Rita K. Mann¹, James Di Francesco^1,2, Doug Johnstone^1,2,3, Sean M. Andrews⁴, Jonathan P. Williams⁵, John Bally⁶, Luca Ricci⁷, A. Meredith Hughes⁸, and Brenda C. Matthews^1,2

¹National Research Council Canada, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
²Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada
³Joint Astronomy Centre, 660 North A’ohoku Place, University Park, Hilo, HI 96720, USA
⁴Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁵Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 USA
⁶CASA, University of Colorado, CB 389, Boulder, CO 80309, USA
⁷Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA
⁸Van Vleck Observatory, Astronomy Department, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459, USA

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of protoplanetary disks (“proplyds”) in the Orion Nebula Cluster. We imaged five individual fields at 856 μm containing 22 Hubble Space Telescope (HST)-identified proplyds and detected 21 of them. Eight of those disks were detected for the first time at submillimeter wavelengths, including the most prominent, well-known proplyd in the entire Orion Nebula, 114-426. Thermal dust emission in excess of any free-free component was measured in all but one of the detected disks, and ranged between 1 and 163 mJy, with resulting disk masses of 0.3-79 M _jup. An additional 26 stars with no prior evidence of associated disks in HST observations were also imaged within the 5 fields, but only 2 were detected. The disk mass upper limits for the undetected targets, which include OB stars, θ¹ Ori C, and θ¹ Ori F, range from 0.1 to 0.6 M _jup. Combining these ALMA data with previous Submillimeter Array observations, we find a lack of massive (3 M _jup) disks in the extreme-UV-dominated region of Orion, within 0.03 pc of θ¹ Ori C. At larger separations from θ¹ Ori C, in the far-UV-dominated region, there is a wide range of disk masses, similar to what is found in low-mass star forming regions. Taken together, these results suggest that a rapid dissipation of disk masses likely inhibits potential planet formation in the extreme-UV-dominated regions of OB associations, but leaves disks in the far-UV-dominated regions relatively unaffected.

Reference
Mann RK, Di Francesco J, Johnstone D, Andrews SM, Williams JP, Bally J, Ricci L, Hughes AM and Matthews BC (2014) ALMA Observations of the Orion Proplyds. The Astrophysical Journal 784:82
[doi:10.1088/0004-637X/784/1/82]

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T. Albertsson, D. Semenov, and Th. Henning

Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany

Formation and evolution of water in the solar system and the origin of water on Earth constitute one of the most interesting questions in astronomy. The prevailing hypothesis for the origin of water on Earth is by delivery through water-rich small solar system bodies. In this paper, the isotopic and chemical evolution of water during the early history of the solar nebula, before the onset of planetesimal formation, is studied. A gas-grain chemical model that includes multiply deuterated species and nuclear spin-states is combined with a steady-state solar nebula model. To calculate initial abundances, we simulated 1 Myr of evolution of a cold and dark TMC-1-like prestellar core. Two time-dependent chemical models of the solar nebula are calculated over 1 Myr: (1) a laminar model and (2) a model with two-dimensional (2D) turbulent mixing. We find that the radial outward increase of the H2O D/H ratio is shallower in the chemodynamical nebular model than in the laminar model. This is related to more efficient defractionation of HDO via rapid gas-phase processes because the 2D mixing model allows the water ice to be transported either inward and thermally evaporated or upward and photodesorbed. The laminar model shows the Earth water D/H ratio at r  2.5 AU, whereas for the 2D chemodynamical model this zone is larger, r  9 AU. Similarly, the water D/H ratios representative of the Oort-family comets, ~2.5-10 × 10^–4, are achieved within ~2-6 AU and ~2-20 AU in the laminar and the 2D model, respectively. We find that with regards to the water isotopic composition and the origin of the comets, the mixing model seems to be favored over the laminar model.

Reference
Albertsson T, Semenov D and Henning Th (2014) Chemodynamical Deuterium Fractionation in the Early Solar Nebula: The Origin of Water on Earth and in Asteroids and Comets. The Astrophysical Journal 784:39
[doi:10.1088/0004-637X/784/1/39]

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Derek W. Sears¹ and Robert Beauford²

¹Bay Area Environmental Research Institute/NASA Ames Research Center, Mountain View, California, USA
²Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, Arkansas, USA

