Matija Ćuk^a, Brett J. Gladman^b, David Nesvorný^c

^aCarl Sagan Center, SETI Institute, 189 North Bernardo Avenue, Mountain View, CA 94043
^bDepartment of Physics and Astronomy, University of British Columbia 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
^cSouthwest Research Institute, 1050 Walnut St, Suite 400, Boulder, CO 80302

The Hungaria asteroids are interior to the main asteroid belt, with semimajor axes between 1.8 and 2 AU, low eccentricities and inclinations of 16-35 degrees. Small asteroids in the Hungaria region are dominated by a collisional family associated with (434) Hungaria. The dominant spectral type of the Hungaria group is the E or X-type (Warner et al., 2009), mostly due to the E-type composition of Hungaria and its genetic family. It is widely believed the E-type asteroids are related to the aubrite meteorites, also known as enstatite achondrites (Gaffey et al., 1992). Here we explore the hypothesis that aubrites originate in the Hungaria family. In order to test this connection, we compare model Cosmic Ray Exposure ages from orbital integrations of model meteoroids with those of aubrites. We show that long CRE ages of aubrites (longest among stony meteorite groups) reflect the delivery route of meteoroids from Hungarias to Earth being different than those from main-belt asteroids. We find that the meteoroids from Hungarias predominantly reach Earth by Yarkovsky-drifting across the orbit of Mars, with no assistance from orbital resonances. We conclude that the CRE ages of aubrites are fully consistent with a dominant source at the inner boundary of the Hungaria family at 1.7 AU. From here, meteoroids reach Earth through the Mars-crossing region, with relatively quick delivery times favored due to collisions (with Hungarias and the inner main-belt objects). We find that, after Vesta, (434) Hungaria is the best candidate for an asteroidal source of an achondrite group.

Reference
Ćuk MGladman BJ and Nesvorný D (in press) Hungaria Asteroid Family as the Source of Aubrite Meteorites. Icarus
[doi:10.1016/j.icarus.2014.05.048]
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Petr Pokorný¹, David Vokrouhlický¹, David Nesvorný², Margaret Campbell-Brown³ and Peter Brown³

¹Institute of Astronomy, Charles University, V Holešovičkách 2, CZ-18000 Prague 8, Czech Republic
²Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302, USA
³Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7, Canada

More than a decade of radar operations by the Canadian Meteor Orbit Radar have allowed both young and moderately old streams to be distinguished from the dispersed sporadic background component. The latter has been categorized according to broad radiant regions visible to Earth-based observers into three broad classes: the helion and anti-helion source, the north and south apex sources, and the north and south toroidal sources (and a related arc structure). The first two are populated mainly by dust released from Jupiter-family comets and new comets. Proper modeling of the toroidal sources has not to date been accomplished. Here, we develop a steady-state model for the toroidal source of the sporadic meteoroid complex, compare our model with the available radar measurements, and investigate a contribution of dust particles from our model to the whole population of sporadic meteoroids. We find that the long-term stable part of the toroidal particles is mainly fed by dust released by Halley type (long period) comets (HTCs). Our synthetic model reproduces most of the observed features of the toroidal particles, including the most troublesome low-eccentricity component, which is due to a combination of two effects: particles’ ability to decouple from Jupiter and circularize by the Poynting–Robertson effect, and large collision probability for orbits similar to that of the Earth. Our calibrated model also allows us to estimate the total mass of the HTC-released dust in space and check the flux necessary to maintain the cloud in a steady state.

Reference
Pokorný P, Vokrouhlický D, Nesvorný D, Campbell-Brown M and Brown P (2014) Dynamical model for the toroidal sporadic meteors. The Astrophysical Journal 789:25.
[doi:10.1088/0004-637X/789/1/25]

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Yves Marrocchi^1,2, Matthieu Gounelle^3,4, Ingrid Blanchard^3,5, Florent Caste^3,6 and Anton T. Kearsley⁷

