^1,2Jon M. Friedrich, ³Daniel P. Glavin, ⁴Mark L. Rivers, ³P. Dworkin
¹Department of Chemistry, Fordham University, Bronx, New York, USA
²Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
³Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
⁴Center for Advanced Radiation Sources, University of Chicago, Argonne, Illinois, USA

X-ray microcomputed tomography and synchrotron X-ray microcomputed tomography (μCT) are becoming popular tools for the reconnaissance imaging of chondrites. However, there are occasional concerns that the use of μCT may be detrimental to organic components of a chondrite. Soluble organic compounds represent ~2–10% of the total solvent extractable carbon in CI and CM carbonaceous chondrites and amino acids are among the most abundant compounds in the soluble organic fraction. We irradiated two samples of the Murchison CM2 carbonaceous chondrite under conditions slightly harsher (increased beam exposure time) than those typically used for x-ray μCT imaging experiments to determine if detectable changes in the amino acid abundance and distribution relative to a nonexposed control sample occurred. After subjecting two meteorite portions to ionizing radiation dosages of 1.1 kiloGray (kGy) and 1.2 kGy with 48.6 and 46.6 keV monochromatic X-rays, respectively, we analyzed the amino acid content of each sample. Within analytical errors, we found no differences in the amino acid abundances or enantiomeric ratios when comparing the control samples (nonexposed Murchison) and the irradiated samples. We show with calculations that any sample heating due to x-ray exposure is negligible. We conclude that a monochromatic synchrotron X-ray μCT experiment at beamline 13-BM-D of the Advanced Photon Source, which imparts ~1 kGy doses, has no detectable effect on the amino acid content of a carbonaceous chondrite. These results are important for the initial reconnaissance of returned samples from the OSIRIS-REx and Hayabusa 2 asteroid sample return missions.

Reference
Friedrich JM,Glavin DP,Rivers ML, Dworkin JP (2016) Effect of a synchrotron X-ray microtomography imaging experiment on the amino acid content of a CM chondrite. Meteoritics & Planetary Sciences (in Press)
Link to Article [DOI: 10.1111/maps.12595]

Published by arrangement with John Wiley & Sons

¹Peter R. Gordon, ¹Mark A. Sephton
¹Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, SW7 2AZ, UK

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

Reference
Gordon PR, Sephton MA (2016) Rapid habitability assessment of Mars samples by pyrolysis-FTIR. Planetary and Space Sciences (in Press)
Link to Article [doi:10.1016/j.pss.2015.11.019]

¹K.H. McDermott, ¹M.C. Price, ¹M. Cole, ¹M.J. Burchell,
¹Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, Kent, CT2 7NH

During hypervelocity impact (> a few km s-1) the resulting cratering and/or disruption of the target body often outweighs interest on the outcome of the projectile material, with the majority of projectiles assumed to be vaporised. However, on Earth, fragments, often metallic, have been recovered from impact sites, meaning that metallic projectile fragments may survive a hypervelocity impact and still exist within the wall, floor and/or ejecta of the impact crater post-impact. The discovery of the remnant impactor composition within the craters of asteroids, planets and comets could provide further information regarding the impact history of a body. Accordingly, we study in the laboratory the survivability of 1 and 2 mm diameter copper projectiles fired onto ice at speeds between 1.00 – 7.05 km s-1. The projectile was recovered intact at speeds up to 1.50 km s-1, with no ductile deformation, but some surface pitting was observed. At 2.39 km s-1, the projectile showed increasing ductile deformation and broke into two parts. Above velocities of 2.60 km s-1 increasing numbers of projectile fragments were identified post impact, with the mean size of the fragments decreasing with increasing impact velocity. The decrease in size also corresponds with an increase in the number of projectile fragments recovered, as with increasing shock pressure the projectile material is more intensely disrupted, producing smaller and more numerous fragments. The damage to the projectile is divided into four classes with increasing speed and shock pressure: (1) minimal damage, (2) ductile deformation, start of break up, (3) increasing fragmentation, and (4) complete fragmentation. The implications of such behaviour is considered for specific examples of impacts of metallic impactors onto Solar System bodies, including LCROSS impacting the Moon, iron meteorites onto Mars and NASA’s “Deep Impact” mission where a spacecraft impacted a comet.

