^1,2Francis M. McCubbin et al. (>10)*
¹Institute of Meteoritics, University of New Mexico, 200 Yale Blvd SE, Albuquerque, New Mexico 87131, U.S.A.
²Department of Earth and Planetary Sciences, University of New Mexico, 200 Yale Blvd SE, Albuquerque, New Mexico 87131, U.S.A.
*Find the extensive, full author and affiliation list on the publishers website

Many studies exist on magmatic volatiles (H, C, N, F, S, Cl) in and on the Moon, within the last several years, that have cast into question the post-Apollo view of lunar formation, the distribution and sources of volatiles in the Earth-Moon system, and the thermal and magmatic evolution of the Moon. However, these recent observations are not the first data on lunar volatiles. When Apollo samples were first returned, substantial efforts were made to understand volatile elements, and a wealth of data regarding volatile elements exists in this older literature. In this review paper, we approach volatiles in and on the Moon using new and old data derived from lunar samples and remote sensing. From combining these data sets, we identified many points of convergence, although numerous questions remain unanswered.

The abundances of volatiles in the bulk silicate Moon (BSM), lunar mantle, and urKREEP [last ~1% of the lunar magma ocean (LMO)] were estimated and placed within the context of the LMO model. The lunar mantle is likely heterogeneous with respect to volatiles, and the relative abundances of F, Cl, and H2O in the lunar mantle (H2O > F >> Cl) do not directly reflect those of BSM or urKREEP (Cl > H2O ≈ F). In fact, the abundances of volatiles in the cumulate lunar mantle were likely controlled by partitioning of volatiles between LMO liquid and nominally anhydrous minerals instead of residual liquid trapped in the cumulate pile. An internally consistent model for lunar volatiles in BSM should reproduce the absolute and relative abundances of volatiles in urKREEP, the anorthositic primary crust, and the lunar mantle within the context of processes that occurred during the thermal and magmatic evolution of the Moon. Using this mass-balance constraint, we conducted LMO crystallization calculations with a specific focus on the distributions and abundances of F, Cl, and H2O to determine whether or not estimates of F, Cl, and H2O in urKREEP are consistent with those of the lunar mantle, estimated independently from the analysis of volatiles in mare volcanic materials. Our estimate of volatiles in the bulk lunar mantle are 0.54–4.5 ppm F, 0.15–5.3 ppm H2O, 0.26–2.9 ppm Cl, 0.014–0.57 ppm C, and 78.9 ppm S. Our estimates of H2O are depleted compared to independent estimates of H2O in the lunar mantle, which are largely biased toward the “wettest” samples. Although the lunar mantle is depleted in volatiles relative to Earth, unlike the Earth, the mantle is not the primary host for volatiles. The primary host of the Moon’s incompatible lithophile volatiles (F, Cl, H2O) is urKREEP, which we estimate to have 660 ppm F, 300–1250 ppm H2O, and 1100–1350 ppm Cl. This urKREEP composition implies a BSM with 7.1 ppm F, 3–13 ppm H2O, and 11–14 ppm Cl. An upper bound on the abundances of F, Cl, and H2O in urKREEP and the BSM, based on F abundances in CI carbonaceous chondrites, are reported to be 5500 ppm F, 0.26–1.09 wt% H2O, and 0.98–1.2 wt% Cl and 60 ppm F, 27–114 ppm H2O, and 100–123 ppm Cl, respectively.