A piece of the Sutter’s Mill meteorite, fragment SM2-1d, has been examined using thermoluminescence techniques to better understand its thermal and metamorphic history. The sample had very weak but easily measureable natural and induced thermoluminescence (TL) signals; the signal-to-noise ratio was better than 10. The natural TL was restricted to the high-temperature regions of the glow curve suggesting that the meteorite had been heated to approximately 300 °C within the time it takes for the TL signal to recover from a heating event, probably within the last 10⁵ years. It is possible that this reflects heating during release from the parent body, close passage by the Sun, or heating during atmospheric passage. Of these three options, the least likely is the first, but the other possibilities are equally likely. It seems that temperatures of approximately 300 °C reached 5 or 6 mm into the meteorite, so that all but one of the small Sutter’s Mill stones have been heated. The Dhajala normalized induced TL signal for SM2-1d is comparable to that of type 3.0 chondrites and is unlike normal CM chondrites, the class it most closely resembles, which do not have detectable TL sensitivity. The shape of the induced TL curve is comparable to other low-type ordinary, CV, and CO chondrites, in that it has a broad hummocky structure, but does not resemble any of them in detail. This suggests that Sutter’s Mill is a unique, low-petrographic–type (3.0) chondrite.

Reference
Sears DW and Beauford R (in press) The Sutter’s Mill meteorite: Thermoluminescence data on thermal and metamorphic history. Meteoritics & Planetary Science
[doi:10.1111/maps.12259]
Published by arrangement with John Wiley & Sons

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Anthony L. Piro¹ and Ehud Nakar²

¹Theoretical Astrophysics, California Institute of Technology, 1200 E California Boulevard, M/C 350-17, Pasadena, CA 91125, USA
²Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel

Ongoing transient surveys are presenting an unprecedented account of the rising light curves of Type Ia supernovae (SNe Ia). This early emission probes the shallowest layers of the exploding white dwarf (WD), which can provide constraints on the progenitor star and the properties of the explosive burning. We use semianalytic models of radioactively powered rising light curves to analyze these observations. As we have summarized in previous work, the main limiting factor in determining the surface distribution of ⁵⁶Ni is the lack of an unambiguously identified time of explosion, as would be provided by detection of shock breakout or shock-heated cooling. Without this the SN may in principle exhibit a “dark phase” for a few hours to days, where the only emission is from shock-heated cooling that is too dim to be detected. We show that by assuming a theoretically motivated time-dependent velocity evolution, the explosion time can be better constrained, albeit with potential systematic uncertainties. This technique is used to infer the surface ⁵⁶Ni distributions of three recent SNe Ia that were caught especially early in their rise. In all three we find fairly similar ⁵⁶Ni distributions. Observations of SN 2011fe and SN 2012cg probe shallower depths than SN 2009ig, and in these two cases ⁵⁶Ni is present merely ~10^-2 M_☉ from the WDs’ surfaces. The uncertainty in this result is up to an order of magnitude given the difficulty of precisely constraining the explosion time. We also use our conclusions about the explosion times to reassess radius constraints for the progenitor of SN 2011fe, as well as discuss the roughly t 2 power law that is inferred for many observed rising light curves.

Reference
Piro AL and Nakar E (2014) Constraints on Shallow 56Ni from the Early Light Curves of Type Ia Supernovae. The Astrophysical Journal 784:85
[doi:10.1088/0004-637X/784/1/85]

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Fred J. Ciesla

Department of the Geophysical Sciences, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA

Understanding the phases of water ice that were present in the solar nebula has implications for understanding cometary and planetary compositions as well as the internal evolution of these bodies. Here we show that amorphous ice formed more readily than previously recognized, with formation at temperatures <70 K being possible under protoplanetary disk conditions. We further argue that photodesorption and freeze-out of water molecules near the surface layers of the solar nebula would have provided the conditions needed for amorphous ice to form. This processing would be a natural consequence of ice dynamics and would allow for the trapping of noble gases and other volatiles in water ice in the outer solar nebula.

Reference
Ciesla FJ (2014) The Phases of Water Ice in the Solar Nebula. The Astrophysical Journal Letters 784:L1
[doi:10.1088/2041-8205/784/1/L1]

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David Jewitt^1,2, Jessica Agarwal³, Jing Li³, Harold Weaver⁴, Max Mutchler⁵, and Stephen Larson⁶

¹Department of Earth, Planetary and Space Sciences, UCLA, 595 Charles Young Drive East, Los Angeles, CA 90095-1567, USA
²Department of Physics and Astronomy, University of California at Los Angeles, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547, USA
³Max Planck Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau, Germany
⁴The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA
⁵Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁶Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Boulevard, Tucson, AZ 85721-0092, USA

Splitting of the nuclei of comets into multiple components has been frequently observed but, to date, no main-belt asteroid has been observed to break up. Using the Hubble Space Telescope, we find that main-belt asteroid P/2013 R3 consists of 10 or more distinct components, the largest up to 200 m in radius (assumed geometric albedo of 0.05) each of which produces a coma and comet-like dust tail. A diffuse debris cloud with total mass ~2 × 10⁸ kg further envelopes the entire system. The velocity dispersion among the components, ΔV ~ 0.2-0.5 m s^–1, is comparable to the gravitational escape speeds of the largest members, while their extrapolated plane-of-sky motions suggest a break up between 2013 February and September. The broadband optical colors are those of a C-type asteroid. We find no spectral evidence for gaseous emission, placing model-dependent upper limits to the water production rate ≤1 kg s^–1. Breakup may be due to a rotationally induced structural failure of the precursor body.