Reference
McDermott KH, Price MC, Cole M, Burchell MJ (2016) Survivability of copper projectiles during hypervelocity impacts in porous ice: A laboratory investigation of the survivability of projectiles impacting comets or other bodies. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.12.037]
Copyright Elsevier

¹Déborah Chavrit, ¹Manuel A. Moreira, ^1,2Frédéric Moynier
¹Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ Paris Diderot, CNRS, F-75005 Paris, France
²Institut Universitaire de France, Paris, France

Sediments contain interplanetary dust particles (IDPs) carrying extraterrestrial noble gases, such as 3He, which have previously been used to estimate the IDP accretion flux over time and the duration of past environmental events. However, due to its high diffusivity, He can be lost by diffusion either due to frictional heating during entry in the atmosphere, or once it has been incorporated in the sediments. Therefore the absolute values of 3He IDP fluxes cannot be known. Due to its lower diffusivity, Ne is less likely to be lost by diffusion than He and can potentially provide an absolute IDP flux value. Here, we studied the Ne and He isotopic composition of 21 sediments of different ages (3 to 38 Myr, 56 Myr and 183 Myr) in order to better constrain the retention of 3He in such deposits. The samples are carbonates from 2 sites of the Integrated Ocean Drilling Program (IODP), which previously showed evidence of detectable extraterrestrial 3He, and from the Sancerre core in the Paris basin. The 3He/4He, 20Ne/22Ne and 21Ne/22Ne ratios of decarbonated residues vary respectively from 0.09×10−60.09×10−6 to 76.5×10−676.5×10−6, 9.54±0.089.54±0.08 to 11.30±0.6011.30±0.60 and from 0.0295±0.00010.0295±0.0001 to 0.0344±0.00030.0344±0.0003. These isotopic compositions can be explained by a mixing between two terrestrial components (atmosphere and radiogenic He and nucleogenic Ne present in the terrigenous fractions) and an extraterrestrial component. The linear relationship between 20Ne/22Ne and 3He/22Ne ratios shows that the extraterrestrial component has a unique composition and is similar to the He and Ne composition of implanted solar wind. This composition is different from the individual stratospheric IDPs for which the Ne and He isotopic compositions have been measured. We suggest that this difference is due to a bias in the sampling of the individual IDPs previously analyzed toward the largest ones that are more likely to lose He during entry in the atmosphere. Our data further constrains the size of the majority of the IDPs to be less than 10 μm10 μm in diameter. In addition, the constant 3He/22Ne ratio of the extraterrestrial component present in the samples, which is similar to the implanted solar wind composition, suggests that no diffusive loss of 3He occurred in the atmosphere or on the seafloor. Thus, neglecting any non-fractionating He and Ne loss by weathering and/or alteration of the host phases on the seafloor, the extraterrestrial 3He and 20Ne fluxes between 3 to 38 Myr ago are respectively View the MathML source0.2±0.1×10−12 cm3cm−2kyr−1 and View the MathML source0.2±0.1×10−11 cm3cm−2kyr−1. During the sharp increases of the late Eocene and late Miocene, the IDP 3He and 20Ne fluxes reach values up to five times higher.

Reference
Chavrit D, Moreira MA, Moynier F (2016) Estimation of the extraterrestrial 3He and 20Ne fluxes on Earth from He and Ne systematics in marine sediments. Earth and Planetary Science Letters 436, 10–18 Link to Article [doi:10.1016/j.epsl.2015.12.030]
Copyright Elsevier

¹Ying Wang, ¹Weibiao Hsu, ²Xianhua Li,²Qiuli Li, ²Yu Liu,²Guoqiang Tang
¹Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
²State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China