The role of volatiles in many lunar geologic processes was also determined and discussed. Specifically, analyses of volatiles from lunar glass beads as well as the phase assemblages present in coatings on those beads were used to infer that H2 is likely the primary vapor component responsible for propelling the fire-fountain eruptions that produced the pyroclastic glass beads (as opposed to CO). The textural occurrences of some volatile-bearing minerals are used to identify hydrothermal alteration, which is manifested by sulfide veining and sulfide-replacement textures in silicates. Metasomatic alteration in lunar systems differs substantially from terrestrial alteration due to differences in oxygen fugacity between the two bodies that result in H2O as the primary solvent for alteration fluids on Earth and H2 as the primary solvent for alteration fluids on the Moon (and other reduced planetary bodies). Additionally, volatile abundances in volatile-bearing materials are combined with isotopic data to determine possible secondary processes that have affected the primary magmatic volatile signatures of lunar rocks including degassing, assimilation, and terrestrial contamination; however, these processes prove difficult to untangle within individual data sets. Data from remote sensing and lunar soils are combined to understand the distribution, origin, and abundances of volatiles on the lunar surface, which can be explained largely by solar wind implantation and spallogenic processes, although some of the volatiles in the soils may also be either indigenous to the Moon or terrestrial contamination. We have also provided a complete inventory of volatile-bearing mineral phases indigenous to lunar samples and discuss some of the “unconfirmed” volatile-bearing minerals that have been reported. Finally, a compilation of unanswered questions and future avenues of research on the topic of lunar volatiles are presented, along with a critical analysis of approaches for answering these questions.

Reference
McCubbin FM et al. (2015) Magmatic volatiles (H, C, N, F, S, Cl) in the lunar mantle, crust, and regolith: Abundances, distributions, processes, and Reservoirs. American Mineralogist 100, 1668-1707
Link to Article [doi: 10.2138/am-2015-4934CCBYNCND]

Copyright: The Mineralogical Society of America

¹Yoshihiro Furukawa, ¹Hiromoto Nakazawa, ²Toshimori Sekine, ³Takamichi Kobayashi, ¹Takeshi Kakegawa
¹Department of Earth Science, Tohoku University, 6-3 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8578, Japan
²Department of Earth and Planetary Systems Science, Hiroshima University, 1-3-1 Kagami-yama, Higashi-Hiroshima 739-8526, Japan
³National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

The emergence of life’s building blocks on the prebiotic Earth was the first crucial step for the origins of life. Extraterrestrial delivery of intact amino acids and nucleobases is the prevailing hypothesis for their availability on prebiotic Earth because of the difficulties associated with the production of these organics from terrestrial carbon and nitrogen sources under plausible prebiotic conditions. However, the variety and amounts of these intact organics delivered by meteorites would have been limited. Previous shock–recovery experiments have demonstrated that meteorite impact reactions could have generated organics on the prebiotic Earth. Here, we report on the simultaneous formation of nucleobases (cytosine and uracil) found in DNA and/or RNA, various proteinogenic amino acids (glycine, alanine, serine, aspartic acid, glutamic acid, valine, leucine, isoleucine, and proline), non-proteinogenic amino acids, and aliphatic amines in experiments simulating reactions induced by extraterrestrial objects impacting on the early oceans. To the best of our knowledge, this is the first report of the formation of nucleobases from inorganic materials by shock conditions. In these experiments, bicarbonate was used as the carbon source. Bicarbonate, which is a common dissolved carbon species in CO2-rich atmospheric conditions, was presumably the most abundant carbon species in the early oceans and in post-impact plumes. Thus, the present results expand the possibility that impact-induced reactions generated various building blocks for life on prebiotic Earth in large quantities through the use of terrestrial carbon reservoirs.

Reference
Furukawa Y, Nakazawa H, Sekine T, Kobayashi T, Kakegawa T (2015) Nucleobase and amino acid formation through impacts of meteorites on the early ocean. Earth and Planetary Science Letters (in Press)
Link to Article [doi:10.1016/j.epsl.2015.07.049]
Copyright Elsevier

^1,2C. Lantz, ³R. Brunetto, ¹M. A. Barucci, ³E. Dartois, ⁴J. Duprat, ⁴C. Engrand, ⁴M. Godard, ⁴D. Ledu, ⁵E. Quirico 
¹Laboratoire d’Études Spatiales et d’Instrumentation en Astrophysique (LESIA) – Observatoire de Paris, CNRS (UMR 8109)/UPMC (Paris 6) / Univ. Paris Diderot (Paris 7), 92195 Meudon Cedex, France
²Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex 13, France
³Institut d’Astrophysique Spatiale (IAS), CNRS (UMR 8617)/Université Paris-Sud (Paris 11), 91405 Orsay Cedex, France
⁴Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), IN2P3 – CNRS (UMR 8609)/Université Paris-Sud (Paris 11), 91405 Orsay Cedex, France
⁵Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), Université J. Fournier – Grenoble 1/CNRS-INSU (UMR 5274), 38041 Grenoble Cedex 9, France

