M. Mommert¹, D. Farnocchia², J. L. Hora³, S. R. Chesley², D. E. Trilling¹, P. W. Chodas², M. Mueller⁴, A. W. Harris⁵, H. A. Smith³ and G. G. Fazio³

¹Department of Physics and Astronomy, Northern Arizona University, P.O. Box 6010, Flagstaff, AZ 86011, USA
²Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
³Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 65, Cambridge, MA 02138-1516, USA
⁴SRON Netherlands Institute for Space Research, Postbus 800, 9700-AV Groningen, The Netherlands
⁵DLR Institute of Planetary Research, Rutherfordstrasse 2, D-12489 Berlin, Germany

We report on observations of near-Earth asteroid 2011 MD with the Spitzer Space Telescope. We have spent 19.9 hr of observing time with channel 2 (4.5 μm) of the Infrared Array Camera and detected the target within the 2σ positional uncertainty ellipse. Using an asteroid thermophysical model and a model of nongravitational forces acting upon the object, we constrain the physical properties of 2011 MD, based on the measured flux density and available astrometry data. We estimate 2011 MD to be (6) m in diameter with a geometric albedo of 0.3 (uncertainties are 1σ). We find the asteroid’s most probable bulk density to be (1.1) g cm^-3, which implies a total mass of (50–350) t and a macroporosity of ≥65%, assuming a material bulk density typical of non-primitive meteorite materials. A high degree of macroporosity suggests that 2011 MD is a rubble-pile asteroid, the rotation of which is more likely to be retrograde than prograde.

Reference
Mommert M, Farnocchia D, Hora JL, Chesley SR, Trilling DE, Chodas PW, Mueller M, Harris AW, Smith HA and Fazio GG (in press) Physical properties of near-Earth asteroid 2011 MD. The Astrophysical Journal Letters 789:L22.
[doi:10.1088/2041-8205/789/1/L22]
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Valery Shuvalov¹ and Rainer Gersonde²

¹Institute of Geosphere Dynamics RAS, Moscow, Russia
²Alfred Wegener Institut fur Polar- und Meeresforschung, Bremerhaven, Germany

The results of numerical simulations of the Eltanin impact are combined with the available geological data in order to reconstruct the impact dynamics and to get some constraints on the impact parameters. Numerical simulations show that the Eltanin projectile size should be less than 2 km for a 45° oblique impact and less than 1.5 km for a vertical impact. On the other hand, we demonstrate that the projectile diameter cannot be considerably smaller than 1 km; otherwise, the impact-induced water flow cannot transport eroded sediments across large distances. The maximum displacement approximately equals the water crater radius and rapidly decreases with increasing distances. Numerical simulations also show that ejecta deposits strongly depend on impact angle and projectile size and, therefore, cannot be used for reliable estimates of the initial projectile mass. The initial amplitudes of tsunami-like waves are estimated. The presence of clay-rich sediments, typical for the abyssal basins in cores PS2709 and PS2708 on the Freeden Seamounts (Bellingshausen Sea, Southern Ocean) combined with numerical data allow us to suggest a probable point of impact to the east of the seamounts. The results do not exclude the possibility that a crater in the ocean bottom may exist, but such a structure has not been found yet.

Reference
Shuvalov V and Gersonde R (in press) Constraints on interpretation of the Eltanin impact from numerical simulations. Meteoritics & Planetary Science
[doi:10.1111/maps.12326]
Published by arrangement with John Wiley & Sons

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Francis Albarède¹, Emmanuelle Albalat¹ and Cin-Ty A. Lee²

¹Ecole Normale Supérieure de Lyon and CNRS, Lyon, France
²Rice University, Department of Earth Sciences, Houston, Texas, USA