¹Université de Lorraine, CRPG, UMR 7358, Vandoeuvre les Nancy, France
²CNRS, CRPG UMR 7358, Vandoeuvre les Nancy, France
³Laboratoire de Minéralogie et de Cosmochimie du Muséum, MNHN and CNRS, UMR 7202, Paris, France
⁴Institut Universitaire de France, Maison des Universités, Paris, France
⁵Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, Paris, France
⁶Institut de Minéralogie et de Physique des Milieux Condensés, UMR 7590, CNRS-UPMC, Paris, France
⁷Imaging and Analysis Centre, Department of Science Facilities, Natural History Museum, London, UK

We report a petrographic and mineralogical survey of Paris, a new CM chondrite considered to be the least-altered CM identified so far (Hewins et al. 2014). Compared to other CMs, Paris exhibits (1) a higher concentration of Fe-Ni metal beads, with nickel contents in the range 4.1–8.1 wt%; (2) the systematic presence of thin lamellae and tiny blebs of pentlandite in pyrrhotite grains; and (3) ubiquitous tochilinite/cronstedtite associations with higher FeO/SiO₂ and S/SiO₂ ratios. In addition, Paris shows the highest concentration of trapped ³⁶Ar reported so far for a CM chondrite (Hewins et al. 2014). In combination with the findings of previous studies, our data confirm the reliability of (1) the alteration sequence based on the chemical composition of tochilinite/cronstedtite associations to quantify the fluid alteration processes and (2) the use of Cr content variability in type II ferroan chondrule olivine as a proxy of thermal metamorphism. In contrast, the scales based on (1) the Fe³⁺ content of serpentine in the matrix to estimate the degree of aqueous alteration and (2) the chemical composition of Fe-Ni metal beads for quantifying the intensity of the thermal metamorphism are not supported by the characteristics of Paris. It also appears that the amount of trapped ³⁶Ar is a sensitive indicator of the secondary alteration modifications experienced by chondrites, for both aqueous alteration and thermal metamorphism. Considering Paris, our data suggest that this chondrite should be classified as type 2.7 as it suffered limited but significant fluid alteration and only mild thermal metamorphism. These results point out that two separated scales should be used to quantify the degree of the respective role of aqueous alteration and thermal metamorphism in establishing the characteristics of CM chondrites.

Reference
Marrocchi Y, Gounelle M, Blanchard I, Caste F and Kearsley AT (in press) The Paris CM chondrite: Secondary minerals and asteroidal processing. Meteoritics & Planetary Science
[doi:10.1111/maps.12329]
Published by arrangement with John Wiley & Sons

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Sterken, V. J¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Institut für Raumfahrtsysteme, University Stuttgart, Stuttgart, Germany

On the basis of an interstellar dust model compatible with Ulysses and Galileo observations, we calculate and predict the trajectories of interstellar dust (ISD) in the solar system and the distribution of the impact speeds, directions, and flux of ISD particles on the Stardust Interstellar Dust Collector during the two collection periods of the mission. We find that the expected impact velocities are generally low (<10 km s⁻¹) for particles with the ratio of the solar radiation pressure force to the solar gravitational force β > 1, and that some of the particles will impact on the cometary side of the collector. If we assume astronomical silicates for particle material and a density of 2 g cm⁻³, and use the Ulysses measurements and the ISD trajectory simulations, we conclude that the total number of (detectable) captured ISD particles may be on the order of 50. In companion papers in this volume, we report the discovery of three interstellar dust candidates in the Stardust aerogel tiles. The impact directions and speeds of these candidates are consistent with those calculated from our ISD propagation model, within the uncertainties of the model and of the observations.

Reference
Sterken et al. (in press) Stardust Interstellar Preliminary Examination X: Impact speeds and directions of interstellar grains on the Stardust dust collector. Meteoritics & Planetary Science
[doi:10.1111/maps.12219]
Published by arrangement with John Wiley & Sons

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Maurizio Gemelli, Massimo D’Orazio and Luigi Folco

Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy

We evaluate the performance of a hand-held XRF (HHXRF) spectrometer for the bulk analysis of iron meteorites. Analytical precision and accuracy were tested on metal alloy certified reference materials and iron meteorites of known chemical composition. With minimal sample preparation (i.e., flat or roughly polished surfaces) HHXRF allowed the precise and accurate determination of most elements heavier than Mg, with concentrations > 0.01% m/m in metal alloy CRMs, and of major elements Fe and Ni and minor elements Co, P and S (generally ranging from 0.1 to 1% m/m) in iron meteorites. In addition, multiple HHXRF spot analyses could be used to determine the bulk chemical composition of iron meteorites, which are often characterised by sulfide and phosphide accessory minerals. In particular, it was possible to estimate the P and S bulk contents, which are of critical importance for the petrogenesis and evolution of Fe-Ni-rich liquids and iron meteorites. This study thus validates HHXRF as a valuable tool for use in meteoritics, allowing the rapid, non-destructive (a) identification of the extraterrestrial origin of metallic objects (i.e., archaeological artefacts); (b) preliminary chemical classification of iron meteorites; (c) identification of mislabelled/unlabelled specimens in museums and private collections and (d) bulk analysis of iron meteorites.

Reference
Gemelli M, D’Orazio M and Folco L (in press) Chemical Analysis of Iron Meteorites Using a Hand-Held X-Ray Fluorescence Spectrometer. Geostandards and Geoanalytical Research
[doi:10.1111/j.1751-908X.2014.00291.x]
Published by arrangement with John Wiley & Sons

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

^aMax Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077, Göttingen

The Dawn mission’s Framing Camera (FC) observed asteroid (4) Vesta in 2011 and 2012 using seven color filters and one clear filter from different orbits. In the present paper we analyze recalibrated HAMO color cubes (spatial resolution ∼60 m/pixel) with a focus on Dark Material (DM). We present a definition of highly concentrated DM based on spectral parameters, subsequently map the DM across the Vestan surface, geologically classify DM, study its spectral properties on global and local scales, and finally, compare the FC in-flight color data with laboratory spectra.
We have discovered an absorption band centered at 0.72 μm in localities of DM that show the lowest albedo values by using FC data as well as spectral information from Dawn’s imaging spectrometer VIR. Such localities are contained within impact-exposed outcrops on inner crater walls and ejecta material. Comparisons between spectral FC in-flight data, and laboratory spectra of meteorites and mineral mixtures in the wavelength range 0.4 to 1.0 μm, revealed that the absorption band can be attributed to the mineral serpentine, which is typically present in CM chondrites. Dark material in its purest form is rare on Vesta’s surface and is distributed globally in a non-uniform manner. Our findings confirm the hypothesis of an exogenic origin of the DM by the infall of carbonaceous chondritic material, likely of CM type. It further confirms the hypothesis that most of the DM was deposited by the Veneneia impact.

Reference
Nathues et al. (in press) Detection of Serpentine in Exogenic Carbonaceous Chondrite Material on Vesta from Dawn FC Data. Icarus
[doi:10.1016/j.icarus.2014.06.003]
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Louise Alexander^1,2, Joshua F. Snape^2,3,4, Ian A. Crawford^1,2, Katherine H. Joy^3,5 and Hilary Downes^1,2

¹Department of Earth and Planetary Science, Birkbeck College, University of London, London, UK
²The Centre for Planetary Sciences at UCL-Birkbeck, London, UK
³Department of Earth Sciences, University College London, London, UK
⁴Department of Physical Sciences, Open University, Milton Keynes, UK
⁵School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK

New data from a petrological and geochemical examination of 12 coarse basaltic fines from the Apollo 12 soil sample 12023,155 provide evidence of additional geochemical diversity at the landing site. In addition to the bulk chemical composition, major, minor, and trace element analyses of mineral phases are employed to ascertain how these samples relate to the Apollo 12 lithological basalt groups, thereby overcoming the problems of representativeness of small samples. All of the samples studied are low-Ti basalts (0.9–5.7 wt% TiO₂), and many fall into the established olivine, pigeonite, and ilmenite classification of Apollo 12 basaltic suites. There are five exceptions: sample 12023,155_1A is mineralogically and compositionally distinct from other Apollo 12 basalt types, with low pigeonite REE concentrations and low Ni (41–55 ppm) and Mn (2400–2556 ppm) concentrations in olivine. Sample 12023,155_11A is also unique, with Fe-rich mineral compositions and low bulk Mg# (=100 × atomic Mg/[Mg+Fe]) of 21.6. Sample 12023,155_7A has different plagioclase chemistry and crystallization trends as well as a wider range of olivine Mg# (34–55) compared with other Apollo 12 basalts, and shows greater similarities to Apollo 14 high-Al basalts. Two other samples (12023,155_4A, and _5A) are similar to the Apollo 12 feldspathic basalt 12038, providing additional evidence that feldspathic basalts represent a lava flow proximal to the Apollo 12 site rather than material introduced by impacts. We suggest that at least one parent magma, and possibly as many as four separate parent magmas, are required in addition to the previously identified olivine, pigeonite, and ilmenite basaltic suites to account for the observed chemical diversity of basalts found in this study.

Reference
Alexander L, Snape JF, Crawford IA, Joy KH and Downes H (in press) Searching for nonlocal lithologies in the Apollo 12 regolith: A geochemical and petrological study of basaltic coarse fines from the Apollo lunar soil sample 12023,155. Meteoritics & Planetary Science
[doi:10.1111/maps.12319]
Published by arrangement with John Wiley & Sons

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Brendt C. Hyde¹, James M. D. Day², Kimberly T. Tait¹, Richard D. Ash³, David W. Holdsworth⁴ and Desmond E. Moser⁵

¹Department of Natural History, Mineralogy, Royal Ontario Museum, Toronto, Ontario, Canada
²Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, California, USA
³Department of Geology, University of Maryland, College Park, Maryland, USA
⁴Robarts Research Institute, Imaging Research Laboratories, London, Ontario, Canada
⁵Department of Earth Sciences, Western University, London, Ontario, Canada

Terrestrial weathering of hot desert achondrite meteorite finds and heterogeneous phase distributions in meteorites can complicate interpretation of petrological and geochemical information regarding parent-body processes. For example, understanding the effects of weathering is important for establishing chalcophile and siderophile element distributions within sulfide and metal phases in meteorites. Heterogeneous mineral phase distribution in relatively coarsely grained meteorites can also lead to uncertainties relating to compositional representativeness. Here, we investigate the weathering and high-density (e.g., sulfide, spinel, Fe-oxide) phase distribution in sections of ultramafic achondrite meteorite Northwest Africa (NWA) 4872. NWA 4872 is an olivine-rich brachinite (Fo_{63.6 ± 0.5}) with subsidiary pyroxene (Fs_9.7 ± 0.1Wo_{46.3 ± 0.2}), Cr-spinel (Cr# = 70.3 ± 1.1), and weathered sulfide and metal. Raman mapping confirms that weathering has redistributed sulfur from primary troilite, resulting in the formation of Fe-oxide (-hydroxide) and marcasite (FeS₂). From Raman mapping, NWA 4872 is composed of olivine (89%), Ca-rich pyroxene (0.4%), and Cr-spinel (1.1%), with approximately 7% oxidized metal and sulfide and 2.3% marcasite-dominated sulfide. Microcomputed tomography (micro-CT) observations reveal high-density regions, demonstrating heterogeneities in mineral distribution. Precision cutting of the largest high-density region revealed a single 2 mm Cr-spinel grain. Despite the weathering in NWA 4872, rare earth element (REE) abundances of pyroxene determined by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) indicate negligible modification of these elements in this mineral phase. The REE abundances of mineral grains in NWA 4872 are consistent with formation of the meteorite as the residuum of the partial melting process that occurred on its parent body. LA-ICP-MS analyses of sulfide and alteration products demonstrate the mobility of Re and/or Os; however, highly siderophile element (HSE) abundance patterns remain faithful recorders of processes acting on the brachinite parent body(ies). Detailed study of weathering and phase distribution offers a powerful tool for assessing the effects of low-temperature alteration and for identifying robust evidence for parent-body processes.

