J. H. Jones

KR, NASA/JSC, Houston, Texas, USA

Several controversies are associated with the age and origin of the shergottite meteorites, a suite of basaltic samples from Mars. Here, it will be argued that (1) the shergottites have a young igneous age, ≤600 Myr, (2) their parent magmas were relatively dry, (3) the range of initial isotopic compositions in shergottites is most likely due to assimilation of crustal materials by mantle-derived basaltic magmas, and (4) the intercumulus liquid compositions of shergottites such as Shergotty and Zagami are relatively well constrained.

Reference
Jones JH (2015) Various aspects of the petrogenesis of the Martian shergottite meteorites. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12421]

Published by arrangement with John Wiley & Sons

Annelies Van Hoesel^1,2, Wim Z. Hoek², Gillian M. Pennock¹, Knut Kaiser³, Oliver Plümper¹, Michal Jankowski⁴, Maartje F. Hamers¹, Norbert Schlaak⁵, Mathias Küster⁶, Alexander V. Andronikov⁷ and Martyn R. Drury¹

¹Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands
²Department of Physical Geography, Utrecht University, Utrecht, The Netherlands
³GFZ German Research Centre for Geosciences, Potsdam, Germany
⁴Department of Soil Science and Landscape Management, Nicolaus Copernicus University, Toruń, Poland
⁵State Agency for Mining, Geology and Resources Brandenburg (LBGR), Cottbus, Germany
⁶Institute of Geography and Geology, University of Greifswald, Greifswald, Germany
⁷Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA

The Younger Dryas impact hypothesis suggests that multiple airbursts or extraterrestrial impacts occurring at the end of the Allerød interstadial resulted in the Younger Dryas cold period. So far, no reproducible, diagnostic evidence has, however, been reported. Quartz grains containing planar deformation features (known as shocked quartz grains), are considered a reliable indicator for the occurrence of an extraterrestrial impact when found in a geological setting. Although alleged shocked quartz grains have been reported at a possible Allerød-Younger Dryas boundary layer in Venezuela, the identification of shocked quartz in this layer is ambiguous. To test whether shocked quartz is indeed present in the proposed impact layer, we investigated the quartz fraction of multiple Allerød-Younger Dryas boundary layers from Europe and North America, where proposed impact markers have been reported. Grains were analyzed using a combination of light and electron microscopy techniques. All samples contained a variable amount of quartz grains with (sub)planar microstructures, often tectonic deformation lamellae. A total of one quartz grain containing planar deformation features was found in our samples. This shocked quartz grain comes from the Usselo palaeosol at Geldrop Aalsterhut, the Netherlands. Scanning electron microscopy cathodoluminescence imaging and transmission electron microscopy imaging, however, show that the planar deformation features in this grain are healed and thus likely to be older than the Allerød-Younger Dryas boundary. We suggest that this grain was possibly eroded from an older crater or distal ejecta layer and later redeposited in the European sandbelt. The single shocked quartz grain at this moment thus cannot be used to support the Younger Dryas impact hypothesis.

Reference
Van Hoesel A, Hoek WZ, Pennock GM, Kaiser K, Plümper O, Jankowski M, Hamers MF, Schlaak N, Küster M, Andronikov AV and Drury MR (2015) A search for shocked quartz grains in the Allerød-Younger Dryas boundary layer. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12435]

Published by arrangement with John Wiley & Sons

Luigi Folco¹, Massimo D’Orazio¹, Agnese Fazio¹, Carole Cordier^2,3, Antonio Zeoli⁴, Matthias van Ginneken⁵ and Ahmed El-Barkooky⁶

¹Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
²Université de Grenoble Alpes, Grenoble, CEDEX 9, France
³CNRS, Istitute des Sciences de la Terre (ISTerre), Grenoble, CEDEX 9, France
⁴Museo Nazionale dell’Antartide, Università di Siena, Siena, Italy
⁵Department of Earth Science and Engineering, Imperial College, London, UK
⁶Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt

We report on the microscopic impactor debris around Kamil crater (45 m in diameter, Egypt) collected during our 2010 geophysical expedition. The hypervelocity impact of Gebel Kamil (Ni-rich ataxite) on a sandstone target produced a downrange ejecta curtain of microscopic impactor debris due SE–SW of the crater (extending ~300,000 m2, up to ~400 m from the crater), in agreement with previous determination of the impactor trajectory. The microscopic impactor debris include vesicular masses, spherules, and coatings of dark impact melt glass which is a mixture of impactor and target materials (Si-, Fe-, and Al-rich glass), plus Fe-Ni oxide spherules and mini shrapnel, documenting that these products can be found in craters as small as few tens of meters in diameter. The estimated mass of the microscopic impactor debris (20 t, likely 50–60 t).

