Yada T et al.¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Lunar and Planetary Exploration Program Group, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan

The Planetary Material Sample Curation Facility of JAXA (PMSCF/JAXA) was established in Sagamihara, Kanagawa, Japan, to curate planetary material samples returned from space in conditions of minimum terrestrial contaminants. The performances for the curation of Hayabusa-returned samples had been checked with a series of comprehensive tests and rehearsals. After the Hayabusa spacecraft had accomplished a round-trip flight to asteroid 25143 Itokawa and returned its reentry capsule to the Earth in June 2010, the reentry capsule was brought back to the PMSCF/JAXA and was put to a series of processes to extract recovered samples from Itokawa. The particles recovered from the sample catcher were analyzed by electron microscope, given their ID, grouped into four categories, and preserved in dimples on quartz slide glasses. Some fraction of them has been distributed for initial analyses at NASA, and will be distributed for international announcement of opportunity (AO), but a certain fraction of them will be preserved in vacuum for future analyses.

Reference
Yada T et al. (2014) Hayabusa-returned sample curation in the Planetary Material Sample Curation Facility of JAXA. Meteoritics & Planetary Science 49:135–153.
[doi:10.1111/maps.12027]
Published by arrangement with John Wiley & Sons

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Elmer J. W., Evans C. L., Embree J. J., Gallegos G. F. and Summers L. T.

Materials Engineering Division, Lawrence Livermore National Laboratory, Livermore, CA, USA

We do not have a copyright agreement with this unusual journal for cosmochemistry.

Reference
Elmer JW, Evans CL, Embree JJ, Gallegos GF and Summers LT (2014) Electron beam weldability of a group IAB iron meteorite. Science and Technology of Welding and Joining
[doi:10.1179/1362171813Y.0000000188]

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D. Harsono^1,2, J. K. Jørgensen^3,4, E. F. van Dishoeck^1,5, M. R. Hogerheijde¹, S. Bruderer⁵, M. V. Persson^1,3,4 and J. C. Mottram¹

¹Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden The Netherlands
²SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
³Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
⁴Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, 1350 Copenhagen K, Denmark
⁵Max-Planck-Institut für extraterretrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany

Context. Disks are observed around pre-main sequence stars, but how and when they form is still heavily debated. While disks around young stellar objects have been identified through thermal dust emission, spatially and spectrally resolved molecular line observations are needed to determine their nature. Only a handful of embedded rotationally supported disks have been identified to date.
Aims. We identify and characterize rotationally supported disks near the end of the main accretion phase of low-mass protostars by comparing their gas and dust structures.
Methods. Subarcsecond observations of dust and gas toward four Class I low-mass young stellar objects in Taurus are presented at significantly higher sensitivity than previous studies. The ¹³CO and C¹⁸O J = 2–1 transitions at 220 GHz were observed with the Plateau de Bure Interferometer at a spatial resolution of ≤0.8″ (56 AU radius at 140 pc) and analyzed using uv-space position velocity diagrams to determine the nature of their observed velocity gradient.
Results. Rotationally supported disks (RSDs) are detected around 3 of the 4 Class I sources studied. The derived masses identify them as Stage I objects; i.e., their stellar mass is higher than their envelope and disk masses. The outer radii of the Keplerian disks toward our sample of Class I sources are ≤100 AU. The lack of on-source C¹⁸O emission for TMR1 puts an upper limit of 50 AU on its size. Flattened structures at radii >100 AU around these sources are dominated by infalling motion (υ ∝ r^-1). A large-scale envelope model is required to estimate the basic parameters of the flattened structure from spatially resolved continuum data. Similarities and differences between the gas and dust disk are discussed. Combined with literature data, the sizes of the RSDs around Class I objects are best described with evolutionary models with an initial rotation of Ω = 10^-14 Hz and slow sound speeds. Based on the comparison of gas and dust disk masses, little CO is frozen out within 100 AU in these disks.
Conclusions. Rotationally supported disks with radii up to 100 AU are present around Class I embedded objects. Larger surveys of both Class 0 and I objects are needed to determine whether most disks form late or early in the embedded phase.

