^1,2Michael A. Antonelli, ²Sang-Tae Kim, ¹Marc Peters, ³Jabrane Labidi, ³Pierre Cartigny, ¹Richard J. Walker, ⁴James R. Lyons, ¹Joost Hoek, ^1,5James Farquhar
¹Department of Geology, University of Maryland, College Park, MD 20742;
²School of Geography and Earth Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada;
³Laboratoire de Géochimie des Isotopes Stables, Institut de Physique du Globe de Paris, UMR 7154 CNRS, Universite Paris Denis-Diderot, Sorbonne Paris Cite, 75005 Paris, France;
⁴School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287; and
⁵Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742

Achondrite meteorites have anomalous enrichments in 33S, relative to chondrites, which have been attributed to photochemistry in the solar nebula. However, the putative photochemical reactions remain elusive, and predicted accompanying 33S depletions have not previously been found, which could indicate an erroneous assumption regarding the origins of the 33S anomalies, or of the bulk solar system S-isotope composition. Here, we report well-resolved anomalous 33S depletions in IIIF iron meteorites (<−0.02 per mil), and 33S enrichments in other magmatic iron meteorite groups. The 33S depletions support the idea that differentiated planetesimals inherited sulfur that was photochemically derived from gases in the early inner solar system (<∼2 AU), and that bulk inner solar system S-isotope composition was chondritic (consistent with IAB iron meteorites, Earth, Moon, and Mars). The range of mass-independent sulfur isotope compositions may reflect spatial or temporal changes influenced by photochemical processes. A tentative correlation between S isotopes and Hf-W core segregation ages suggests that the two systems may be influenced by common factors, such as nebular location and volatile content.

Reference
Antonelli MA, Kim S-T, Peters M, Labidi J, Cartigny P, Walker RJ, Lyons JR, Hoek J, Farquhar J (2014) Early inner solar system origin for anomalous sulfur isotopes in differentiated protoplanets. Proceedings of the National Academy of Sciences 111, 17749-17754
Link to Article [doi:10.1073/pnas.1418907111]

¹Dennis Harries, ¹Falko Langenhorst
¹Analytical Mineralogy of Micro- and Nanostructures, Institute of Geoscience, Friedrich Schiller University Jena, Carl-Zeiss-Promenade 10, 07745 Jena,Germany

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Reference
Harries D, Langenhorst F (2014) The mineralogy and space weathering of a regolith grain from 25143 Itokawa and the possibility of annealed solar wind damage. Earth, Planets and Space 2014, 66:163
Link to Article [doi:10.1186/s40623-014-0163-1]

¹ A. Kereszturi, ²I. Gyollai, ³M. Szabó
¹Konkoly Thege Miklos Astronomical Institute, Research Center for Astronomy and Earth Sciences, H-1121 Budapest, Konkoly Thege Miklos 15-17Hungary
²Department of Lithospheric Research, University of Vienna, A-1091, Althanstrasse 14., Vienna, Austria
³Institute of Geological and Geochemical Research, Research Center for Astronomy and Earth Sciences, H-1112 Budapest, 45 Budaörsi street

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Reference
Kereszturi A, Gyollai I, Szabó M (2014) Case study of chondrule alteration with IR spectroscopy in NWA 2086 CV3 Meteorite. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2014.12.015]

^1,2S. Fornasier, ^1,3I.N. Belskaya, ¹D. Perna
¹LESIA, Observatoire de Paris, CNRS, UPMC Univ Paris 06, Univ. Paris Diderot, 5 Place J. Janssen, 92195 Meudon Pricipal Cedex, France
²Univ. Paris Diderot, Sorbonne Paris Cité, 4 rue Elsa Morante, 75205 Paris Cedex 13
³Astronomical Observatory of Kharkiv National University, 35 Sumska str., 61022 Kharkiv, Ukraine Submitted to Icarus: September 2014

In this paper we present the results on the polarimetric and spectroscopic observations of the Potentially Hazardous Asteroid (214869) 2007 PA8 obtained during its favorable apparition in October-November 2012, when it approached the Earth at the minimal distance of 0.043 AU. Polarimetry was carried out at the NOT in the B, V, R, and I bands covering both low (12-23°) and large phase angles (88-99°). Spectroscopy in the visible and near infrared range was obtained at the TNG telescope.

The spectrum of 2007 PA8 shows silicates absorption features and a behavior consistent with a Q-type classification. The olivine and pyroxene BI band is centered at 0.9578±0.0042 μm, with a band depth of 16.5%, the BII band is centered at 1.95±0.01 μm, and it has a band depth of about 3.9%. The 2007 PA8 spectral parameters are consistent with those of L chondrites. Also the spectral comparison with meteorites gives the L-type chondrites, and L6 in particular, as best match.

