Michael S. Kelley^a,1,2, Michael J. Gaffey^b,1, Vishnu Reddy^c,1, Juan A. Sanchez^d,1

^aDepartment of Geology and Geography, Georgia Southern University, Statesboro, Georgia 30460
^bDepartment of Space Studies, University of North Dakota, Grand Forks, North Dakota 58202
^cPlanetary Science Institute, Tucson, Arizona 85719
^dMax Planck Institute for Solar System Research, Katlenburg-Lindau, Germany
¹Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement No. NNX08AE38A with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program.
²Currently at Science Mission Directorate, NASA Headquarters, Washington DC

Near-Earth asteroids (NEAs) are interesting as both a threat to the Earth and as the immediate sources for most meteorites. We observed NEA (4953) 1990 MU using the NASA Infrared Telescope Facility (IRTF) and University of Hawaii (UH) telescopes on Mauna Kea to constrain its surface composition and origin. The surface composition of 1990 MU is similar to ordinary chondrites (H chondrites). The calculated olivine and pyroxene chemistry of 1990 MU (Fa_13.5±1.3 and Fs_12.7±1.4) are consistent with the olivine and pyroxene chemistry ranges for H chondrites (Fa_15-21 and Fs_13-19) (Dunn et al. 2010), although the estimated Fa value is at the lower end of H chondrite range. The olivine abundance ratio of 1990 MU (0.57±0.03) is slightly higher but not inconsistent with H chondrites (0.47-0.55±0.03). The radar circular polarization ratio (same circular polarization state or SC/opposite circular polarization state or OC) (Benner et al. 2008) of 1990 MU is 0.36±0.03, which is higher than the mean SC/OC ratio for S-type NEAs (0.270±0.079). 1990 MU SC/OC value is also higher than those of (25143) Itokawa (0.27±0.04), (4179) Toutatis (0.29±0.01) and (433) Eros (0.28±0.06) suggesting a rougher surface at decimeter scale (Benner et al. 2008). We constrained the diameter of 1990 MU (4.4 km) using the average albedo at 0.55 μm of H chondrites (0.21) and absolute magnitude (H) of 14.1 (Flower and Chillemi, 1992). This diameter is higher than the 2.8 km value from Harris et al. (2011) using an albedo of 0.52 for 1990 MU. This albedo value is unusually high for H chondrites, which have an albedo range of 0.12-0.30. We compared olivine and pyroxene chemistries of 1990 MU with main belt asteroid (6) Hebe, probable parent body of H chondrite meteorites and IIE irons (Gaffey and Gilbert, 1998), and found that 1990 MU has more high-calcium pyroxene than Hebe. Fayalite and ferrosilite values of the two asteroids are consistent with H chondrites but don’t overlap each other. The differences could be due to compositional variations observed on Hebe by Gaffey and Gilbert (1998), although the observed rotational variation in spectral parameters does not match well with those of 1998 MU.

Reference
Kelley MS, Gaffey MJ, Reddy V and Sanchez JA (2014) Surface Composition of Near-Earth Asteroid (4953) 1990 MU: Possible Fragment of (6) Hebe. Icarus
[doi:10.1016/j.icarus.2014.01.015]
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Richard C. Greenwood^a, Jean-Alix Barrat^b, Akira Yamaguchi^c, Ian A. Franchi^a, Edward R.D. Scott^d, William F. Bottke^e, Jenny M. Gibson^a

^aPlanetary and Space Sciences, Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom
^bCNRS UMR 6538 (Domaines Océaniques), U.B.O.-I.U.E.M., Place Nicolar Copernic, 29280 Plouzané Cedex, France
^cNational Institute of Polar Research, Tokyo 190-8518, Japan
^dHawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, HI 96822, USA
^eSouthwest Research Institute and NASA Lunar Science Institute, 1050 Walnut Street, Suite 400, Boulder, CO 80302, USA