Reference
Jewitt D, Agarwal J, Li J, Weaver H, Mutchler M and Larson S (2014) Disintegrating Asteroid P/2013 R3. The Astrophysical Journal Letters 784:L8
[doi:10.1088/2041-8205/784/1/L8]

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J. R. Lyons†

Department of Earth & Space Sciences, UCLA, Los Angeles, California, USA
^†School of Earth & Space Exploration, Arizona State University, Tempe, Arizona, USA

CO photodissociation in the solar nebula and/or parent cloud has been proposed to be the mechanism responsible for forming the ¹⁶O-poor reservoir of the calcium-aluminum-rich inclusion (CAI) mixing line. However, laboratory experiments on CO photolysis found a wavelength dependence in the oxygen isotope ratios of the product O atoms, which was interpreted as proof that CO photolysis was not a viable mechanism. Here, I report photochemical simulations of these experiments using line-by-line CO spectra to identify the origin of the wavelength dependence. At long wavelengths (>105 nm), the line-by-line spectra for isotopic CO can explain the experimental data with a combination of C¹⁶O self-shielding and reduced dissociation probabilities for C¹⁸O. At short wavelengths, the greater number of diffuse bands increases the importance of mass-dependent fractionation, lowering the slope to below unity. The line-by-line isotopic spectra are then applied to CO photodissociation in a model solar nebula. Three FUV sources are considered (1) HD 303308, an O4 star in Carina; (2) HD 36981, a B5 star in Orion; and (3) TW Hydrae, a T Tauri star of 10 Myr age. Using reduced dissociation probabilities for C¹⁸O based on the photolysis experiments yields nebular water slopes approximately 0.95–1.0 for HD 303308 and TW Hya, and approximately 0.8–1.5 for HD 36981. For the central protostar case (TW Hya) with a simplified treatment of the 2-D radiative transfer, slopes approximately 0.95–1.0 are obtained, independent of the C¹⁸O dissociation probability. Greatly improved measurements of the C¹⁷O and C¹⁸O cross sections and dissociation probabilities are in progress.

Reference
Lyons JR (in press) Photodissociation of CO isotopologues: Models of laboratory experiments and implications for the solar nebula. Meteoritics & Planetary Science
[doi:10.1111/maps.12246]
Published by arrangement with John Wiley & Sons

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Marc Fries¹, Lucille Le Corre², Mike Hankey³, Jeff Fries⁴, Robert Matson⁵, Jake Schaefer⁶, Vishnu Reddy⁷

¹NASA Astromaterials Research and Exploration Science (ARES), Mail Code KT, Johnson Space Center, Houston, Texas, USA
²Planetary Science Institute, Tucson, Arizona, USA
³American Meteor Society, Monkton, Maryland, USA
⁴First Weather Group, Air Force Weather Agency, Offutt AFB, Nebraska, USA
⁵Science Applications International Corp., Seal Beach, California, USA
⁶NASA Dryden, Edwards, California, USA
⁷Planetary Science Institute, Tucson, Arizona, USA

The Sutter’s Mill C-type meteorite fall occurred on 22 April 2012 in and around the town of Coloma, California. The exact location of the meteorite fall was determined within hours of the event using a combination of eyewitness reports, weather radar imagery, and seismometry data. Recovery of the first meteorites occurred within 2 days and continued for months afterward. The recovery effort included local citizens, scientists, and meteorite hunters, and featured coordination efforts by local scientific institutions. Scientific analysis of the collected meteorites revealed characteristics that were available for study only because the rapid collection of samples had minimized terrestrial contamination/alteration. This combination of factors—rapid and accurate location of the event, participation in the meteorite search by the public, and coordinated scientific investigation of recovered samples—is a model that was widely beneficial and should be emulated in future meteorite falls. The tools necessary to recreate the Sutter’s Mill recovery are available, but are currently underutilized in much of the world. Weather radar networks, scientific institutions with interest in meteoritics, and the interested public are available globally. Therefore, it is possible to repeat the Sutter’s Mill recovery model for future meteorite falls around the world, each for relatively little cost with a dedicated researcher. Doing so will significantly increase the number of fresh meteorite falls available for study, provide meteorite material that can serve as the nuclei of new meteorite collections, and will improve the public visibility of meteoritics research.