Reference
Harsono D, Jørgensen JK, van Dishoeck EF, Hogerheijde MR, Bruderer S, Persson MV and Mottram JC (2014) Rotationally-supported disks around Class I sources in Taurus: disk formation constraints. Astronomy & Astrophysics A562:A77.
[doi:10.1051/0004-6361/201322646]
Reproduced with permission © ESO

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S. Fornasier^a,b, C. Lantz^a,b, M.A. Barucci^a, M. Lazzarin^c

^aLESIA, Observatoire de Paris, CNRS, UPMC Univ Paris 06, Univ. Paris Diderot, 5 Place J. Janssen, 92195 Meudon Pricipal Cedex, France
^bUniv. Paris Diderot, Sorbonne Paris Cité, 4 rue Elsa Morante, 75205 Paris Cedex 13
^cDepartment of Physics and Astronomy of the University of Padova, Via Marzolo 8 35131 Padova, Italy

This work focuses on the study of the aqueous alteration process which acted in the main belt and produced hydrated minerals on the altered asteroids. Hydrated minerals have been found mainly on Mars surface, on main belt primitive asteroids and possibly also on few TNOs. These materials have been produced by hydration of pristine anhydrous silicates during the aqueous alteration process, that, to be active, needed the presence of liquid water under low temperature conditions (below 320 K) to chemically alter the minerals. The aqueous alteration is particularly important for unraveling the processes occurring during the earliest times of the Solar System history, as it can give information both on the asteroids thermal evolution and on the localization of water sources in the asteroid belt.
To investigate this process, we present reflected light spectral observations in the visible region (0.4–0.94 μm) of 80 asteroids belonging to the primitive classes C (prevalently), G, F, B and P, following the Tholen (1984) classification scheme. We find that about 65 % of the C-type and all the G-type asteroids investigated reveal features suggesting the presence of hydrous materials, mainly a band centered around 0.7 μm, while we do not find evidence of hydrated materials in the other low albedo asteroids (B, F, and P) investigated.
We combine the present observations with the visible spectra of asteroids available in the literature for a total of 600 primitive main belt asteroids. We analyze all these spectra in a similar way to characterize the absorption band parameters (band center, depth and width) and spectral slope, and to look for possible correlations between the aqueous alteration process and the asteroids taxonomic classes, orbital elements, heliocentric distances, albedo and sizes. Our analysis shows that the aqueous alteration sequence starts from the P-type objects, practically unaltered, and increases through the P → F → B → C → G asteroids, these last being widely aqueous altered, strengthening thus the results previously obtained by Vilas (1994). Around 50% of the observed C-type asteroids show absorption feature in the visible range due to hydrated silicates, implying that more than ~70% of them will have a 3 μm absorption band and thus hydrated minerals on their surfaces, based on correlations between those two absorptions (Howell et al., 2011).
We find that the aqueous alteration process dominates in primitive asteroids located between 2.3 and 3.1 AU, that is at smaller heliocentric distances than previously suggested by Vilas et al. (1993). The percentage of hydrated asteroids is strongly correlated with their size. The aqueous alteration process is less effective for bodies smaller than 50 km, while it dominates in the 50–240 km sized primitive asteroids.
No correlation is found between the aqueous alteration process and the asteroids albedo or orbital elements. Comparing the ~0.7 μm band parameters of hydrated silicates and CM2 carbonaceous chondrites, the meteorites that have aqueous altered asteroids as parent bodies, we see that the band center of meteorites is at longer wavelengths than that of asteroids. This difference on center positions may be attributed to different minerals abundances, and to the fact that CM2 available on Earth might not be representative of the whole aqueous altered asteroids population.

Reference
Fornasier S, Lantz C, Barucci MA and Lazzarin M (in press) Aqueous alteration on main belt primitive asteroids: results from visible spectroscopy. Icarus
[doi:10.1016/j.icarus.2014.01.040]
Copyright Elsevier

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F. Nimmo^a and J.R. Spencer^b

^aDept. Earth and Planetary Sciences, University of California, Santa Cruz, 1156 High St., Santa Cruz, CA 95064, USA
^bSouthwest Research Institute, 1050 Walnut St. Suite 300, Boulder CO 80302, USA