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Reference
Lantz C, Brunetto R, Barucci MA, Dartois E, Duprat J, Engrand C, Godard M, Ledu D, Quirico E (2015) Ion irradiation of the Murchison meteorite: Visible to mid-infrared spectroscopic results. Astronomy & Astrophysics 577, A41
Link to Article [dx.doi.org/10.1051/0004-6361/201425398 ]

^1,2Amaury Thiabaud, ^1,2Ulysse Marboeuf, ^1,2,4Yann Alibert, ^1,2Ingo Leya, ^1,3Klaus Mezger
¹Center for Space and Habitability, Universität Bern, 3012 Bern, Switzerland
e-mail: amaury.thiabaud@csh.unibe.ch
²Physikalisches Institut, Universität Bern, 3012 Bern, Switzerland
³Institut für Geologie, Universität Bern, 3012 Bern, Switzerland
⁴On leave from CNRS, Observatoire de Besançon, 25000 Besançon, France

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Reference
Thiabaud A, Marboeuf U, Alibert Y, Leya I, Mezger K (2015) Elemental ratios in stars vs planets. Astronomy & Astrophysics 580, A30
Link to Article [dx.doi.org/10.1051/0004-6361/201525963]

¹Daniel Carrera, ¹Anders Johansen, ¹Melvyn B. Davies
¹Lund ObservatoryDepartment of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden

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Reference
Carrera D, Johansen A, Davies MB (2015) How to form planetesimals from mm-sized chondrules and chondrule aggregates. Astronomy & Astrophysics 579, A43
Link to Article [dx.doi.org/10.1051/0004-6361/201425120]

¹Peter Hoppe, ¹Jan Leitner, ¹János Kodolányi
¹Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, D-55128 Mainz, Germany

We studied about 5000 μm2 of fine-grained matrix material in the Acfer 094 meteorite by high-resolution (nominal 50 nm) NanoSIMS ion imaging for the presence of O-rich presolar (stardust) grains. This approach permits identifying presolar grains down to 150 nm in lower-resolution (nominal 100 nm) ion imaging surveys. The number density of identified presolar grains is a about a factor of two to three higher than what was found by lower-resolution ion imaging studies. The abundances of grains of O isotope Group 3 and 4 are higher than previously found. None of the presolar grains shows the strong enrichments in 16O expected from model predictions for the majority of supernova (SN) grains. Other potential O-rich SN grains, the Group 4 and some of the Group 3 grains, make up 33% by number and 19% by mass. This is clearly higher than the ~10% (by number) inferred before and the 5% (by mass) estimated by a model for stellar dust in the interstellar medium. Our work shows that O-rich SN grains might be more abundant among the population of presolar grains in primitive solar system materials than currently thought, even without the 16O-rich grains as predominantly expected from SN models.

Reference
Hoppe P, Leitner J, Kodolányi J (2015) New Constraints on the Abundances of Silicate and Oxide Stardust from Supernovae in the Acfer 094 Meteorite. Astrophysical Journal 808 L9.
Link to Article [doi:10.1088/2041-8205/808/1/L9]

¹Noriyuki Kawasaki, ¹Chizu Kato, ¹Shoichi Itoh, ¹Shigeyuki Wakaki, ²Motoo Ito, ¹Hisayoshi Yurimoto
¹Department of Natural History Sciences, Hokkaido University, Sapporo, 060-0810, Japan
²Kochi Institute for Core Sample Research, JAMSTEC B200, Monobe, Nankoku, Kochi, 783-8502, Japan