Reference
Hyde BC, Day JMD, Tait KT, Ash RD, Holdsworth DW and Moser DE (in press) Characterization of weathering and heterogeneous mineral phase distribution in brachinite Northwest Africa 4872. Meteoritics & Planetary Science
[doi:10.1111/maps.12320]
Published by arrangement with John Wiley & Sons

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T. Öhman^1,2,3, G. Y. Kramer^1,2 and D. A. Kring^1,2

¹Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA
²Center for Lunar Science and Exploration, NASA Lunar Science Institute
³Now at Arctic Planetary Science Institute, Rovaniemi, Finland

We used Moon Mineralogy Mapper (M³), Arecibo and Mini-RF radar, and Diviner radiometer data with Lunar Reconnaissance Orbiter (LRO) Camera and Kaguya Terrain Camera images to characterize the target, ejecta, and impact melt-rich lithologies in and around lunar central peak crater Kepler. M³ data indicate the impact melt rocks of crater floor to be high-Ca pyroxene dominated, distinct from the low-Ca pyroxene-dominated crater wall. The central uplift is high-Ca pyroxene dominated, and has higher albedo. These observations are consistent with thin mare basalts underlain by noritic Imbrium ejecta, underlain by gabbroic crustal material. M³ data reveal an enigmatic, splash-like feature of melt-rich material on the southeastern (uprange) crater wall and flank. M³ data also highlight halos around Kepler. In detail the halos are slightly variable, but in broad terms they define a consistent feature, offset to the inferred downrange direction, and interpreted to reflect the distribution of glass-bearing impact breccia. The radar data sets show most of the proximal ejecta to be radar-bright. However, Diviner rock abundance data do not indicate the presence of blocks on the surface nor can they be seen using LRO Narrow Angle Camera images. Thus, the blocks giving rise to the enhanced radar signal are buried. Beyond the radar-bright zone, a subtle radar-dark halo emerges, coincident with a region of very low rock abundance in Diviner data. This multidisciplinary approach provides a robust analysis of the main characteristics of a lunar complex crater and reveals previously unidentified features related to the distribution of impact melt.

Reference
Öhman T, Kramer GY and Kring DA (in press) Characterization of melt and ejecta deposits of Kepler crater from remote sensing data. Journal of Geophysical Research: Planets
[doi:10.1002/2013JE004501]
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C.D. Neish^a, J. Madden^b, L.M. Carter^c, B.R. Hawke^d, T. Giguere^d,e, V.J. Bray^f, G.R. Osinski^g, J.T.S. Cahill^h

^aDepartment of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL, 32901
^bFranklin and Marshall College, Lancaster, PA, 17603
^cNASA Goddard Space Flight Center, Greenbelt, MD, 20771
^dUniversity of Hawai’i at Manoa, Honolulu, HI, 96822
^eIntergraph Corporation, Box 75330, Kapolei, HI, 96707
^fLunar and Planetary Laboratory, University of Arizona, Tucson, AZ, 85721
^gCentre for Planetary Science and Exploration, Departments of Earth Sciences and Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7
^hThe Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723

In this study, we analyzed the distribution and properties of 146 craters with impact melt deposits exterior to their rims. Many of these craters were only recently discovered due to their unusual radar properties in the near-global Mini-RF data set. We find that most craters with exterior deposits of impact melt are small, ⩽ 20 km, and that the smallest craters have the longest melt flows relative to their size. In addition, exterior deposits of impact melt are more common in the highlands than the mare. This may be the result of differing target properties in the highlands and mare, the difference in titanium content, or the greater variation of topography in the highlands. We find that 80% of complex craters and 60% of simple craters have melt directions that are coincident or nearly coincident with the lowest point in their rim, implying that pre-existing topography plays a dominant role in melt emplacement. This is likely due to movement during crater modification (complex craters) or breached crater rims (simple craters). We also find that impact melt flows have very high circular polarization ratios compared to other features on the Moon. This suggests that their surfaces are some of the roughest material on the Moon at the centimeter to decimeter scale, even though they appear smooth at the meter scale.

Reference
Neish CD, Madden J, Carter LM, Hawke BR, Giguere T, Bray VJ, Osinski GR and Cahill JTS (in press) Global distribution of lunar impact melt flows. Icarus
[doi:10.1016/j.icarus.2014.05.049]
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