Reference
Luigi Folco L, D’Orazio M, Fazio A, Cordier C, Zeoli A, van Ginneken M and El-Barkooky A (2015) Microscopic impactor debris in the soil around Kamil crater (Egypt): Inventory, distribution, total mass, and implications for the impact scenario. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12427]

Published by arrangement with John Wiley & Sons

M. Alvaro1^1,†, M. C. Domeneghetti², A. M. Fioretti³, F. Cámara^4,5 and L. Marinangeli⁶

¹Dipartimento di Geoscienze, Università degli Studi di Padova, Padova, Italy
²Dipartimento di Scienze della Terra e dell’Ambiente, Università degli Studi di Pavia, Pavia, Italy
³Instituto di Geoscienze e Georisorse CNR, UOS di Padova, Padova, Italy
⁴Dipartimento di Scienze della Terra, Università di Torino, Torino, Italy
⁵CrisDi, Interdepartmental Centre for the Research and Development of Crystallography, Torino, Italy
⁶International Research School of Planetary Sciences, Università G. d’Annunzio, Chieti, Italy
^†Dipartimento di Scienze della Terra e dell’Ambiebnte, Università degli Studi di Pavia, Pavia, Italy

Recently it has been shown that the relatively low closure temperature (Tc) of 500 (100)°C calculated for augite from Miller Range nakhlite (MIL 03346,13) using the available geothermometers would correspond to a slow cooling rate inconsistent with the petrologic evidence for an origin from a fast-cooled lava flow. Moreover, previous annealing experiments combined with HR-SC-XRD on an augite crystal from MIL 03346 clearly showed that at 600 °C, the Fe2+-Mg degree of order remained unchanged, thus suggesting that the actual Tc is close to this temperature. In order to clarify this discrepancy, we undertook an ex situ annealing experimental study at 700, 800, and 900 °C, until the equilibrium in the intracrystalline Fe2+-Mg exchange is reached, using an augite crystal from Miller Range nakhlite (MIL 03346,13) with a composition of about En36Fs24Wo40. These data allowed us to calculate the following new geothermometer calibration for Martian nakhlites:

where The application of this new equation to other Martian nakhlites (NWA 988 and Nakhla) suggests that for augite with composition close to that of MIL 03346, the Tc is up to 170 °C higher with respect to the one calculated using the previous available geothermometer equation, thus suggesting a significantly faster cooling in agreement with petrologic evidence.

Reference
Alvaro M, Domeneghetti MC, Fioretti AM, Cámara F and Marinangeli L (2015) A new calibration to determine the closure temperatures of Fe-Mg ordering in augite from nakhlites. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12436]

Published by arrangement with John Wiley & Sons

Agata Krzesińska¹, Jérôme Gattacceca², Jon M. Friedrich^3,4 and Pierre Rochette²

¹Institute of Geological Sciences, Polish Academy of Sciences INGPAN, Wrocław, Poland
²CEREGE UM34, CNRS, Aix-Marseille University, Aix-en-Provence, France
³Department of Chemistry, Fordham University, Bronx, New York, USA
⁴Department of Earth and Planetary Science, American Museum of Natural History, New York, USA

Petrofabrics in chondrites have the potential to yield important information on the impact evolution of chondritic parent asteroids, but studies involving chondritic petrofabrics are scarce. We undertook an analysis of the Pułtusk H chondrite regolith breccia. Measurements of anisotropy of magnetic susceptibility and quantitative tomographic examination of metal grains are presented here and the results are compared with petrographic observations. The major fabric elements are in Pułtusk shear fractures cutting the light-colored chondritic clasts as well as brittly and semibrittly deformed, cataclased fragments in dark matrix of regolith breccia. Cataclasis is accompanied by rotation of silicate grains and frictional melting. Fabric of metal grains in chondrite is well defined and coherently oriented over the breccia, both in the clasts and in the cataclastic matrix. Metal grains have prolate shapes and they are arranged into foliation plane and lineation direction, both of which are spatially related and kinematically compatible to shear-dominated deformational features. We argue that the fabric of Pułtusk was formed in response to impact-related noncoaxial shear strain. Deformation promoted brittle cataclastic processes and shearing of silicates, and, simultaneously, allowed for ductile metal to develop foliation and lineation. We suggest that plastic flow is the most probable mechanism for the deformation of metal grains in the shear-dominated strain field. The process led also to the formation of large metal nodules and bands in the dark matrix of breccia.