Reference
Fries M, Le Corre L, Hankey M, Fries J, Matson R, Schaefer J and Reddy V (in press) Detection and rapid recovery of the Sutter’s Mill meteorite fall as a model for future recoveries worldwide. Meteoritics & Planetary Science
[doi:10.1111/maps.12249]
Published by arrangement with John Wiley & Sons

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J. Ormö¹, E. Sturkell², J. Nõlvak³, I. Melero-Asensio¹, Å. Frisk^4,†, T. Wikström⁵

¹Centro de Astrobiologia (INTA-CSIC), Madrid, Spain
²Department of Earth Sciences, University of Gothenburg, Sweden, Gothenburg, Sweden
³Institute of Geology, Tallinn University of Technology, Tallinn, Estonia
⁴Paläontologisches Institut und Museum, Universität Zürich, Zürich, Switzerland
⁵Stockholm, Sweden
^†Palaeobiology, Department of Earth Sciences, Uppsala University, Uppsala, Sweden

The Målingen structure is an approximately 700 m wide, rimmed, sediment-filled, circular depression in Precambrian crystalline basement approximately 16.2 km from the concentric, marine-target Lockne crater (inner, basement crater diameter approximately 7.5 km, total diameter in sedimentary strata approximately 13.5 km). We present here results from geologic mapping, a 148.8 m deep core drilling from the center of the structure, detailed biostratigraphic dating of the structure’s formation and its age correlation with Lockne, chemostratigraphy of the sedimentary infill, and indication for shock metamorphism in quartz from breccias below the crater infill. The drill core reveals, from bottom to the top, approximately 33 m of basement rocks with increased fracturing upward, approximately 10 m of polymict crystalline breccia with shock features, approximately 97 m of slumped Cambrian mudstone, approximately 4.7 m of a normally graded, polymict sedimentary breccia that in its uppermost part grades into sandstone and siltstone (cf. resurge deposits), and approximately 1.6 m of secular sediments. The combined data set shows that the Målingen structure formed in conjunction with the Lockne crater in the same marine setting. The shape and depth of the basement crater and the cored sequence of crystalline breccias with shocked quartz, slumped sediments, and resurge deposits support an impact origin. The stratigraphic and geographic relationship with Lockne suggests the Lockne and Målingen craters to be the first described doublet impact structure by a binary asteroid into a marine-target setting.

Reference
Ormö J, Sturkell E, Nõlvak J, Melero-Asensio I, Frisk Å and Wikström T (in press) The geology of the Målingen structure: A probable doublet to the Lockne marine-target impact crater, central Sweden. Meteoritics & Planetary Science
[doi:10.1111/maps.12251]
Published by arrangement with John Wiley & Sons

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M. Kimura^1,5, J. A. Barrat², M. K. Weisberg^3,4, N. Imae⁵, A. Yamaguchi⁵, H. Kojima⁵

¹Faculty of Science, Ibaraki University, Mito, Japan
²Université Européenne de Bretagne, 2CNRS UMR 6538 (Domaines Océaniques), U.B.O.-I.U.E.M., Plouzané Cedex, France
³Department of Physical Sciences, Kingsborough College and Graduate School of the City University of New York, Brooklyn, New York, USA
⁴Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
⁵National Institute of Polar Research, Tokyo, Japan

Carbonaceous chondrites are classified into several groups. However, some are ungrouped. We studied one such ungrouped chondrite, Y-82094, previously classified as a CO. In this chondrite, chondrules occupy 78 vol%, and the matrix is distinctly poor in abundance (11 vol%), compared with CO and other C chondrites. The average chondrule size is 0.33 mm, different from that in C chondrites. Although these features are similar to those in ordinary chondrites, Y-82094 contains 3 vol% Ca-Al-rich inclusions and 5% amoeboid olivine aggregates (AOAs). Also, the bulk composition resembles that of CO chondrites, except for the volatile elements, which are highly depleted. The oxygen isotopic composition of Y-82094 is within the range of CO and CV chondrites. Therefore, Y-82094 is an ungrouped C chondrite, not similar to any other C chondrite previously reported. Thin FeO-rich rims on AOA olivine and the mode of occurrence of Ni-rich metal in the chondrules indicate that Y-82094 is petrologic type 3.2. The extremely low abundance of type II chondrules and high abundance of Fe-Ni metal in the chondrules suggest reducing condition during chondrule formation. The depletion of volatile elements indicates that the components formed under high-temperature conditions, and accreted to the parent body of Y-82094. Our study suggests a wider range of formation conditions than currently recorded by the major C chondrite groups. Additionally, Y-82094 may represent a new, previously unsampled, asteroidal body.

Reference
Kimura M, Barrat JA, Weisberg MK, Imae N, Yamaguchi A and Kojima H (in press) Petrology and bulk chemistry of Yamato-82094, a new type of carbonaceous chondrite. Meteoritics & Planetary Science
[doi:10.1111/maps.12254]
Published by arrangement with John Wiley & Sons

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