Disequilibrium oxygen isotopic distributions of Ca-Al-rich inclusions (CAIs) correspond to multiple melting events in the solar nebula. 26Al-26Mg systematics may be applicable for age differences among such melting events. We have carried out a coordinated study of detailed petrographic observations and in-situ oxygen and magnesium isotope measurements for a Type C CAI, EK1-04-2, from the Allende CV3 meteorite to determine the melting events and their ages. The CAI consists mainly of spinel, anorthite, olivine, and pyroxene, and has a core and mantle structure. Petrography of the core suggests that the crystallization sequence of the core minerals is from spinel, anorthite, olivine, and to pyroxene. The mantle has the same mineral assemblage as the core, and shows incomplete melting and solidification textures. Oxygen isotopic compositions of the minerals are distributed along the carbonaceous chondrite anhydrous mineral (CCAM) line (δ18O = −44 to +9‰), which indicates to preserve a chemical disequilibrium status in the CAI. Spinel shows a 16O-rich signature (δ18O ∼ −43‰), while anorthite is 16O-poor (δ18O ∼ +8‰). Olivine and pyroxene in the core have the same oxygen isotopic composition (δ18O ∼ −15‰), which indicates their equilibrium. Olivine and pyroxene in the mantle have variable oxygen isotopic compositions and are slightly depleted in 16O (δ18O = −13 to −4‰) compared with the same minerals in the core. The 26Al-26Mg systematics is consistent with the disequilibrium status observed according to the petrography and oxygen isotopes. Spinel is plotted on a line of (26Al/27Al)0 = (3.5 ± 0.2) × 10−5, anorthite is plotted on a line of (−1 ± 5) × 10−7, and olivine and pyroxene in the core are plotted on a line of (−1 ± 7) × 10−6. Plots of olivine and pyroxene in the mantle are scattered below the isochron of these minerals in the core. This study indicates that the EK1-04-2 Type C CAI underwent multiple heating events after the formation of its CAI precursor. The precursor CAI was formed ∼0.4 Myr after the formation of the Solar System defined by canonical CAI formation. At least 1.6 Myr after the precursor CAI formation, the CAI was partially melted and the melt exchanged oxygen isotopes with surrounding 16O-poor nebular gas. 16O-poor olivine and pyroxene in the core crystallized from the melt. Subsequently, Al-rich chondrules accreted onto the CAI, and the CAI experienced partial melting again and recrystallized to form the mantle. The oxygen and magnesium isotopes in anorthite were redistributed during thermal metamorphism in the Allende parent body. Our study reveals that the CAI had been retained in the solar nebula for at least 1.6 Myr and underwent multiple melting events in the nebula, and oxygen and 26Al-26Mg systematics has been partially disturbed depending on crystal sizes by metamorphism on the parent body.

Reference
Kawasaki N, Kato C, Itoh S, Wakaki S, Ito M, Yurimotoa H (2015) 26Al-26Mg chronology and oxygen isotope distributions of multiple melting for a Type C CAI from Allende. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.07.037]

Copyright Elsevier

^1,2Hsin-Wei Chen, ^1,3Typhoon Lee, ¹Der-Chuen Lee, ¹Jiang-Chang Chen
¹Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan, ROC
²School of Earth Sciences, University of Bristol, Bristol, UK
³Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan, ROC

Precise determinations of 48Ca anomalies in Allende calcium–aluminum-rich inclusions (CAIs) are reported in this work. There are endemic positive 48Ca/44Ca anomalies in all analyzed CAIs after normalization to 42Ca/44Ca, and it is clearly shown that there is no simple correlation between 48Ca/44Ca and 50Ti/48Ti anomalies, in agreement with Jungck et al. Compared to the 48Ca/44Ca versus 50Ti/48Ti correlation line defined by differentiated meteorites, reported by Chen et al., the CAIs plot to elevated 50Ti/48Ti. Assuming the 48Ca/44Ca anomalies of both CAIs and differentiated meteorites came from the same source, excess 50Ti anomalies in CAIs can be calculated by subtracting the part associated with 48Ca/44Ca. These excesses show a linear correlation with 138La anomalies, a neutrino-process nuclide. According to current stellar nucleosynthetic models, we therefore suggest that the solar system 48Ca, 50Ti, and 138La isotopic variations are made of mixtures between grains condensed from ejecta of neutron-rich accretion-induced SNe Ia and the O/Ne–O/C zone of core-collapse SNe II.

