^1,2M.M.M. Meier, ³A. Reufer, ²R. Wieler
¹Centre de Recherches Pétrographiques et Géochimiques, CNRS Nancy, France
²Department of Earth Sciences, ETH Zurich, Switzerland
³School of Earth & Space Exploration, Arizona State University, AZ 85287-6004, USA

Knowing the isotopic composition of Theia, the proto-planet which collided with the Earth in the Giant Impact that formed the Moon, could provide interesting insights on the state of homogenization of the inner Solar System at the late stages of terrestrial planet formation. We use the known isotopic and modeled chemical compositions of the bulk silicate mantles of Earth and Moon and combine them with different Giant Impact models, to calculate the possible ranges of isotopic composition of Theia in O, Si, Ti, Cr, Zr and W in each model. We compare these ranges to the isotopic composition of carbonaceous chondrites, Mars, and other Solar System materials. In the absence of post-impact isotopic re-equilibration, the recently proposed high angular momentum models of the Giant Impact (“impact-fission”, Cúk, M., Stewart, S.T. [2012]. Science 338, 1047; and “merger”, Canup, R.M. [2012]. Science 338, 1052) allow – by a narrow margin – for a Theia similar to CI-chondrites, and Mars. The “hit-and-run” model (Reufer, A., Meier, M.M.M., Benz, W., Wieler, R. [2012]. Icarus 221, 296–299) allows for a Theia similar to enstatite-chondrites and other Earth-like materials. If the Earth and Moon inherited their different mantle FeO contents from the bulk mantles of the proto-Earth and Theia, the high angular momentum models cannot explain the observed difference. However, both the hit-and-run as well as the classical or “canonical” Giant Impact model naturally explain this difference as the consequence of a simple mixture of two mantles with different FeO. Therefore, the simplest way to reconcile the isotopic similarity, and FeO dissimilarity, of Earth and Moon is a Theia with an Earth-like isotopic composition and a higher (∼20%) mantle FeO content.

Reference
Meier MMM, Reufer A, Wieler R (2014) On the origin and composition of Theia: Constraints from new models of the Giant Impact. Icarus 242, 316–328 Link to Article [DOI: 10.1016/j.icarus.2014.08.003]

Copyright Elsevier

¹Alian Wang, ¹Randy L. Korotev, ¹Bradley L. Jolliff, ²Zongcheng Ling
¹Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, USA
²School of Space Science and Physics, Shandong University, Weihai Campus, China

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Reference
Wang A, Korotev RL, Jolliff BL,Ling Z (2014) Raman imaging of extraterrestrial Materials. Planetary and Space Science (in Press)
Link to Article [DOI: 10.1016/j.pss.2014.10.005]

^1,2Michael N. Mautner
¹Department of Chemistry, Virginia Commonwealth University, Richmond, VA 23284-2006, USA
²Soil and Physical Sciences Department, Lincoln University, Lincoln, New Zealand

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Reference
Mautner MN (2014) In situ biological Resources: Soluble Nutrients and Electrolytes in carbonaceous asteroids/meteorites. Implications for astroecology and space populations. Planetary and Space Science (in Press)
Link to Article [DOI: 10.1016/j.pss.2014.10.001]

¹J. Mortimer, ¹A.B. Verchovsky, ^1,2M. Anand, ¹I. Gilmour,¹C.T. Pillinger,
¹Planetary and Space Sciences, Department of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
²Department of Earth Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK

Simultaneous static-mode mass spectrometric measurements of nitrogen, carbon, helium, neon, and argon extracted from the same aliquot of sample by high-resolution stepped combustion have been made for a suite of six lunar basalts.
Collecting abundance and isotopic data for several elements simultaneously from the same sample aliquot enables more detailed identification of different volatile components present in the basalts by comparing release patterns for volatiles across a range of temperature steps. This approach has yielded new data, from which new insights can be gained regarding the indigenous volatile inventory of the Moon.
By taking into account N and C data for mid-temperature steps, unaffected by terrestrial contamination or cosmogenic additions, it is possible to determine the indigenous N and C signatures of the lunar basalts. With an average δ15N value of around +0.35 ‰, the indigenous N component seen in these samples is similar within error to other (albeit limited in number) isotopic measurements of indigenous lunar N. Average C/N ratios for indigenous volatiles in these six basalt samples are much lower than those of the terrestrial depleted mantle, or bulk silicate Earth, possibly suggesting much less C in the lunar interior, relative to N, than on Earth.
Cosmogenic isotopes in these samples are well-correlated with published sample exposure ages, and record the rate of in situ production of spallogenic volatiles within material on the lunar surface.