Oxygen isotope measurements of a suite of 22 diogenites demonstrate that they have a restricted range of Δ¹⁷O values: . These results indicate that the diogenites form a single population consistent with a single parent body source, rather than multiple sources as has recently been suggested. Our previously published analysis of eucrites and cumulate eucrites (n=34) give very similar results to the diogenites, with  and confirm that diogenites and eucrites are from the same parent asteroid. The isotopic homogeneity displayed by diogenites, eucrites and cumulate eucrites, provides strong evidence for an early large-scale melting event on the HED parent body, possibly resulting in the formation of a magma ocean. The paradox, whereby diogenites show isotopic evidence in favor of global melting, but also geochemical features indicative of late stage interaction with eucritic crust, may reflect a rapid transition from global to serial magmatism on their parent body. The fact that all the lithologically varied HED units have an isotopically homogeneous composition supports the proposal that they are derived from a single, large, diverse asteroid, most likely 4 Vesta. The recent suggestion that the HEDs are not from Vesta, but instead represent material from the same asteroidal source as the main-group pallasites and IIIAB irons can be excluded by our oxygen isotope data.

Reference
Greenwood RC, Barrat J-A, Yamaguchi A, Franchi IA, Scott ERD, Bottke WF and Gibson JM (2014) The oxygen isotope composition of diogenites: Evidence for early global melting on a single, compositionally diverse, HED parent body. Earth and Planetary Science Letters 390:165–174.
[doi:10.1016/j.epsl.2013.12.011]
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Pasquale Tricarico

Planetary Science Institute, Tucson, AZ 85719, USA

The hydrostatic equilibrium of multi-layer bodies lacks a satisfactory theoretical treatment despite its wide range of applicability. Here we show that by using the exact analytical potential of homogeneous ellipsoids we can obtain recursive analytical solutions and an exact numerical method for the hydrostatic equilibrium shape problem of multi-layer planets and synchronous moons. The recursive solutions rely on the series expansion of the potential in terms of the polar and equatorial shape eccentricities, while the numerical method uses the exact potential expression. These solutions can be used to infer the interior structure of planets and synchronous moons from their observed shape, rotation, and gravity. When applied to the dwarf planet Ceres, we show that it is most likely a differentiated body with an icy crust of equatorial thickness 30-90 km and a rocky core of density 2.4-3.1 g cm^-3. For synchronous moons, we show that the J₂/C₂₂  10/3 and the (b – c)/(a – c)  1/4 ratios have significant corrections of order Ω²/(πGρ), with important implications for how their gravitational coefficients are determined from fly-by radio science data and for how we assess their hydrostatic equilibrium state.

Reference
Tricarico P (2014) Multi-layer Hydrostatic Equilibrium of Planets and Synchronous Moons: Theory and Application to Ceres and to Solar System Moons. The Astrophysical Journal 782:99.
[doi:10.1088/0004-637X/782/2/99]

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Stephen M. Elardo^1,*, Charles K. Shearer Jr.¹, Amy L. Fagan^2,3, Lars E. Borg⁴, Amy M. Gaffney⁴, Paul V. Burger¹, Clive R. Neal², Vera A. Fernandes⁵, Francis M. McCubbin¹

¹Department of Earth & Planetary Sciences, Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA
²Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, Notre Dame, Indiana, USA
³Lunar & Planetary Institute, USRA, Houston, Texas, USA
⁴Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, California, USA
⁵Museum für Naturkunde- Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany

Northwest Africa (NWA) 4734 is an unbrecciated basaltic lunar meteorite that is nearly identical in chemical composition to basaltic lunar meteorites NWA 032 and LaPaz Icefield (LAP) 02205. We have conducted a geochemical, petrologic, mineralogic, and Sm-Nd, Rb-Sr, and Ar-Ar isotopic study of these meteorites to constrain their petrologic relationships and the origin of young mare basalts. NWA 4734 is a low-Ti mare basalt with a low Mg* (36.5) and elevated abundances of incompatible trace elements (e.g., 2.00 ppm Th). The Sm-Nd isotope system dates NWA 4734 with an isochron age of 3024 ± 27 Ma, an initial ε_Nd of +0.88 ± 0.20, and a source region ¹⁴⁷Sm/¹⁴⁴Nd of 0.201 ± 0.001. The crystallization age of NWA 4734 is concordant with those of LAP 02205 and NWA 032. NWA 4734 and LAP 02205 have very similar bulk compositions, mineral compositions, textures, and ages. Their source region ¹⁴⁷Sm/¹⁴⁴Nd values indicate that they are derived from similar, but distinct, source materials. They probably do not sample the same lava flow, but rather are similarly sourced, but isotopically distinct, lavas that probably originate from the same volcanic complex. They may have experienced slightly different assimilation histories in route to eruption, but can be source-crater paired. NWA 032 remains enigmatic, as its source region ¹⁴⁷Sm/¹⁴⁴Nd definitively precludes a simple relationship with NWA 4734 and LAP 02205, despite a similar bulk composition. Their high Ti/Sm, low (La/Yb)_N, and Cl-poor apatite compositions rule out the direct involvement of KREEP. Rather, they are consistent with low-degree partial melting of late-formed LMO cumulates, and indicate that the geochemical characteristics attributed to urKREEP are not unique to that reservoir. These and other basaltic meteorites indicate that the youngest mare basalts originate from multiple sources, and suggest that KREEP is not a prerequisite for the most recent known melting in the Moon.