The NEA (214869) 2007 PA8 is the forth moderate albedo asteroid and the first Q-type asteroid for which the value of the polarization maximum is determined. The inversion angle of the polarization curve in the V filter is 19.0±1.1°, the corresponding slope parameter (h ) is of 0.078±0.010%/°, the maximum value of polarization is 5.99±0.16%, and the extreme value of negative polarization is estimated to be lower than -0.52%. Using the polarimetric slope we derive a geometric albedo of 0.29±0.08 in the V band, that gives an estimated diameter of 1.4±0.2 km, assuming an absolute HvHv magnitude of 16.2 mag. We find a strong dependence of the polarization in the B, V, R, and I bands with wavelength, and the polarimetric albedo in the four bands is strongly correlated with the asteroid’s spectrum. The 2007 PA8 polarimetric properties resemble those of other 2 NEAs, 1566 Icarus and 25143 Itokawa, which are both S(IV)/Q type.

Our spectral and polarimetric analysis indicate that 2007 PA8 has a young and fresh surface almost unweathered, similar to L-type chondrites. These results, together with dynamical simulations made by Nedelcu et al., 2014 and Nesvorny et al., 2009, indicate that 2007 PA8 may be a member of the Gefion family recently ejected from the 5:2 resonance and a potential source of L chondrites.

Reference
Fornasier S, Belskaya IN, Perna D (2014) The potentially hazardous asteroid (214869) 2007 PA8: an unweathered L chondrite analogue surface. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2014.12.015]

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¹Joke Belza, ^1,2Steven Goderis, ³Jan Smit, ²Frank Vanhaecke, ⁴Kitty Baert, ⁴Herman Terryn, ¹Philippe Claeys
¹Department of Analytical Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, BE-1050 Brussels, Belgium
²Department of Analytical Chemistry, Universiteit Gent, Krijgslaan 281-S12, BE-9000 Ghent, Belgium
³Department of Sedimentology, Vrije Universiteit Amsterdam, de Boelelaan 1085, 1081HV Amsterdam, Netherlands
⁴Department of Electrochemical and Surface Engineering, Vrije Universiteit Brussel, Pleinlaan 2, BE-1050 Brussels, Belgium

Using laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS), we have conducted spatially resolved trace element analysis on fresh, unaltered microtektite glasses linked to the Cretaceous-Paleogene (K-Pg) boundary Chicxulub crater and on their surrounding alteration phases. This unique approach offers the opportunity to study in situ and at high spatial resolution both the mixing of different target lithologies and the variation of the major and trace element budget during the alteration process. In addition, two-dimensional element distribution maps reveal important geochemical information beyond the capabilities of single spot laser drilling. Glasses from two localities in opposite quadrants from the source crater were studied. At the Beloc locality (Haiti), the glass population is dominated by the presence of yellow high-Ca glass and black andesitic glass formed by admixture of carbonate/dolomite/anhydrite platform lithologies with crystalline basement. These glasses alter according to the well-established hydration-palagonitisation model postulated for mafic volcanic glasses. REEs become progressively leached from the glass to below the detection limit for the applied spot size, while immobile Zr, Hf, Nb, and Ta passively accumulate in the process exhibiting both inter-element ratios and absolute concentrations similar to those for the original glass. In contrast, The Arroyo El Mimbral locality (NE Mexico) is characterized by abundant green glass fragments high in Si, Al and alkalis, and low in Mg, Ca, Fe. Low Si black glass is less abundant though similar in composition to the black glass variety at Beloc. The alteration pattern of high-Si, Al green glass at the Mimbral locality is more complex, including numerous competing reaction processes (ion-exchange, hydration, dissolution, and secondary mineral precipitation) generally controlled by the pH and composition of the surrounding fluid. All green, high-Si, Al glasses are hydrated and variably enriched in Sr, Ba, and Cs, indicating preferred adsorption from seawater during hydration. Despite the onset of ion-exchange reactions, which only seem to have affected the alkalis, the trace element composition of the green high-Si, Al glass is still largely representative of the original melt composition. Refining the geochemical signature of (altered) melt lithologies may advance our current understanding of glass stability in the natural environment and provide insight into the origin and emplacement of ejecta material during crater formation.

Reference
Belza J, Goderis S, Smit J, Vanhaecke F, Baert K, Terryn H, Claeys P (2014) High spatial resolution geochemistry and textural characteristics of ‘microtektite’ glass spherules in proximal Cretaceous-Paleogene sections: insights into glass alteration patterns and precursor melt lithologies. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2014.12.013]

Copyright Elsevier