrites, with petrologic subtype 2.6-2.0 based on the S/SiO₂ and ∑FeO/SiO₂ ratios in PCP or tochilinite-cronstedtite intergrowths (Rubin A. E., Trigo-Rodrıguez J. M., Huber H. and Wasson J. T. (2007) Progressive aqueous alteration of CM carbonaceous chondrites Geochim. Cosmochim. Acta 71, 2361-2382), cronstedtite is destroyed by alteration. The matrix in fresh zones has CI chondritic volatile element abundances, but interactions between matrix and chondrules occurred during alteration, modifying the volatile element abundances in the altered zones. Paris has higher trapped Ne contents, more primitive organic compounds, and more primitive organic material than other CMs. There are gradational contacts between domains of different degree of alteration, on the scale of ~1 cm, but also highly altered clasts, suggesting mainly a water-limited style of alteration, with no significant metamorphic reheating.

Reference
Hewins RH, Zanda B, Leroux H, Barrat J-A, Humayun M, Göpel C, Greenwood RC, Franchi IA, Pont S, Lorand J-P, Cournède C, Gattacceca J, Rochette P, Kuga M, Marrocchi Y and Marty B (in press) The Paris meteorite, the least altered CM chondrite so far. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2013.09.014]
Copyright Elsevier

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T. G. Müller¹, T. Miyata², C. Kiss³, M. A. Gurwell⁴, S. Hasegawa⁵, E. Vilenius¹, S. Sako², T. Kamizuka², T. Nakamura⁶, K. Asano², M. Uchiyama², M. Konishi², M. Yoneda⁷, T. Ootsubo⁸, F. Usui⁵, Y. Yoshii², M. Kidger⁹, B. Altieri⁹, R. Lorente⁹, A. Pál³, L. O’Rourke⁹ and L. Metcalfe⁹

¹Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, Postfach 1312, 85741 Garching, Germany
²Institute of Astronomy, School of Science, the University of Tokyo, 2-21-1 Osawa, Mitaka, 181-0015 Tokyo, Japan
³Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege 15-17, 1121 Budapest, Hungary
⁴Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁵Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, 229-8510 Kanagawa, Japan
⁶Department of Astronomy, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-0033 Tokyo, Japan
⁷Planetary Plasma and Atmospheric Research Center, Tohoku University, Aramaki, Aoba-ku, 980-8578 Sendai, Japan
⁸Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, 980-8578 Sendai, Japan
⁹European Space Astronomy Centre (ESAC), European Space Agency, Apartado de Correos 78, 28691 Villanueva de la Cañada, Madrid, Spain

The near-Earth asteroid 308635 (2005 YU₅₅) is a potentially hazardous asteroid which was discovered in 2005 and passed Earth on Nov. 8, 2011 at 0.85 lunar distances. This was the closest known approach by an asteroid of several hundred metres in diameter since 1976 when an object of similar size passed at 0.5 lunar distances. We observed 2005 YU₅₅ from the ground with a recently developed mid-IR camera (miniTAO/MAX38) in N and Q bands and with the Submillimeter Array (SMA) at 1.3 mm. In addition, we obtained space observations with Herschel/PACS at 70, 100, and 160 μm. Our thermal measurements cover a wide range of wavelengths from 8.9 μm to 1.3 mm and were taken after opposition at phase angles between –97° and –18°. We performed a radiometric analysis via a thermophysical model and combined our derived properties with results from radar, adaptive optics, lightcurve observations, speckle, and auxiliary thermal data. We find that 308635 (2005 YU₅₅) has an almost spherical shape with an effective diameter of 300 to 312 m and a geometric albedo p_V of 0.055 to 0.075. Its spin axis is oriented towards celestial directions (λ_ecl, β_ecl) = (60° ± 30°, –60° ± 15°), which means it has a retrograde sense of rotation. The analysis of all available data combined revealed a discrepancy with the radar-derived size. Our radiometric analysis of the thermal data together with the problem to find a unique rotation period might be connected to a non-principal axis rotation. A low to intermediate level of surface roughness (rms mean slope in the range 0.1–0.3) is required to explain the available thermal measurements. We found a thermal inertia in the range 350−800 Jm^-2 s^-0.5 K^-1, very similar to the rubble-pile asteroid 25 143 Itokawa and indicating a surface with a mixture of low conductivity fine regolith with larger rocks and boulders of high thermal inertia.

Reference
Müller TG, Miyata T, Kiss C, Gurwell MA, Hasegawa S, Vilenius E, Sako S, Kamizuka T, Nakamura T, Asano K, Uchiyama M, Konishi M, Yoneda M, Ootsubo T, Usui F, Yoshii Y, Kidger M, Altieri B, Lorente R, Pál A, O’Rourke L, and Metcalfe L (in press) Physical properties of asteroid 308635 (2005 YU55) derived from multi-instrument infrared observations during a very close Earth approach. Astronomy & Astrophysics
[doi:10.1051/0004-6361/201321664]
Reproduced with permission © ESO

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C. T. Adcock¹, E. M. Hausrath¹ and P. M. Forster²

¹Department of Geoscience, University of Nevada Las Vegas, 4505 S. Maryland Pkwy., Las Vegas, Nevada 89154, USA
²Department of Chemistry, University of Nevada Las Vegas, 4505 S. Maryland Pkwy., Las Vegas, Nevada 89154, USA

We currently seek a copyright agreement with Nature Geoscience to display abstracts of their cosmochemistry related publications.