Reference
Chen H-W, Lee T, Lee D-C, Chen J-C (2015) Correlation of 48Ca, 50Ti, and 138La Heterogeneity in the Allende Refractory Inclusions. Astrophysical Journal 806 L21.

Link to Article [doi:10.1088/2041-8205/806/1/L21]

¹Jean-Philippe Combe, ^2,3Eleonora Ammannito,²Federico Tosi, ²Maria Cristina de Sanctis, ¹Thomas B. McCord, ⁴Carol A. Raymond,³Christopher T. Russell
¹Bear Fight Institute, 22 Fiddler’s Road, P.O. Box 667, Winthrop, WA 98862, USA
²Istituto di Astrofisica e Planetologia Spaziali-Istituto Nazionale di Astrofisica, Rome, Italy
³Institute of Geophysics and Planetary Physics, University of California Los Angeles, CA, USA
⁴Jet Propulsion Laboratory, Pasadena, CA, USA

Vesta’s surface albedo variations and hydrated material content share similar spatial distribution. This observation is consistent with carbonaceous chondrite meteorites as a likely source material for dark surface units observed by the Dawn spacecraft, as presented by numerous publications. While these deposits have been studied extensively by analysis of data from the Framing Camera (FC) and the Visible and Infrared Spectrometer (VIR), we performed a new analysis based on an improved calibration of VIR. First we identified instrument and calibration artifacts, and we therefore developed corrections of the VIR flat field and response function. Then we developed a photometric correction for Vesta based on the lunar model by Shkuratov et al. (1999, Icarus 141), and a semi-analytical inversion of the photometric parameters. This photometric model combines minimization of the scattering effects due to the topography (a disk function) and variations of multiple-scattering with phase angle (the phase function) caused by microscopic physical properties of the regolith. The improved calibration and photometric correction enable more accurate analysis of the spectral properties of Vesta’s surface material, especially the reflectance at 1.4 μm and the 2.8 μm hydroxyl absorption band depth. We produced global and quadrangle maps that are used as a common dataset for this Icarus special issue on Vesta’s surface composition. The joint interpretation of both the 1.4 μm reflectance and the 2.8 μm absorption band depth reveals unusual spectral properties for a number of impact craters and ejecta compared to the rest of Vesta. An area including the Bellicia, Arruntia and Pomponia craters, where olivine might be present, has relatively high reflectance and a strong hydroxyl absorption band. Another area in the vicinity of Capparonia crater has a high content of hydrated materials, although with moderate reflectance and typical pyroxene-rich composition. Ejecta blankets west of Oppia crater have a spectral behavior similar to Capparonia, except for the wider and more complex shape of the hydroxyl absorption band. On the other hand, some low-hydrated areas associated to crater floors and ejecta have higher reflectance and steeper spectral slope than most low-hydrated terrains Vesta. A broad lane that extends from Rheasilvia rim at Matronalia Rupes to the northern regions hosts little to no hydrated materials and exhibits a moderate spectral slope, similar to Rheasilvia’s basin floor. These properties reinforce the hypothesis that the lane is composed of ejecta from Rheasilvia, as indicated by the distribution of pyroxene compositions by previous results from Dawn. A few small and fresh craters exhibit an association between low-reflectance, little to no hydrated materials and a strong positive spectral slope, suggesting optical effects by opaque coatings, as opposed to carbonaceous chondrite deposits, and possible coarser grains.