Reference
Elardo SM, Shearer CK, Fagan AL, Borg LE, Gaffney AM, Burger PV, Neal CR, Fernandes VA and McCubbin FM (in press) The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205. Meteoritics & Planetary Science
[doi:10.1111/maps.12239]
Published by arrangement with John Wiley & Sons

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Ann M. Ollila¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Princeton University, Princeton, NJ 08540, USA

The ChemCam instrument package on the Mars rover, Curiosity, provides new capabilities to probe the abundances of certain trace elements in the rocks and soils on Mars using the laser-induced breakdown spectroscopy technique. We focus on detecting and quantifying Li, Ba, Rb, and Sr in targets analyzed during the first 100 sols, from Bradbury Landing Site to Rocknest. Univariate peak area models and multivariate partial least squares models are presented. Li, detected for the first time directly on Mars, is generally low (<15 ppm). The lack of soil enrichment in Li, which is highly fluid mobile, is consistent with limited influx of subsurface waters contributing to the upper soils. Localized enrichments of up to ~60 ppm Li have been observed in several rocks but the host mineral for Li is unclear. Bathurst_Inlet is a fine-grained bedrock unit in which several analysis locations show a decrease in Li and other alkalis with depth, which may imply that the unit has undergone low-level aqueous alteration that has preferentially drawn the alkalis to the surface. Ba (~1000 ppm) was detected in a buried pebble in the Akaitcho sand ripple and it appears to correlate with Si, Al, Na, and K, indicating a possible feldspathic composition. Rb and Sr are in the conglomerate Link at abundances >100 ppm and >1000 ppm, respectively. These analysis locations tend to have high Si and alkali abundances, consistent with a feldspar composition. Together, these trace element observations provide possible evidence of magma differentiation and aqueous alteration.

Reference
Ann M. Ollila et al. (in press) Trace element geochemistry (Li, Ba, Sr, and Rb) using Curiosity’s ChemCam: Early results for Gale crater from Bradbury Landing Site to Rocknest. Journal of Geophysical Research: Planets
[doi:10.1002/2013JE004517]
Published by arrangement with John Wiley & Sons

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Nancy L. Chabot^a, E. Alex Wollack^b, Rachel L. Klima^a and Michelle E. Minitti^a

^aThe Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
^bPrinceton University, Princeton, NJ 08540, USA

The recent discovery of high S concentrations on the surface of Mercury by spacecraft measurements from the MESSENGER mission provides the potential to place new constraints on the composition of Mercuryʼs large metallic core. In this work, we conducted a set of systematic equilibrium metal–silicate experiments that determined the effect of different metallic compositions in the Fe–S–Si system on the S concentration in the coexisting silicate melt. We find that metallic melts with a range of S and Si combinations can be in equilibrium with silicate melts with S contents consistent with Mercuryʼs surface, but that such silicate melts contain Fe contents lower than measured for Mercuryʼs surface. If Mercuryʼs surface S abundance is representative of the planetʼs bulk silicate composition and if the planet experienced metal–silicate equilibrium during planetary core formation, then these results place boundaries on the range of possible combinations of Si and S that could be present as the light elements in Mercuryʼs core and suggest that Mercuryʼs core likely contains Si. Except for core compositions with extreme abundances of Si, bulk Mercury compositions calculated by using the newly determined range of potential S and Si core compositions do not resemble primitive meteorite compositions.