We investigate the origins of Triton’s deformed and young surface. Assuming Triton was captured early in solar system history, the bulk of the energy released during capture will have been lost, and cannot be responsible for its present-day activity. Radiogenic heating is sufficient to maintain a long-lived ocean beneath a conductive ice shell, but insufficient to cause convective deformation and yielding at the surface. However, Triton’s high inclination likely causes a significant (≈0.7°) obliquity, resulting in large heat fluxes due to tidal dissipation in any subsurface ocean. For a 300 km thick ice shell, the estimated ocean heat production rate (≈0.3 TW) is capable of producing surface yielding and mobile-lid convection. Requiring convection places an upper bound on the ice shell viscosity, while the requirement for yielding imposes a lower bound. Both bounds can be satisfied with an ocean temperature ≈240 K for our nominal temperature-viscosity relationship, suggesting the presence of an antifreeze such as NH₃. In our view, Triton’s geological activity is driven by obliquity tides, which arise because of its inclination. In contrast, Pluto is unlikely to be experiencing significant tidal heating. While Pluto may have experienced ancient tectonic deformation, we do not anticipate seeing the kind of young, deformed surfaces seen at Triton.

Reference
Nimmo F and Spencer JR (in press) Powering Triton’s recent geological activity by obliquity tides: Implications for Pluto geology. Icarus
[doi:10.1016/j.icarus.2014.01.044]
Copyright Elsevier

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Devin L. Schrader^1,a, Kazuhide Nagashima^a, Alexander N. Krot^a, Ryan C. Ogliore^a and Eric Hellebrand^b

^aHawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
^bDepartment of Geology and Geophysics, School of Ocean, Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
¹Present Address: Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, PO Box 37012, MRC 119, Washington, D.C. 20013, USA

To better understand the environment of chondrule formation and constrain the O-isotope composition of the ambient gas in the Renazzo-like carbonaceous (CR) chondrite chondrule-forming region, we studied the mineralogy, petrology, and in situ O-isotope compositions of olivine in 11 barred olivine (BO) chondrules and pyroxene and silica in three type I porphyritic chondrules from the CR chondrites Gao-Guenie (b), Graves Nunataks (GRA) 95229, Pecora Escarpment (PCA) 91082, and Shişr 033. BO chondrules experienced a higher degree of melting than porphyritic chondrules, and therefore, it has been hypothesized that they more accurately recorded the O-isotope composition of the gas in chondrule-forming regions. We studied the O-isotope composition of silica as it has been hypothesized to have formed via direct condensation from the gas.
BO chondrules constitute ~4% of the total CR chondrule population by volume. On a three-isotope oxygen diagram (δ¹⁷O vs. δ¹⁸O), olivine phenocrysts in type I and type II BO chondrules plot along ~ slope-1 line; with the exception of a type II BO chondrule that plots along ~ slope-0.5 line. Olivine phenocrysts in type I and type II BO chondrules have similar but more restricted ranges of Δ¹⁷O values (~ -3.8 to ~ -1.3‰ and ~ -0.8 to ~ +1.4‰, respectively) than those in type I and type II porphyritic chondrules (~ -4.6 to ~ -0.3‰ and ~ -1.8 to ~ +0.9‰, respectively). The observation that olivine grains in type I BO chondrules have similar chemical and O-isotope compositions to those of olivine in their porphyritic counterparts argues against the hypothesis that olivine grains in type I porphyritic chondrules are xenocrysts and represent relict fragments of early formed planetesimals.
The compositional and O-isotope data suggest that BO chondrules experienced more extensive, but incomplete exchange with the ambient gas than porphyritic chondrules. We suggest that CR chondrules formed from relatively ¹⁶O-enriched solids in the presence of relatively ¹⁶O-depleted gaseous H₂O. The O-isotope compositions of chondrule olivine likely result from differences in the O-isotope composition of both the chondrule precursors and the ambient gas during chondrule formation. The inferred O-isotope composition of this gas (Δ¹⁷O ranges from ~ -3‰ to +3‰) is inconsistent with a high abundance of water from the outer Solar System, which has been predicted to be isotopically heavy.

