¹K. Righter,²M. A. Cosca,²L. E. Morgan
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12692]
¹Mailcode XI2, NASA Johnson Space Center, Houston, Texas, USA
¹U.S. Geological Survey, Denver Federal Center, Denver, Colorado, USA
Published by arrangement with John Wiley & Sons

The hornblende- and biotite-bearing R chondrite LAP 04840 is a rare kind of meteorite possibly containing outer solar system water stored during metamorphism or postshock annealing deep within an asteroid. Because little is known regarding its age and origin, we determined 40Ar/39Ar ages on hornblende-rich separates of the meteorite, and obtained plateau ages of 4340(±40) to 4380(±30) Ma. These well-defined plateau ages, coupled with evidence for postshock annealing, indicate this meteorite records an ancient shock event and subsequent annealing. The age of 4340–4380 Ma (or 4.34–4.38 Ga) for this and other previously dated R chondrites is much older than most impact events recorded by ordinary chondrites and points to an ancient event or events that predated the late heavy bombardment that is recorded in so many meteorites and lunar samples.

¹Yang Liu, ²Chi Ma, ²John R. Beckett, ¹Yang Chen, ²Yunbin Guan
Earth and Planetary Science Letters (in Press) Link to Article [doi:10.1016/j.epsl.2016.06.041]
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
²Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
Copyright Elsevier

Paired martian breccia meteorites, Northwest Africa (NWA) 7034 and 7533, are the first martian rocks found to contain rare-earth-element (REE) phosphates and silicates. The most common occurrence is as clusters of anhedral monazite-(Ce) inclusions in apatite. Occasionally, zoned, irregular merrillite inclusions are also present in apatite. Monazite-bearing apatite is sometimes associated with alkali-feldspar and Fe-oxide. Apatite near merrillite and monazite generally contains more F and OH (F-rich region) than the main chlorapatite host and forms irregular boundaries with the main host. Locally, the composition of F-rich regions can reach pure fluorapatite. The chlorapatite hosts are similar in composition to isolated apatite without monazite inclusions, and to euhedral apatite in lithic clasts. The U–Th-total Pb ages of monazite in three apatite are View the MathML source1.0±0.4Ga (2σ ), View the MathML source1.1±0.5Ga (2σ ), and View the MathML source2.8±0.7Ga (2σ), confirming a martian origin. The texture and composition of monazite inclusions are mostly consistent with their formation by the dissolution of apatite and/or merrillite by fluid at elevated temperatures (>100 °C).

In NWA 7034, we observed a monazite-chevkinite-perrierite-bearing benmoreite or trachyandesite clast. Anhedral monazite and chevkinite-perrierite grains occur in a matrix of sub-micrometer REE-phases and silicates inside the clast. Monazite-(Ce) and -(Nd) and chevkinite-perrierite-(Ce) and -(Nd) display unusual La and Ce depletion relative to Sm and Nd. In addition, one xenotime-(Y)-bearing pyrite-ilmenite-zircon clast with small amounts of feldspar and augite occurs in NWA 7034. One xenotime crystal was observed at the edge of an altered zircon grain, and a cluster of xenotime crystals resides in a mixture of alteration materials. Pyrite, ilmenite, and zircon in this clast are all highly altered, zircon being the most likely source of Y and HREE now present in xenotime. The association of xenotime with zircon, low U and Th contents, and the low Yb content relative to Gd and Dy in xenotime suggest the possible formation of xenotime as a byproduct of fluid–zircon reactions.

On the basis of relatively fresh apatite grains and lithic clasts in the same samples, we propose that the fluid–rock/mineral reactions occurred in the source rocks before their inclusion in NWA 7034 and 7533. Additionally, monazite-bearing apatite and REE-mineral-bearing clasts are possibly derived from different crustal origins. Thus, our results imply the wide-occurrence of hydrothermal fluids in the martian crust at 1 Ga or older, which were probably induced by impacts or large igneous intrusions.