Reference
Chabot NL, Wollack EA, Klima RL and Minitti ME (2014) Experimental constraints on Mercuryʼs core composition. Earth and Planetary Science Letters 390:199–208.
[doi:10.1016/j.epsl.2014.01.004]
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N.G. Rudraswami^a, M. Shyam Prasad^a, J.M.C. Plane^b, T. Berg^c, W. Feng^b and S. Balgar^a

^aNational Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403 004, India
^bSchool of Chemistry, University of Leeds, Leeds LS29JT, UK
^cInstitut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55128 Mainz, Germany

Out of the three basic cosmic spherule types collected from the seafloor, RMNs (Refractory Metal Nuggets) have been reported from I-type spherules commonly, rarely from S-type spherules and never from the G-type spherules. Nuggets in the I-type cosmic spherules have formed by melting and complete oxidation during atmospheric entry, whereas no clear understanding emerged so far regarding the formation of the rare nuggets in S-type spherules. We collected cosmic spherules by raking the deep seafloor with magnets, and carried out systematic and sequential grinding, polishing and electron microscopic investigations on 992 cosmic spherules to identify RMNs. Fifty-four nuggets (RMNs) are identified, out of which 23, 26, and 5 nuggets are recovered from 23 I-, 21 S- and 5 G-type cosmic spherules, respectively.
The nuggets in all the three spherule types follow a pattern indicative of their formation by metal segregation during atmospheric entry due to heating and oxidation, however, there are differences in their elemental distribution patterns. The refractory metal elements (RMEs) in the I-type spherules show a sequence of volatilization form a chondritic source, however, the relatively volatile RMEs in these spherules seem to be either depleted or distributed in numerous smaller nuggets. However, RMNs in the G-type spherules show closer conformity to CI chondrites and do not have a large volatile RME depletion. Whereas, the RMEs in the nuggets found in the S-type spherules are enriched in the volatile as well as the refractory elements. Also all the spherules show enrichment patterns and elemental ratios that are close to CI composition for refractory elements suggesting a common mechanism of formation. Pulse heating during atmospheric entry seems to be an efficient mechanism for RME segregation into nuggets. The patterns of RME enrichment and elemental ratios when compared with the nuggets in CAIs, show marked variations, outlining their differences in the process of formation. In addition, we also discovered a fremdling-like object in a cosmic spherule which has a nugget encased in Fe-Ni and sulfide phases, similar to those typically observed in CAIs of CV or CO chondrites. The atmospheric entry for this rare cosmic spherule appears to have taken place at a high zenith angle with a low entry velocity, so that its volatile phases are well preserved.

Reference
Rudraswami NG, Prasad MS, Plane JMC, Berg T, Feng W and Balgar S (in press) Refractory Metal Nuggets In Different Types Of Cosmic Spherules. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2014.01.026]
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Matthew R.M. Izawa^a, Edward A. Cloutis^a, Daniel M. Applin^a, Michael A. Craig^b, Paul Mann^a and Matthew Cuddy^a

^aHyperspectral Optical Sensing for Extraterrestrial Reconnaissance Laboratory, Dept. Geography, University of Winnipeg, 515 Portage Avenue, Winnipeg, Manitoba R3B 2E9, Canada
^bDepartment of Earth Sciences/Centre for Planetary Science and Exploration, University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada

Reflectance spectroscopy of Apollo lunar soil samples curated in an air- and water-free, sealed environment since recovery and return to Earth has been carried out under water-, oxygen-, CO₂– and organic-controlled conditions. Spectra of these pristine samples contain features near 3 μm wavelength similar to those observed from the lunar surface by the Chandrayaan-1 Moon Mineralogy Mapper (M³), Cassini Visual and Infrared Mapping Spectrometer (VIMS), and Deep Impact Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) High-Resolution Instrument (HRI) instruments. Spectral feature characteristics and inferred OH/H₂O concentrations are within the range of those observed by spacecraft instruments. These findings confirm that the 3 μm feature from the lunar surface results from the presence of hydration in the form of bound OH and H₂O. Implantation of solar wind H⁺ appears to be the most plausible formation mechanism for most of the observed lunar OH and H₂O.