Reference
Mortimer J, Verchovsky AB, M. Anand M, Gilmour I, Pillinger CT (2014) IcaruSimultaneous analysis of abundance and isotopic composition of nitrogen, carbon, and noble gases in lunar basalts: insights into interior and surface processes on the Moon. Icarus (in Press)
Link to Article [DOI: 10.1016/j.icarus.2014.10.006]

Copyright Elsevier

¹Subrata Chakraborty, ²B. H. Muskatel, ¹Teresa L. Jackson, ³Musahid Ahmed, ^2,4R. D. Levine,¹Mark H. Thiemens
¹Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0356
²The Fritz Haber Research Center for Molecular Dynamics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
³Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
⁴Department of Chemistry and Biochemistry, Crump Institute for Molecular Imaging, and Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095

Nitrogen isotopic distributions in the solar system extend across an enormous range, from −400‰, in the solar wind and Jovian atmosphere, to about 5,000‰ in organic matter in carbonaceous chondrites. Distributions such as these require complex processing of nitrogen reservoirs and extraordinary isotope effects. While theoretical models invoke ion-neutral exchange reactions outside the protoplanetary disk and photochemical self-shielding on the disk surface to explain the variations, there are no experiments to substantiate these models. Experimental results of N2 photolysis at vacuum UV wavelengths in the presence of hydrogen are presented here, which show a wide range of enriched δ15N values from 648‰ to 13,412‰ in product NH3, depending upon photodissociation wavelength. The measured enrichment range in photodissociation of N2, plausibly explains the range of δ15N in extraterrestrial materials. This study suggests the importance of photochemical processing of the nitrogen reservoirs within the solar nebula.

Reference
Chakraborty S, Muskatel BH, Jackson TL, Ahmed M, Levine RD, Thiemens MH (2014) Massive isotopic effect in vacuum UV photodissociation of N2 and implications for meteorite data. Proceedings of the National Academy of Sciences 111, 41
Link to Article [doi: 10.1073/pnas.1410440111]

¹D. Ray, ²S. Misra
¹PLANEX, Physical Research Laboratory, Ahmedabad, 380009, India
²Discipline of Geological Sciences, SAEES, University of KwaZulu-Natal, Durban, 4000, South Africa

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Reference
Ray D, Misra S (2014) Contrasting Aerodynamic Morphology and Geochemistry of Impact Spherules from Lonar Crater, India: Some Insights into Their Cooling History. Earth, Moon and Planets (in Press)
Link to Article [10.1007/s11038-014-9451-9]

¹Pavel Spurný, ^2,3Jakub Haloda, ¹Jiří Borovička, ¹Lukáš Shrbený,²Patricie Halodová
¹Astronomical Institute, Academy of Sciences, 25165 Ondřejov, Czech Republic
²Czech Geological Survey, Geologická 6, 15200 Praha 5, Czech Republic
³Oxford Instruments NanoAnalysis, Halifax Road, High Wycombe, HP12 3SE, UK

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Reference
Spurný P, Haloda J, Borovička J, Shrbený L, Halodová P (2014) Reanalysis of the Benešov bolide and recovery of polymict breccia meteorites – old mystery solved after 20 years. Astronomy&Astrophysics 570.
Link to Article [http://dx.doi.org/10.1051/0004-6361/201424308]

¹W. H. Farrand,²J. F. Bell III,³J. R. Johnson,⁴M. S. Rice, ⁵B. L. Jolliff,⁵R. E. Arvidson
¹Space Science Institute, Boulder, Colorado, USA
²Arizona State University, School of Earth and Space Exploration, Tempe, AZ, USA
³Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA
⁴Western Washington University, Bellingham, WA, USA
⁵Washington University, St. Louis, MO, USA

The Opportunity rover’s exploration of the portion of the rim of Endeavour crater known as Cape York included examination of the sulfate-bearing Grasberg formation and the Matijevic Hill region. Multispectral visible and near infrared (VNIR) Pancam observations were used to characterize reflectance properties of rock units. Using spectral endmember detection and classification approaches including a principal components/n-dimensional visualization, automatic sequential maximum angle convex cone method, and classification through hierarchical clustering, six main spectral classes of rock surfaces were identified: light-toned veins, Grasberg fm., the smectite-bearing Matijevic formation, the hematitic “blueberry” spherules, resistant spherules within the Matijevic fm. dubbed “newberries”, and the Shoemaker formation impact breccia. Some of these could be divided into spectral sub-classes. There were three types of veins: veins in the bench unit of Cape York, thinner veins in the Matijevic fm., and boxwork pattern-forming veins. The bench unit veins had higher 535 nm band depths than the other two vein sub-classes and a steeper 934 to 1009 nm slope. The Grasberg fm. has VNIR spectral features that are interpreted to indicate higher fractions of red hematite than in the sulfate-bearing Burns Fm. The Matijevic fm. includes both light-toned, fine-grained matrix and dark-toned veneers. The latter has a weak NIR absorption band centered near 950 nm consistent with nontronite. Observations of Rock Abrasion Tool brushed and ground newberries indicated that cuttings from the RAT grind had a longer wavelength reflectance maximum and deeper 535 nm band depth, consistent with more oxidized materials. Greater oxidation of cementing materials in the newberries is consistent with a diagenetic concretion origin.