Reference
Combe J-P, Ammannito E, Tosi F, de Sanctis MC, McCord TB, Raymond CA, Russell CT (2015)
Reflectance properties and hydrated material distribution on Vesta: Global investigation of variations and their relationship using improved calibration of Dawn VIR mapping spectrometer. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.07.034]
Copyright Elsevier

^1,2Vladimir V. Busarev, ³Sergey I. Barabanov, ³Vyacheslav S. Rusakov, ²Vasiliy B. Puzin, ^1,4Valery V. Kravtsov
¹Lomonosov Moscow State University, Sternberg Astronomical Institute, University Avenue 13, 119992 Moscow, Russia
²Institute of Astronomy of Russian Academy of Science, Pyatnitskaya St. 48, 109017 Moscow, Russia
³Division of Mossbauer Spectroscopy, Physical Dep. of Lomonosov Moscow State University, 119992 Moscow, Russia
⁴Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Atacama, Copayapu 485, Copiapo, Chile

Six asteroids including two NEAs, one of which is PHA, accessible for observation in September 2012 were investigated using a low-resolution (R ≈ 100) spectrophotometry in the range 0.35-0.90 μm with the aim to study features of their reflectance spectra. A high-altitude position of our Terskol observatory (3150 m above sea level) favorable for the near-UV and visible-range observations of celestial objects let us probably to detect some new spectral features of the asteroids. Two subtle absorption bands centered at 0.53 and 0.74 μm were found in the reflectance spectra of S-type (32) Pomona and interpreted as signs of presence of pyroxenes in the asteroid surface matter and its different oxidation. Very similar absorption bands centered at 0.38, 0.44 and 0.67-0.71 μm have been registered in the reflectance spectra of (145) Adeona, (704) Interamnia, and (779) Nina of primitive types. We performed laboratory investigations of ground samples of known carbonaceous chondrites, Orguel (CI), Mighei (CM2), Murchison (CM2), Boriskino (CM2), and seven samples of low-iron Mg serpentines as possible analogs of the primitive asteroids. In the course of this work, we discovered an intense absorption band (up to ∼25%) centered at 0.44 μm in reflectance spectra of the low-Fe serpentine samples. As it turned out, the equivalent width of the band has a high correlation with content of Fe3+ (octahedral and tetrahedral) in the samples. It may be considered as a confirmation of the previously proposed mechanism of the absorption due to electronic transitions in exchange-coupled pairs (ECP) of Fe3+neighboring cations. It means that the absorption feature can be used as an indicator of ferric iron in oxidized and hydrated low-Fe compounds on the surface of asteroids and other atmosphereless celestial bodies. Moreover, our measurements showed that the mechanism of light absorption is partially or completely blocked in the case of intermediate to high iron contents. Therefore, the method cannot probably be used for quantitative estimation of Fe3+ content on the bodies. Based on laboratory study of the analog samples, we conclude that spectral characteristics of Adeona, Interamnia, and Nina correspond to a mixture of CI-CM-chondrites and hydrated silicates, oxides and/or hydroxides. Spectral signs of sublimation activity on Adeona, Interamnia, and Nina at minimal heliocentric distances are likely discovered in the short-wavelength range (∼0.4-0.6 μm). It is suggested that such cometary-like activity at the highest surface temperatures is a frequent phenomenon for C and close type asteroids including considerable amounts of ices beneath the surface. A usual way of origin of a temporal coma of ice particles around a primitive asteroid is excavated fresh ice at recent impuct event(s).

The obtained reflectance spectra of two NEAs, (330825) 2008 XE3 and 2012 QG42, are predominantly featureless and could be attributed to S(C) and S(B)-type bodies, respectively. We discuss reasons why weak spectral features seen in reflectance spectra of the main-belt asteroids are not observed in those of NEAs.

Reference
Busarev VV, Barabanov SI, Rusakov VS, Puzin VB, Kravtsov VV (2015) Spectrophotometry of (32) Pomona, (145) Adeona, (704) Interamnia, (779) Nina, (330825) 2008 XE3, and 2012 QG42 and laboratory study of possible analog samples. Icarus (in Press)
Linkt to Article [doi:10.1016/j.icarus.2015.08.001]
Copyright Elsevier