Bulk major element composition, petrography, mineralogy, and oxygen isotope compositions of twenty Al-rich chondrules (ARCs) from five CV3 chondrites (Northwest Africa [NWA] 989, NWA 2086, NWA 2140, NWA 2697, NWA 3118) and the Ningqiang carbonaceous chondrite were studied and compared with those of ferromagnesian chondrules and refractory inclusions. Most ARCs are marginally Al-richer than ferromagnesian chondrules with bulk Al2O3 of 10–15 wt%. ARCs are texturally similar to ferromagnesian chondrules, composed primarily of olivine, pyroxene, plagioclase, spinel, Al-rich glass, and metallic phases. Minerals in ARCs have intermediate compositions. Low-Ca pyroxene (Fs0.6–8.8Wo0.7–9.3) has much higher Al2O3 and TiO2 contents (up to 12.5 and 2.3 wt%, respectively) than that in ferromagnesian chondrules. High-Ca pyroxene (Fs0.3–2.0Wo33–54) contains less Al2O3 and TiO2 than that in Ca,Al-rich inclusions (CAIs). Plagioclase (An77–99Ab1–23) is much more sodic than that in CAIs. Spinel is enriched in moderately volatile element Cr (up to 6.7 wt%) compared to that in CAIs. Al-rich enstatite coexists with anorthite and spinel in a glass-free chondrule, implying that the formation of Al-enstatite was not due to kinetic reasons but is likely due to the high Al2O3/CaO ratio (7.4) of the bulk chondrule. Three ARCs contain relict CAIs. Oxygen isotope compositions of ARCs are also intermediate between those of ferromagnesian chondrules and CAIs. They vary from −39.4‰ to 13.9‰ in δ18O and yield a best fit line (slope = 0.88) close to the carbonaceous chondrite anhydrous mineral (CCAM) line. Chondrules with 5–10 wt% bulk Al2O3 have a slightly more narrow range in δ18O (−32.5 to 5.9‰) along the CCAM line. Except for the ARCs with relict phases, however, most ARCs have oxygen isotope compositions (>−20‰ in δ18O) similar to those of typical ferromagnesian chondrules. ARCs are genetically related to both ferromagnesian chondrules and CAIs, but the relationship between ARCs and ferromagnesian chondrules is closer. Most ARCs were formed during flash heating and rapid cooling processes like normal chondrules, only from chemically evolved precursors. ARCs extremely enriched in Al and those with relict phases could have had a hybrid origin (Krot et al. 2002) which incorporated refractory inclusions as part of the precursors in addition to ferromagnesian materials. The occurrence of melilite in ARCs indicates that melilite-rich CAIs might be present in the precursor materials of ARCs. The absence of melilite in most ARCs is possibly due to high-temperature interactions between a chondrule melt and the solar nebula.

Reference
Wang Y, Hsu W, Li X, Li Q, Liu Y, Tang G (2015) Petrology, mineralogy, and oxygen isotope compositions of aluminum-rich chondrules from CV3 chondrites. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12590]
Published by arrangement with John Wiley & Sons

^1,2Honglei Lin, ¹Xia Zhang, ^1,2Tong Shuai, ¹Lifu Zhang,
²Yanli Sun
¹State Key Laboratory of Remote Sensing Sciences, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China
²University of Chinese Academy of Sciences, Beijing 100049, China

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

Reference
Lin H, Zhang X, Shuai T, Zhang L, Sun Y (2016) Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2015.12.007]

^1,2David R. Thompson et al. (>10)*¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.
²Imaging Spectroscopy, Jet Propulsion Laboratory, California Institute of Technology.
*Find the extensive, full author and affiliation list on the publishers website

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

Reference
Thompson DR et al. (2015) Automating X-ray Fluorescence Analysis for Rapid Astrobiology Surveys. Astrobiology 15, 961-976
Link to Article [doi:10.1089/ast.2015.1349]

¹Burbine, T.H.
¹Department of Astronomy, Mount Holyoke College, South Hadley, MA 01075, USA

Considerable progress has been made in the last few years in determining asteroid chemistries and mineralogies. Dedicated spacecraft missions have allowed mineralogical predictions based on ground-based data to be confirmed or refuted. These missions include NEAR-Shoemaker to (253) Mathilde and (433) Eros, Hayabusa to (25143) Itokawa, and Dawn to (4) Vesta and (1) Ceres, the upcoming Hayabusa2 to (162173) Ryugu, and the upcoming OSIRIS-Rex to (101955) Bennu. All of these missions have or will make significant advances that could not have been made through just Earth-based observations. The recovery of Almahata Sitta from 2008 TC3 was a rare opportunity to recover meteorite samples from a spectrally observed body from a naturally occurring event. This review will discuss the importance of spacecraft missions to asteroids.