Reference
Farrand WH, Bell III JF, Johnson JR, Rice MS, Jolliff BL, Arvidson RE (2014) Observations of Rock Spectral Classes by the Opportunity Rover’s Pancam on northern Cape York and on Matijevic Hill, Endeavour Crater, Mars. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004641]

Published by arrangement with John Wiley&Sons

¹Travis J. Tenner,¹Daisuke Nakashima,¹Takayuki Ushikubo,¹Noriko T. Kita,^2,3Michael K. Weisberg
¹WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, WI 53706, USA
²Kingsborough Community College and Graduate Center, The City University of New York, 2001 Oriental Boulevard, Brooklyn, NY 11235-2398, USA
³American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192, USA

We present detailed electron microprobe analyses and oxygen three-isotope measurements by high precision secondary ion mass spectrometry on 45 type I (FeO-poor) chondrules/fragments and 3 type II (FeO-rich) chondrule fragments from Meteorite Hills 00426 and Queen Alexandra Range 99177, two of the most primitive CR3 chondrites. Type I chondrules/fragments have Mg#’s (defined as the Mg# of constituent olivine and/or low-Ca pyroxene) ranging from 94.2 to 99.2; type II chondrule fragments have Mg#’s of 53–63. Oxygen three-isotope measurements plot on the slope ∼1 primitive chondrule mineral (PCM) line. Within chondrules, Δ17O (=δ17O–0.52 × δ18O) values of coexisting olivine, pyroxene, and plagioclase are homogeneous, with propagated uncertainties of 0.3‰. This indicates each phase crystallized from the final chondrule melt, and that efficient oxygen isotope exchange occurred between ambient gas and chondrule melt. Among type I chondrules there is a well-defined increase in Δ17O, from –5.9‰ to ∼−1‰, as Mg#’s decrease from 99.2 to ∼96; type II chondrule fragments are comparatively 16O-poor (Δ17O: ∼0.2–0.6‰). The relationship between Mg# and Δ17O among type I chondrules confirms that addition of a 16O-poor oxidizing agent to the highest Mg# chondrule precursors resulted in forming lower Mg# CR chondrules. Using aspects of existing equilibrium condensation models and a mass balance we estimate that type I CR chondrules formed at dust enrichments of 100–200×, from dusts with 0–0.8 times the atomic abundance of ice, relative to CI dust. The type II chondrule fragments are predicted to have formed at CI dust enrichments near 2500×.

Reference
Tenner TJ, Nakashima D, Ushikubo T, Kita NT, Weisberg MK (2014) Oxygen isotope ratios of FeO-poor chondrules in CR3 chondrites: Influence of dust enrichment and H2O during chondrule Formation. Geochimica et Cosmochimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2014.09.025]

Copyright Elsevier

¹M. Nagasawa, ²K. K. Tanaka, ²H. Tanaka, ³T. Nakamoto, ⁴H. Miura, ⁵T. Yamamoto
¹Interactive Research Center of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
²Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo 060-0819, Japan
³Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
⁴Graduate School of Natural Sciences, Nagoya City University, 1 Yamanohata, Mizuho-cho, Mizuho-ku, Nagoya 467-8501, Japan
⁵Center for Planetary Science, Kobe University, 7-1-48 Minamimachi, Minatojima, Chuo-ku, Kobe 650-0047, Japan

It is proposed that planetesimals perturbed by Jovian mean-motion resonances are the source of shock waves that form chondrules. It is considered that this shock-induced chondrule formation requires the velocity of the planetesimal relative to the gas disk to be on the order of gsim 7 km s–1 at 1 AU. In previous studies on planetesimal excitation, the effects of Jovian mean-motion resonance together with the gas drag were investigated, but the velocities obtained were at most 8 km s–1 in the asteroid belt, which is insufficient to account for the ubiquitous existence of chondrules. In this paper, we reexamine the effect of Jovian resonances and take into account the secular resonance in the asteroid belt caused by the gravity of the gas disk. We find that the velocities relative to the gas disk of planetesimals a few hundred kilometers in size exceed 12 km s–1, and that this is achieved around the 3:1 mean-motion resonance. The heating region is restricted to a relatively narrowband between 1.5 AU and 3.5 AU. Our results suggest that chondrules were produced effectively in the asteroid region after Jovian formation. We also find that many planetesimals are scattered far beyond Neptune. Our findings can explain the presence of crystalline silicate in comets if the scattered planetesimals include silicate dust processed by shock heating.

Reference
Nagasawa M, Tanaka KK, Tanaka H, Nakamoto T, Miura H, Yamamoto T (2014) Revisiting Jovian-resonance Induced Chondrule Formation. The Astrophysical Journal Letters 794, 1, L7
Link to Article [doi:10.1088/2041-8205/794/1/L7]