¹Ch. Helling, ¹G. Lee, ²I. Dobbs-Dixon, ³N. Mayne, ³D. S. Amundsen, ^1,4J. Khaimova, ¹A. A. Unger, ³J. Manners, ⁵D. Acreman,⁵C. Smith
Monthly Notices of the Royal Astronomical Society 460, 855-883 Link to Article [doi: 10.1093/mnras/stw662]
¹SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
²Department of Physics, NYU Abu Dhabi, PO Box 129188, Abu Dhabi, UAE
³Physics and Astronomy, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QL, UK
⁴Brooklyn College, City University of New York, Brooklyn, NY, USA
⁵Met Office, Exeter EX1 3PB, UK

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

^1,2Marianna Mészáros et al. (>10)*
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12693]
¹Space Research and Planetary Sciences, University of Bern, Bern, Switzerland
²Natural History Museum Bern, Bern, Switzerland
*Find the extensive, full author and affiliation list on the publishers website
Published by arrangement with John Wiley & Sons

Abar al’ Uj (AaU) 012 is a clast-rich, vesicular impact-melt (IM) breccia, composed of lithic and mineral clasts set in a very fine-grained and well-crystallized matrix. It is a typical feldspathic lunar meteorite, most likely originating from the lunar farside. Bulk composition (31.0 wt% Al2O3, 3.85 wt% FeO) is close to the mean of feldspathic lunar meteorites and Apollo FAN-suite rocks. The low concentration of incompatible trace elements (0.39 ppm Th, 0.13 ppm U) reflects the absence of a significant KREEP component. Plagioclase is highly anorthitic with a mean of An96.9Ab3.0Or0.1. Bulk rock Mg# is 63 and molar FeO/MnO is 76. The terrestrial age of the meteorite is 33.4 ± 5.2 kyr. AaU 012 contains a ~1.4 × 1.5 mm2 exotic clast different from the lithic clast population which is dominated by clasts of anorthosite breccias. Bulk composition and presence of relatively large vesicles indicate that the clast was most probably formed by an impact into a precursor having nonmare igneous origin most likely related to the rare alkali-suite rocks. The IM clast is mainly composed of clinopyroxenes, contains a significant amount of cristobalite (9.0 vol%), and has a microcrystalline mesostasis. Although the clast shows similarities in texture and modal mineral abundances with some Apollo pigeonite basalts, it has lower FeO and higher SiO2 than any mare basalt. It also has higher FeO and lower Al2O3 than rocks from the FAN- or Mg-suite. Its lower Mg# (59) compared to Mg-suite rocks also excludes a relationship with these types of lunar material.

¹Andrew Steele,²Francis M. McCubbin,¹Marc D. Fries
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12670]
¹Geophysical Laboratory, Carnegie Institution of Washington, NW Washington, District of Columbia, USA
²NASA Johnson Space Center, Houston, Texas, USA
Published by arrangement with John Wiley & Sons

This review is intended to summarize the current observations of reduced carbon in Martian meteorites, differentiating between terrestrial contamination and carbon that is indigenous to Mars. Indeed, the identification of Martian organic matter is among the highest priority targets for robotic spacecraft missions in the next decade, including the Mars Science Laboratory and Mars 2020. Organic carbon compounds are essential building blocks of terrestrial life, so the occurrence and origin (biotic or abiotic) of organic compounds on Mars is of great significance; however, not all forms of reduced carbon are conducive to biological systems. This paper discusses the significance of reduced organic carbon (including methane) in Martian geological and astrobiological systems. Specifically, it summarizes current thinking on the nature, sources, and sinks of Martian organic carbon, a key component to Martian habitability. Based on this compilation, reduced organic carbon on Mars, including detections of methane in the Martian atmosphere, is best described through a combination of abiotic organic synthesis on Mars and infall of extraterrestrial carbonaceous material. Although conclusive signs of Martian life have yet to be revealed, we have developed a strategy for life detection on Mars that can be utilized in future life-detection studies.