Reference
Adcock CT, Hausrath EM and Forster PM  (2013) Readily available phosphate from minerals in early aqueous environments on Mars. Nature Geoscience 6:824–827.
[doi:10.1038/ngeo1923]

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Arkaprabha Sarangi and Isabelle Cherchneff

We study the formation of molecules and dust clusters in the ejecta of solar metallicity, Type II-P supernovae (SNe) using a chemical kinetic approach. We follow the evolution of molecules and small dust cluster masses from day 100 to day 1500 after explosion. We consider stellar progenitors with initial masses of 12, 15, 19, and 25 M_☉ that explode as SNe with stratified ejecta. The molecular precursors to dust grains comprise molecular chains, rings and small clusters of silica, silicates, metal oxides, sulfides and carbides, pure metals, and carbon, where the nucleation of silicate clusters is described by a two-step process of metal and oxygen addition. We study the impact of the ⁵⁶Ni mass on the type and amount of synthesized dust. We predict that large masses of molecules including CO, SiO, SiS, O₂, and SO form in the ejecta. We show that the discrepancy between the small dust masses detected at infrared wavelengths some 500 days post-explosion and the larger amounts of dust recently detected with Herschel in SN remnants can be explained by the non-equilibrium chemistry linked to the formation of molecules and dust clusters in the ejected material. Dust gradually builds up from small (~10−5 M_☉) to large masses (~5 × 10−2 M_☉) over a 5 yr period after explosion. Subsequent dust formation and/or growth is hampered by the shortage of chemical agents participating in the dust nucleation and the long timescale for accretion. The results highlight the dependence of the dust chemical composition and mass on the amount of ⁵⁶Ni synthesized during the explosion. This dependence may partly explain the diversity of epochs at which dust forms in SNe. More generally, our results indicate that Type II-P SNe are efficient but moderate dust producers with an upper limit on the mass of synthesized dust ranging from ~0.03 to 0.09 M_☉. Other dust sources must then operate at high redshift to explain the large quantities of dust present in young galaxies in the early universe.

Reference
Sarangi A and Cherchneff I (in press) The Chemically Controlled Synthesis of Dust in Type II-P Supernovae. The Astrophysical Journal
[doi:10.1088/0004-637X/776/2/107]

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A. Pommerol^1,*, N. Thomas¹, B. Jost¹, P. Beck², C. Okubo³, A. S. McEwen⁴

¹Physikalisches Institut, Universität Bern, Bern, Switzerland
²Institut de Planétologie et d’Astrophysique de Grenoble, UMR 5274, CNRS/Université Grenoble I, Grenoble, France
³U.S. Geological Survey, Astrogeology Research Center Survey, Flagstaff, Arizona, USA
⁴Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA

We have measured the bidirectional reflectance of analogs of dry, wet, and frozen Martian soils over a wide range of phase angles in the visible spectral range. All samples were produced from two geologic samples: the standard JSC Mars-1 soil simulant and Hawaiian basaltic sand. In a first step, experiments were conducted with the dry samples to investigate the effects of surface texture. Comparisons with results independently obtained by different teams with similar samples showed a satisfying reproducibility of the photometric measurements as well as a noticeable influence of surface textures resulting from different sample preparation procedures. In a second step, water was introduced to produce wet and frozen samples and their photometry investigated. Optical microscope images of the samples provided information about their microtexture. Liquid water, even in relatively low amount, resulted in the disappearance of the backscattering peak and the appearance of a forward-scattering peak whose intensity increases with the amount of water. Specular reflections only appeared when water was present in an amount large enough to allow water to form a film at the surface of the sample. Icy samples showed a wide variability of photometric properties depending on the physical properties of the water ice. We discuss the implications of these measurements in terms of the expected photometric behavior of the Martian surface, from equatorial to circum-polar regions. In particular, we propose some simple photometric criteria to improve the identification of wet and/or icy soils from multiple observations under different geometries.

Reference
Pommerol A, Thomas N, Jost B, Beck P, Okubo C and McEwen AS (in press) Photometric properties of Mars soils analogs. Journal of Geophysical Research – Planets, 118
[doi:10.1002/jgre.20158]
Published by arrangement with John Wiley & Sons

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C. P. Haynes¹ and C. Millet²

¹UMR 7600, CNRS/Université Pierre et Marie Curie, Paris, France
²CEA, DAM, DIF, Arpajon, France

We perform a multicomponent sensitivity analysis of how the physical and dynamical parameters that characterize a meteor (in-fall) affect the ground overpressure and period of a plausible emitted N-wave signal. The nonlinear propagation model used throughout is based upon Whitham’s nonlinearization method which is modified to take into account a stratified atmosphere. We use sensitivity indices, derived using a Fourier Amplitude Sensitivity Test, to measure how the meteor parameters’ uncertainties affect the uncertainty in the overpressure and period of an emitted N-wave. The investigated parameters include the azimuth, entry angle, diameter, drag coefficient, density, and initial velocity of the meteor, as well as the atmosphere. The method is used to re-examine the crater-forming meteorite fall near Carancas, Peru (2007). We obtain good agreement between the simulated signals and observed waveforms. It is shown that ground overpressure uncertainty depends on the atmospheric uncertainties that are strongly correlated with the unknown trajectory, whereas the period is governed by the diameter uncertainties. Finally, we consider new waveform parameters that help characterize the meteor.

Reference
Haynes CP and Millet C (in press) A sensitivity analysis of meteoric infrasound. Journal of Geophysical Research – Planets, 118
[doi:10.1002/jgre.20116]
Published by arrangement with John Wiley & Sons

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