Reference
Burbine TH (2015) Advances in determining asteroid chemistries and mineralogies. Chemie der Erde (in Press)
Link to Article [doi:10.1016/j.chemer.2015.09.003]
Copyright Elsevier

¹Anthony J. Carrasquillo, ²Changqun Cao, ³Douglas H. Erwin, ¹Roger E. Summons
¹Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
²State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology & Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
³Department of Paleobiology, National Museum of Natural History, PO BOX 37012, Washington, Washington DC 20013-7012, USA

Fullerene (C60) have been reported in a number of geologic samples and, in some cases, attributed to carbonaceous materials delivered during bolide impact events. The extraction and detection of C60 poses significant analytical challenges, and some studies have been called into question due to the possibility of C60 forming in situ. Here, we extracted samples taken from the Permian-Triassic Boundary section in Meishan, South China and the Cretaceous-Paleogene Boundary exposed at Stevns Klint, Denmark, and analyzed the residues using a fast and reliable method for quantifying C60. Extraction of both whole rock and completely demineralized samples were completed under conditions that previously yielded C60 as well as using an optimized approach based on recent literature reports. These extracts were analyzed using mass spectrometry with the soft-ionization techniques, Atmospheric Pressure Chemical Ionization (APCI) and Electrospray Ionization (ESI), which have not been shown to form fullerenes in-situ. In no case were we able to detect C60, nor could we corroborate previous reports of its occurrence in these sediments, thereby challenging the utility of fullerene as a proxy for bolide impacts or mass extinction events.

Reference
Carrasquillo AJ,Cao C,Erwin DH,Summons RE (2015) Non-detection of C60 fullerene at two mass extinction horizons. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.12.017]
Copyright Elsevier

¹J.D. Gilmour, ¹G. Holland, ²A.B. Verchovsky, ³A.V. Fisenko, ¹S.A. Crowther, ¹G. Turner
¹School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, United Kingdom
²Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
³Vernadsky Inst Geochem & Analyt Chem RAS, 19 Kosygin St, Moscow 119991, Russia

We identify new xenon components in a nanodiamond-rich residue from the reduced CV3 chondrite Efremovka. We demonstrate for the first time that these, and the previously identified xenon components Xe-P3 and Xe-P6, are associated with elevated I/Xe ratios. The 129I/127I ratio associated with xenon loss from these presolar compositions during processing on planetesimals in the early solar system was (0.369 ± 0.019) x 10-4, a factor of 3-4 lower than the canonical value. This suggests either incorporation of iodine into carbonaceous grains before the last input of freshly synthesized 129I to the solar system’s precursor material, or loss of noble gases during processing of planetesimals around 30 Myr after solar system formation. The xenon/iodine ratios and model closure ages were revealed by laser step pyrolysis analysis of a neutron-irradiated, coarse-grained nanodiamond separate.

Three distinct low temperature compositions are identified by characteristic I/Xe ratios and 132Xe/136Xe ratios. There is some evidence of multiple compositions with distinct I/Xe ratios in the higher temperature releases associated with Xe-P6. The presence of iodine alongside Q-Xe and these components in nanodiamonds constrains the pathway by which extreme volatiles entered the solid phase and may facilitate the identification of their carriers.

There is no detectable iodine contribution to the presolar Xe-HL component, which is released at intermediate temperatures; this, suggests a distinct trapping process. Releases associated with the other components all include significant contributions of 128Xe produced from iodine by neutron capture during reactor irradiation.

We propose a revised model relating the origin of Xe-P3 (which exhibits an s-process deficit) through a “Q-process” to the Q component (which makes the dominant contribution to the heavy noble gas budget of primitive material). The Q-process incorporates noble gases and iodine into specific carbonaceous phases with mass dependent fractionation relative to the ambient composition. Q-Xe is dominated by the products of this “Q-process” occurring shortly before or during solar system formation. Carriers that trapped xenon by earlier Q-process events were altered, perhaps by supernova shocks, converting some Q carriers into P3 carriers. Unlike Q carriers, these carriers preserve the isotopic signature of the xenon they trapped through oxidation of samples in the laboratory. P3 carriers thus disproportionately sample xenon that was incorporated before galactic chemical evolution had produced the solar xenon signature by enriching ambient xenon with s-process material.

Reference
Gilmour JD, Holland G, Verchovsky AB, Fisenko AV, Crowther SA, Turner G (2016) Xenon and iodine reveal multiple distinct exotic xenon components in Efremovka “nanodiamonds”. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.12.028]
Copyright Elsevier