Reference
Krzesińska A, Gattacceca J, Friedrich JM and Rochette P (2015) Impact-related noncoaxial deformation in the Pułtusk H chondrite inferred from petrofabric analysis. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12429]

Published by arrangement with John Wiley & Sons

Paul A. Giesting^1,†, Susanne P. Schwenzer², Justin Filiberto¹, Natalie A. Starkey², Ian A. Franchi², Allan H. Treiman³, Andy G. Tindle⁴ and Monica M. Grady²

¹Department of Geology, Southern Illinois University Carbondale, Carbondale, Illinois, USA
²Department of Physical Science, Planetary and Space Sciences, The Open University, Milton Keynes, UK
³Lunar and Planetary Science Institute, Houston, Texas, USA
⁴Department of Earth Sciences, The Open University, Milton Keynes, UK
^†Department of Geography and Geology, Illinois State University, Illinois, USA

Amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma, but also shock and postshock processes. We have analyzed amphibole and other phases from NWA 2737 melt inclusions, and we evaluate these data along with published values to constrain the crystallization Cl and H2O content of phases in chassignite melt inclusions and the effects of shock on these amphibole grains. Using a model for the Cl/OH exchange between amphibole and melt, we estimate primary crystallization OH contents of chassignite amphiboles. SIMS analysis shows that amphibole from NWA 2737 currently has 0.15 wt% H2O. It has lost ~0.6 wt% H2O from an initial 0.7–0.8 wt% H2O due to intense shock. Chassigny amphibole had on average 0.3–0.4 wt% H2O and suffered little net loss of H2O due to shock. NWA 2737 amphibole has δD ≈ +3700‰; it absorbed Martian atmosphere-derived heavy H in the aftermath of shock. Chassigny amphibole, with δD ≤ +1900‰, incorporated less heavy H. Low H2O/Cl ratios are inferred for the primitive chassignite magma, which had significant effects on melting and crystallization. Volatiles released by the degassing of Martian magma were more Cl-rich than on Earth, resulting in the high Cl content of Martian surface materials.

Reference
Giesting PA, Schwenzer SP, Filiberto J, Starkey NA, Franchi IA, Treiman AH, Tindle AG and Grady MM (2015) Igneous and shock processes affecting chassignite amphibole evaluated using chlorine/water partitioning and hydrogen isotopes. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12430]

Published by arrangement with John Wiley & Sons

Gulchekhra I. Kokhirova* andPulat B. Babadzhanov

Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan, Dushanbe, Republic of Tajikistan

Three bright fireballs belonging to the August θ-Aquillid (ATA) meteor shower were photographed by the Tajikistan fireball network in 2009. Two of them are classified as the meteorite-dropping fireballs according to the determined parameters of the atmospheric trajectories, velocities, masses, and densities. Detection of the more dense bodies among cometary meteoroids points to a heterogeneous composition of the parent comet, and supports the suggestion that some meteorites might originate in the outer solar system, in the given case from the Jupiter-family comet reservoir. A search for the stream’s parent was undertaken among the near-Earth asteroids (NEAs); as a result, the asteroid 2004MB6 was identified as a possible progenitor of the ATA meteoroid stream. Investigation of the orbital evolution of the 2004MB6 and the fireball-producing meteoroid TN170809A showed that both objects have similar secular variations in the orbital elements during 7 kyr. The comet-like orbit of the 2004MB6 and its association with the ATA shower suppose a cometary origin of the asteroid.