Reference
Schrader DL, Nagashima K, Krot AN, Ogliore RC and Hellebrand E (in press) Variations in the O-isotope composition of gas during the formation of chondrules from the CR chondrites. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2014.01.034]
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Stefan T.M. Peters^a,b, Carsten Münker^a,b,1, Harry Becker^c,2, Toni Schulz^d,3

^aInstitut für Geologie und Mineralogie, Universität zu Köln, Zülpicherstr. 49b, 50674 Cologne, Germany
^bSteinmann-Institut, Poppelsdorfer Schloss, 53115 Bonn, Germany
^cInstitut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin, Germany
^dDepartment of Lithospheric Research, Universität Wien, Althanstrasse 14, A-1090, Vienna, Austria

The decay of the rare nuclide ¹⁸⁴Os by alpha emission to ¹⁸⁰W has been theoretically predicted, but was previously never observed in experiments. Variable excesses of ¹⁸⁰W were recently observed for iron meteorites, but the contribution to these excesses by ¹⁸⁴Os-decay was regarded as insignificant. Here, we present combined ¹⁸⁰W and Os–W concentration data for meteorites and terrestrial rocks, now indicating that the ¹⁸⁰W heterogeneities can be explained by α-decay of ¹⁸⁴Os. A combined ¹⁸⁴Os–¹⁸⁰W isochron for iron meteorites and chondrites yields a decay constant value of λ¹⁸⁴Os(α) of 6.49±1.34×10⁻¹⁴ a⁻¹ (half life 1.12±0.23×10¹³ yr), in good agreement with theoretical estimates. The ¹⁸⁴Os–¹⁸⁰W decay system may constitute a viable tracer and chronometer for important geological processes like core formation, silicate differentiation or late accretion processes. This is illustrated by a measured ¹⁸⁰W-deficit in terrestrial basalts relative to chondrites by 1.16±0.69 parts in 10 000, consistent with core formation ~4.5 Ga ago.

Reference
Peters STM, Münker C, Becker H and Schulz T (2014) Alpha-decay of 184Os revealed by radiogenic 180W in meteorites: Half life determination and viability as geochronometer. Earth and Planetary Science Letters 391:69–76.
[doi:10.1016/j.epsl.2014.01.030]
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Liping Jin1 and Min Li

College of Physics, Jilin University, Changchun, Jilin 130012, China

We show that the diversity of extrasolar planetary systems may be related to the diversity of molecular cloud cores. In previous studies of planet formation, artificial initial conditions of protoplanetary disks or steady state disks, such as the minimum mass nebula model, have often been used so that the influence of cloud core properties on planet formation is not realized. To specifically and quantitatively demonstrate our point, we calculate the dependence of disk properties on cloud core properties and show that the boundary of the giant planet formation region in a disk is a function of cloud core properties with the conventional core accretion model of giant planet formation. The gravitational stability of a disk depends on the properties of its progenitor cloud core. We also compare our calculations with observations of extrasolar planets. From the observational data of cloud cores, our model could infer the range and most frequent values of observed semimajor axes of extrasolar planets. Our calculations suggest that planet formation at the snowline alone could not completely explain the semimajor axis distribution. If the current observations are not biased, our calculations indicate that the planet formation at the snowline is inefficient. We suggest that there will be more observed planets with semimajor axis <9 AU than >9 AU, even with a longer duration of observations, if the planet formation at the snowline is inefficient.

Reference
Jin L and Li M (2014) Diversity of Extrasolar Planets and Diversity of Molecular Cloud Cores. I. Semimajor Axes. The Astrophysical Journal 783:37.
[doi:10.1088/0004-637X/783/1/37]

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S. C. Lowry¹, P. R. Weissman², S. R. Duddy¹, B. Rozitis³, A. Fitzsimmons⁴, S. F. Green³, M. D. Hicks², C. Snodgrass⁵, S. D. Wolters³, S. R. Chesley², J. Pittichová² and P. van Oers⁶

¹Centre for Astrophysics and Planetary Science, School of Physical Sciences (SEPnet), The University of Kent, Canterbury, CT2 7NH, UK
²Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
³Planetary and Space Sciences, Department of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
⁴Astrophysics Research Centre, Queens University Belfast, Belfast, BT7 1NN, UK
⁵Max Planck Institute for Solar System Research, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
⁶Isaac Newton Group of Telescopes, 38700 Santa Cruz de la Palma, Canary Islands, Spain