¹Kai Wünnemann,^1,2Meng-Hua Zhu,¹Dieter Stöffler
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12710]
¹Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
²Space Science Institute, Macau University of Science and Technology, Taipa, Macau
Published by arrangement with John Wiley & Sons

We investigated the ejection mechanics by a complementary approach of cratering experiments, including the microscopic analysis of material sampled from these experiments, and 2-D numerical modeling of vertical impacts. The study is based on cratering experiments in quartz sand targets performed at the NASA Ames Vertical Gun Range. In these experiments, the preimpact location in the target and the final position of ejecta was determined by using color-coded sand and a catcher system for the ejecta. The results were compared with numerical simulations of the cratering and ejection process to validate the iSALE shock physics code. In turn the models provide further details on the ejection velocities and angles. We quantify the general assumption that ejecta thickness decreases with distance according to a power-law and that the relative proportion of shocked material in the ejecta increase with distance. We distinguish three types of shock metamorphic particles (1) melt particles, (2) shock lithified aggregates, and (3) shock-comminuted grains. The agreement between experiment and model was excellent, which provides confidence that the models can predict ejection angles, velocities, and the degree of shock loading of material expelled from a crater accurately if impact parameters such as impact velocity, impactor size, and gravity are varied beyond the experimental limitations. This study is relevant for a quantitative assessment of impact gardening on planetary surfaces and the evolution of regolith layers on atmosphereless bodies.

^1,2Louise Alexander,^2,3Joshua F. Snape,⁴Katherine H. Joy,^1,2Hilary Downes,^1,2Ian A. Crawford
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12689]
¹Department of Earth and Planetary Science, Birkbeck College, University of London, London, UK
²The Centre for Planetary Sciences at UCL-Birkbeck, London, UK
³Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
⁴School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
Published by arrangement with John Wiley & Sons

¹Rebecca Winkler,¹Michael H. Poelchau,²Stefan Moser,¹Thomas Kenkmann
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12694]
¹Institute of Earth and Environmental Sciences—Geology, Albert-Ludwigs-Universität Freiburg (ALU), Freiburg, Germany
²Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach Institut, EMI, Efringen-Kirchen, Germany
Published by arrangement with John Wiley & Sons

Hypervelocity impact experiments on porous tuff targets were carried out to determine the effect of porosity on deformation mechanisms in the crater’s subsurface. Blocks of Weibern Tuff with about 43% porosity were impacted by 2.5 mm and 12.0 mm diameter steel spheres with velocities between 4.8 km s−1 and 5.6 km s−1. The postimpact subsurface damage was quantified with computer tomography as well as with meso- and microscale analyses of the bisected crater subsurface. The intensity and style of deformation in mineral clasts and the tuff matrix were mapped and their decay with subsurface depth was determined. Subsurface deformation styles include pore space compaction, clast rotation, as well as microfracture formation. Evaluation of the deformation indicates near-surface energy coupling at a calculated depth of burial of ~2 projectile diameters (dp), which is in conflict with the crater shape, which displays a deep, central penetration tube. Subsurface damage extends to ~2 dp beneath the crater floor in the experiments with 2.5 mm projectiles and increases to ~3 dp for 12 mm projectiles. Based on overprinting relationships and the geometrical orientation of deformation features, a sequence of subsurface deformation events was derived (1) matrix compaction, (2) intragranular crack formation in clasts, (3) deformation band formation in the compacted matrix, (4) tensile fracturing.