Reference
Kokhirova GI and Babadzhanov PB (2015) The August θ-Aquillid fireballs and possible relationship with the asteroid 2004MB6. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12431]

Published by arrangement with John Wiley & Sons

Patrick N. Peplowski¹, David Bazell¹, Larry G. Evans², John O. Goldsten¹, David J. Lawrence¹ and Larry R. Nittler³

¹The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
²Computer Sciences Corporation, Lanham-Seabrook, Maryland, USA
³Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, District of Columbia, USA

A reanalysis of NEAR X-ray/gamma-ray spectrometer (XGRS) data provides robust evidence that the elemental composition of the near-Earth asteroid 433 Eros is consistent with the L and LL ordinary chondrites. These results facilitated the use of the gamma-ray measurements to produce the first in situ measurement of hydrogen concentrations on an asteroid. The measured value, inline image ppm, is consistent with hydrogen concentrations measured in L and LL chondrite meteorite falls. Gamma-ray derived abundances of hydrogen and potassium show no evidence for depletion of volatiles relative to ordinary chondrites, suggesting that the sulfur depletion observed in X-ray data is a surficial effect, consistent with a space-weathering origin. The newfound agreement between the X-ray, gamma-ray, and spectral data suggests that the NEAR landing site, a ponded regolith deposit, has an elemental composition that is indistinguishable from the mean surface. This observation argues against a pond formation process that segregates metals from silicates, and instead suggests that the differences observed in reflectance spectra between the ponds and bulk Eros are due to grain size differences resulting from granular sorting of ponded material.

Reference
Peplowski PN, Bazell D, Evans LG, Goldsten JO, Lawrence DJ and Nittler LR (2015) Hydrogen and major element concentrations on 433 Eros: Evidence for an L- or LL-chondrite-like surface composition. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12434]

Published by arrangement with John Wiley & Sons

Aaron S. Burton^1,†, Hannah McLain³, Daniel P. Glavin¹, Jamie E. Elsila¹, Jemma Davidson⁴, Kelly E. Miller⁵, Alexander V. Andronikov⁵, Dante Lauretta⁵ and Jason P. Dworkin¹

¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
³Catholic University of America, Washington, District of Columbia, USA
⁴Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, District of Columbia, USA
⁵Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
^†Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, Texas, USA

Exogenous delivery of amino acids and other organic molecules to planetary surfaces may have played an important role in the origins of life on Earth and other solar system bodies. Previous studies have revealed the presence of indigenous amino acids in a wide range of carbon-rich meteorites, with the abundances and structural distributions differing significantly depending on parent body mineralogy and alteration conditions. Here we report on the amino acid abundances of seven type 3–6 CK chondrites and two Rumuruti (R) chondrites. Amino acid measurements were made on hot water extracts from these meteorites by ultrahigh-performance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry. Of the nine meteorites analyzed, four were depleted in amino acids, and one had experienced significant amino acid contamination by terrestrial biology. The remaining four, comprised of two R and two CK chondrites, contained low levels of amino acids that were predominantly the straight chain, amino-terminal (n-ω-amino) acids β-alanine, and γ-amino-n-butyric acid. This amino acid distribution is similar to what we reported previously for thermally altered ureilites and CV and CO chondrites, and these n-ω-amino acids appear to be indigenous to the meteorites and not the result of terrestrial contamination. The amino acids may have been formed by Fischer–Tropsch-type reactions, although this hypothesis needs further testing.

Reference
Burton AS, McLain H, Glavin DP, Elsila JE, Davidson J, Miller KE, Andronikov AV, Lauretta D and Dworkin JP
(2015) Amino acid analyses of R and CK chondrites. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12433]

Published by arrangement with John Wiley & Sons

William K. Hartmann

Planetary Science Institute, Tucson, Arizona, USA

The well-recorded Chelyabinsk event, the Tunguska event, and the re-entry of the Zond IV vehicle offer opportunities to compare reactions of modern eyewitnesses to eyewitness accounts of possible ancient fireball events. The first-century book, Acts of the Apostles, gives three separate descriptions of a bright light “from heaven,” which occurred probably in the 30s (C.E.) near Damascus, Syria. The details offer a strikingly good match to a Chelyabinsk-class or Tunguska-class fireball. Among the most impressive, unexpected consistencies with modern knowledge is the first-century description of symptoms of temporary blindness caused by exposure to intense radiation, matching a condition now known as photokeratitis. An analysis of the re-entry of debris from the Russian Zond IV over the eastern United States in 1968 shows how actual perceived phenomena in an unfamiliar natural celestial apparition are often conceived by the observer in terms of current cultural conceptions, and it is suggested that this happened also in the first-century case.

Reference
Hartmann WK (2015) Chelyabinsk, Zond IV, and a possible first-century fireball of historical importance. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12428]

Published by arrangement with John Wiley & Sons