Context. Near-Earth asteroid (25143) Itokawa was visited by the Hayabusa spacecraft in 2005, resulting in a highly detailed shape and surface topography model. This model has led to several predictions for the expected radiative torques on this asteroid, suggesting that its spin rate should be decelerating.
Aims. To detect changes in rotation rate that may be due to YORP-induced radiative torques, which in turn may be used to investigate the interior structure of the asteroid.
Methods. Through an observational survey spanning 2001 to 2013 we obtained rotational lightcurve data at various times over the last five close Earth-approaches of the asteroid. We applied a polyhedron-shape-modelling technique to assess the spin-state of the asteroid and its long term evolution. We also applied a detailed thermophysical analysis to the shape model determined from the Hayabusa spacecraft.
Results. We have successfully measured an acceleration in Itokawa’s spin rate of dω/dt = (3.54 ± 0.38) × 10^-8 rad day^-2, equivalent to a decrease of its rotation period of ~45 ms year^-1. From the thermophysical analysis we find that the centre-of-mass for Itokawa must be shifted by ~21 m along the long-axis of the asteroid to reconcile the observed YORP strength with theory.
Conclusions. This can be explained if Itokawa is composed of two separate bodies with very different bulk densities of 1750 ± 110 kg m^-3 and 2850 ± 500 kg m^-3, and was formed from the merger of two separate bodies, either in the aftermath of a catastrophic disruption of a larger differentiated body, or from the collapse of a binary system. We therefore demonstrate that an observational measurement of radiative torques, when combined with a detailed shape model, can provide insight into the interior structure of an asteroid. Futhermore, this is the first measurement of density inhomogeneity within an asteroidal body, that reveals significant internal structure variation. A specialised spacecraft is normally required for this.

Reference
Lowry SC, Weissman PR, Duddy SR, Rozitis B, Fitzsimmons A, Green SF, Hicks MD, Snodgrass C, Wolters SD, Chesley SR, Pittichová J and van Oers P (2014) The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up.  Astronomy & Astrophysics 562:A48.
[doi:10.1051/0004-6361/201322175]
Reproduced with permission © ESO

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J.E. Chambers

Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road, NW Washington DC 20015

In the core accretion model for giant planet formation, a solid core forms by coagulation of dust grains in a protoplanetary disk and then accretes gas from the disk when the core reaches a critical mass. Both stages must be completed in a few million years before the disk gas disperses. The slowest stage of this process may be oligarchic growth in which a giant-planet core grows by sweeping up smaller, asteroid-size planetesimals. Here, we describe new numerical simulations of oligarchic growth using a particle-in-a-box model. The simulations include several processes that can effect oligarchic growth: (i) planetesimal fragmentation due to mutual collisions, (ii) the modified capture rate of planetesimals due to a core’s atmosphere, (iii) drag with the disk gas during encounters with the core (so-called “pebble accretion”), (iv) modification of particle velocities by turbulence and drift caused by gas drag, (v) the presence of a population of mm-to-m size “pebbles” that represent the transition point between disruptive collisions between larger particles, and mergers between dust grains, and (vi) radial drift of small objects due to gas drag. Collisions between planetesimals rapidly generate a population of pebbles. The rate at which a core sweeps up pebbles is controlled by pebble accretion dynamics. Metre-size pebbles lose energy during an encounter with a core due to drag, and settle towards the core, greatly increasing the capture probability during a single encounter. Millimetre-size pebbles are tightly coupled to the gas and most are swept past the core during an encounter rather than being captured. Accretion efficiency per encounter increases with pebble size in this size range. However, radial drift rates also increase with size, so metre-size objects encounter a core on many fewer occasions than mm-size pebbles before they drift out of a region. The net result is that core growth rates vary weakly with pebble size, with the optimal diameter being about 10 cm. The main effect of planetesimal size is to determine the rate of mutual collisions, fragment production and the formation of pebbles. 1-km-diameter planetesimals collide frequently and have low impact strengths, leading to a large surface density of pebbles and rapid core growth via pebble accretion. 100-km-diameter planetesimals produce fewer pebbles, and pebble accretion plays a minor role in this case. The strength of turbulence in the gas determines the scale height of pebbles in the disk, which affects the rate at which they are accreted. For an initial solid surface density of 12 g/cm² at 5 AU, with10-cm diameter pebbles and a disk viscosity parameter α=10^-4, a 10-Earth mass core can form in 3 My for 1–10 km diameter planetesimals. The growth of such a core requires longer than 3 My if planetesimals are 100 km in diameter.

Reference
Chambers JE (in press) Giant Planet Formation with Pebble Accretion. Icarus
[doi:10.1016/j.icarus.2014.01.036]
Copyright Elsevier

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