The notion of a dry Moon has recently been challenged by the discovery of high water contents in lunar apatites and in melt inclusions within olivine crystals from two pyroclastic glasses. The highest and most compelling water contents were found in pyroclastic glasses that are not very common on the lunar surface. To obtain more representative constraints on the volatile content of the lunar interior, we measured the Zn content, a moderately volatile element, of mineral and rock fragments in lunar soils collected during Apollo missions. We here confirm that the Moon is significantly more depleted in Zn than the Earth. Combining Zn with existing K and Rb data on similar rocks allows us to anchor a new volatility scale based on the bond energy of nonsiderophile elements in their condensed phases. Extrapolating the volatility curve to H shows that the bulk of the lunar interior must be dry (≤1 ppm). This contrasts with the water content of the mantle sources of pyroclastic glasses, inferred to contain up to approximately 40 ppm water based on H₂O/Ce ratios. These observations are best reconciled if the pyroclastic glasses derive from localized water-rich heterogeneities in a dominantly dry lunar interior. We argue that, although late addition of 0.015% of a chondritic veneer to the Moon seems required to explain the abundance of platinum group elements (Day et al. 2007), the volatile content of the added material was clearly heterogeneous.

Reference
 F, Albalat E and Lee C-T A (in press) An intrinsic volatility scale relevant to the Earth and Moon and the status of water in the Moon. Meteoritics & Planetary Science
[doi:10.1111/maps.12331]
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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]
Published by arrangement with John Wiley & Sons

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Wei Wang¹ and Zhuo Li^2,3

¹National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, China
²Department of Astronomy and Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
³Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China

A deep hard X-ray survey of the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellite has detected for the first time non-thermal emission up to 90 keV in the Tycho supernova (SN) remnant. Its 3–100 keV spectrum is fitted with a thermal bremsstrahlung of kT ~ 0.81 ± 0.45 keV plus a power-law model of Γ ~ 3.01 ± 0.16. Based on diffusive shock acceleration theory, this non-thermal emission, together with radio measurements, implies that the Tycho remnant may not accelerate protons up to >PeV but to hundreds TeV. Only heavier nuclei may be accelerated to the cosmic ray spectral “knee.” In addition, using INTEGRAL, we search for soft gamma-ray lines at 67.9 and 78.4 keV that come from the decay of radioactive ⁴⁴Ti in the Tycho remnant. A bump feature in the 60–90 keV energy band, potentially associated with the ⁴⁴Ti line emission, is found with a marginal significance level of ~2.6σ. The corresponding 3σ upper limit on the ⁴⁴Ti line flux amounts to 1.5 × 10^-5 photon cm^-2 s^-1. Implications on the progenitor of the Tycho SN, considered to be a Type Ia SN prototype, are discussed.

Reference
Wang W and Li Z (2014) Hard X-ray emission and 44Ti line features of the Tyco supernova remnant . The Astrophysical Journal 189:123.
[doi:10.1088/0004-637X/789/2/123]

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Noguchi, T¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Faculty of Arts and Science, Kyushu University, Nishi-ku, Fukuoka, Japan

We observed cross sectional ultra-thin sections near the surface of 12 particles recovered from the S-type asteroid Itokawa by the Hayabusa spacecraft in 2010, using spherical aberration–corrected STEM and conventional TEM. Although their mineralogy is almost identical to the equilibrated LL chondrites and therefore basically anhydrous, micrometer-to-submicrometer-sized sylvite was identified on the surface of Itokawa particle RA-QD02-0034. Separately, micrometer-sized halite was also identified on the surface of Itokawa particle RA-QD02-0129. Detailed inspection of the sample processing procedures at the JAXA’s Planetary Materials Sample Curation Facility and textural observation of the sylvite and halite indicate that they were clearly present on two Itokawa particles before they were removed from Clean Chamber #2 at JAXA. However, there is no direct evidence for their extraterrestrial origin at present. If the sylvite and halite are extraterrestrial, their presence suggests that they may be more abundant on the surface of S-type asteroids than previously thought.

Reference
Noguchi et al. (in press) Sylvite and halite on particles recovered from 25143 Itokawa: A preliminary report. Meteoritics & Planetary Science
[doi:10.1111/maps.12333]
Published by arrangement with John Wiley & Sons

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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]
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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]
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