Reference
Izawa MRM, Cloutis EA, Applin DM, Craig MA, Mann P and Cuddy M (2014) Laboratory spectroscopic detection of hydration in pristine lunar regolith. Earth and Planetary Science Letters 390:157–164.
[doi:10.1016/j.epsl.2014.01.007]
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Jessica J. Barnes^a,b, Romain Tartèse^a, Mahesh Anand^a,b, Francis M. McCubbin^c, Ian A. Franchi^a, Natalie A. Starkey^a, Sara S. Russell<sup>b

a</sup>Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
^bDepartment of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK
^cInstitute of Meteoritics, University of New Mexico, 200 Yale Blvd SE, Albuquerque, NM, USA

The recent discoveries of hydrogen (H) bearing species on the lunar surface and in samples derived from the lunar interior have necessitated a paradigm shift in our understanding of the water inventory of the Moon, which was previously considered to be a ‘bone-dry’ planetary body. Most sample-based studies have focused on assessing the water contents of the younger mare basalts and pyroclastic glasses, which are partial-melting products of the lunar mantle. In contrast, little attention has been paid to the inventory and source(s) of water in the lunar highlands rocks which are some of the oldest and most pristine materials available for laboratory investigations, and that have the potential to reveal the original history of water in the Earth–Moon system. Here, we report in-situ measurements of hydroxyl (OH) content and H isotopic composition of the mineral apatite from four lunar highlands samples (two norites, a troctolite, and a granite clast) collected during the Apollo missions. Apart from troctolite in which the measured OH contents in apatite are close to our analytical detection limit and its H isotopic composition appears to be severely compromised by secondary processes, we have measured up to ~2200 ppm OH in the granite clast with a weighted average δD of , and up to ∼3400 ppm OH in the two norites (77215 and 78235) with weighted averageδD values of −281±49‰ and −27±98‰, respectively. The apatites in the granite clast and the norites are characterised by higher OH contents than have been reported so far for highlands samples, and have H isotopic compositions similar to those of terrestrial materials and some carbonaceous chondrites, providing one of the strongest pieces of evidence yet for a common origin for water in the Earth–Moon system. In addition, the presence of water, of terrestrial affinity, in some samples of the earliest-formed lunar crust suggests that either primordial terrestrial water survived the aftermath of the putative impact-origin of the Moon or water was added to the Earth–Moon system by a common source immediately after the accretion of the Moon.

Reference
Barnes JJ, Tartèse R, Anand M, McCubbin FM, Franchi IA, Starkey NA, Russell SS (2014) The origin of water in the primitive Moon as revealed by the lunar highlands samples. Earth and Planetary Science Letters390:244–252.
[doi:10.1016/j.epsl.2014.01.015]
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L. J. Hallis^a,b,c, M. Anand^b,c, S. Strekopytov^c

^aHawai‘i Institute of Geophysics and Planetology, Pacific Ocean Science & Technology (POST) Building, University of Hawai‘i, 1680 East-West Road, Honolulu, HI 96822, US
^bDepartment of Physical Sciences, CEPSAR, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
^cDepartment of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom

The heterogeneous-source model of mare basalt formation indicates that Lunar Magma Ocean (LMO) overturn produced an uneven mixture of early-formed olivine and pyroxene, and late-formed, ilmenite-rich cumulates, which subsequently partially melted to give rise to mare magmas. These heterogeneous cumulate source regions would not only have been characterised by different mineral modal abundances, but also by different trace element compositions. The aim of this work was to investigate the petrology and geochemistry of a diverse suite of Apollo mare basalts, and utilise trace-element modelling in order to understand their petrogenetic history. Chemical modelling confirms that the mare basalts were produced by relatively small degrees of partial melting (< 10%) of the LMO cumulates, and that the dominant melting type (batch vs. fractional) varies among different basalt groups. Similarly, single-source mineralogy cannot be applied to all mare basalt types, confirming that the lunar mantle was heterogeneous at the time of generation of mare magmas. Plagioclase is not required in the source of most mare basalts, with the notable exception of the Apollo 14 high-Al basalts. Addition of more than 1% plagioclase to the source of other basalts produces weaker negative Eu anomalies than those observed in the samples. AFC calculations demonstrate the compositional differences between materials assimilated into the Apollo 14 high-Al and Apollo 11 high-K mare basalt partial melts, highlighting the complexities of mare basalt petrogenesis.

Reference
Hallis LJ, Anand M and Strekopytov S (in press) Trace-element modelling of mare basalt parental melts: Implications for a heterogeneous lunar mantle. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2014.01.012]
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