¹Carles E. Moyano-Cambero,¹Josep M. Trigo-Rodriguez,²Jordi Llorca,³Sonia Fornasier,³Maria A. Barucci,⁴Albert Rimola
Meteoritics & Planetary Science (in Press)  Link to Article [DOI: 10.1111/maps.12703]
¹Institut de Ciències de l’Espai (CSIC-IEEC), Campus UAB, Barcelona, Spain
²Institut de Tècniques Energètiques i Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, ETSEIB, Barcelona, Spain
³LESIA, Observatoire de Paris, PSL Research University, CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, UPMC Univ. Paris 06, Sorbonne Universités, Meudon Principal Cedex, France
⁴Departament de Química, Universitat Autònoma de Barcelona, Bellaterra, Spain
Published by arrangement with John Wiley & Sons

A crucial topic in planetology research is establishing links between primitive meteorites and their parent asteroids. In this study, we investigate the feasibility of a connection between asteroids similar to 21 Lutetia, encountered by the Rosetta mission in July 2010, and the CH3 carbonaceous chondrite Pecora Escarpment 91467 (PCA 91467). Several spectra of this meteorite were acquired in the ultraviolet to near-infrared (0.3–2.2 μm) and in the midinfrared to thermal infrared (2.5–30.0 μm or 4000 to ~333 cm−1), and they are compared here to spectra from the asteroid 21 Lutetia. There are several similarities in absorption bands and overall spectral behavior between this CH3 meteorite and 21 Lutetia. Considering also that the bulk density of Lutetia is similar to that of CH chondrites, we suggest that this asteroid could be similar, or related to, the parent body of these meteorites, if not the parent body itself. However, the apparent surface diversity of Lutetia pointed out in previous studies indicates that it could simultaneously be related to other types of chondrites. Future discovery of additional unweathered CH chondrites could provide deeper insight in the possible connection between this family of metal-rich carbonaceous chondrites and 21 Lutetia or other featureless, possibly hydrated high-albedo asteroids.

¹Lingzhi Sun, ^1,2Zongcheng Ling, ¹Jiang Zhang, ¹Bo Li, ¹Jian Chen, ¹Zhongchen Wu, ³Jianzhong Liu
Icarus (in Press) Link to Article [doi:10.1016/j.icarus.2016.07.010]
¹School of Space Science and Physics, Shandong Provincial Key Laboratory of Optical Astronomy & Solar-Terrestrial Environment, Shandong University, Weihai 264209, China
²Key Laboratory of Lunar and Deep Space Exploration, Chinese Academy of Sciences, Beijing 100012, China
³Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, China
Copyright Elsevier

Iron and optical maturity (OMAT) are two key geological marks of the Moon that closely related to its geochemical evolution and interactions between surface and space environment. We apply Partial Least Squares (PLS) regression to Chang’E-1 Imaging Interferometer (IIM) (32 bands between 480 and 960 nm) in mapping lunar global FeO and OMAT, and the FeO and OMAT values are derived based on reasonable spectral parameters (absorbance, band ratios, TiO2 and maturity sensitive parameters, etc.). After been calibrated by the FeO map from Lunar Prospector Gamma-Ray Spectrometer (LP-GRS), the global FeO map derived from PLS modeling shows a quantitatively more reasonable result consistent with previous remote sensing results (LP) as well as lunar feldspathic meteorite studies and Chang’E-3 landing site. Based on the new FeO map by Chang’E-1, we discover a compositional inhomogeneity across lunar highland regions, which has not been suggested by previous datasets (e.g., Clementine UVVIS). Furthermore, we suggest that at least part of the FeO enrichments in highlands would be caused by mixing of highland and mare materials. The IIM derived OMAT map does not suggest a dichotomy of the lunar highlands and mare regions, implying the compositional differences between those two terrains have been suppressed. We further check the maturity effect for the young mare basalts (20 wt.%) and ultrahigh-TiO2 (>10 wt.%) tend to have greater OMAT values and vary little with ages; (3) this may be due to the distinct optical maturity effects of ultramafic minerals (i.e., ultrahigh Fe and Ti) and/or the spectral blue shifts of abundant ilmenite.