J. W. Aerts¹, A. Elsaesser², W. F. M. Röling¹ and P. Ehrenfreund^2,3
1Molecular Cell Physiology, Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam, the Netherlands
²Leiden Observatory, Leiden University, Leiden, the Netherlands
³Space Policy Institute, George Washington University, Washington, District of Columbia, USA

The Orgueil meteorite has become one of the most well-studied carbonaceous meteorites, after it fell in France 150 yr ago. Extraterrestrial organic compounds such as amino acids and nucleobases in the parts per billion ranges were identified in Orgueil samples with supporting isotopic analyses. However, speculations of terrestrial contamination such as organic inclusions in the form of microbes and seeds accompanied the analyses of the Orgueil meteorite ever since its fall. By using molecular analysis, we performed DNA extractions and spiking experiments combined with 16S and 18S rRNA gene targeted PCR amplification to quantify the level of terrestrial biocontamination. Our results indicate that terrestrial contamination with DNA was insignificant in the investigated meteorite fraction. We also remeasured and confirmed concentrations of amino acids found in previous studies and conclude that their rather high concentrations and distribution cannot be explained by terrestrial contamination with microorganisms alone. These results represent the first analysis using DNA-directed tools in the analysis of the Orgueil meteorite to determine trace levels of biomarkers.

Reference
Aerts JW, Elsaesser A, Röling WFM and Ehrenfreund P (2016) A contamination assessment of the CI carbonaceous meteorite Orgueil using a DNA-directed approach. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12629]
Published by arrangement with John Wiley & Sons

Diana Bolser¹, Thomas J. Zega^2,3, Abu Asaduzzaman³, Stefan Bringuier³, Steven B. Simon⁴, Lawrence Grossman⁴, Michelle S. Thompson² and Kenneth J. Domanik^1
1Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, USA
²Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, Tucson, Arizona, USA
³Department of Materials Science & Engineering, University of Arizona, Tucson, Arizona, USA
⁴Department of Geophysical Sciences, University of Chicago, Chicago, Illinois, USA

A coordinated, electron-backscatter-diffraction (EBSD) and transmission electron microscope (TEM) study was undertaken to obtain information on the origin of rims on refractory inclusions in the Allende and Axtell CV3 chondrites. These measurements were supported by theoretical modeling using density functional theory. Crystal-orientation analysis of Wark-Lovering rims via EBSD revealed pyroxene grains with similar crystallographic orientations to one another in both inclusions. An epitaxial relationship between grains within the diopside and anorthite rim layers was observed in Allende. TEM examination of the rims of both samples also revealed oriented crystals at depth. The microstructural data on the rims suggest that grain clusters grew in the form of three-dimensional islands. Density functional theory calculations confirm that formation of oriented grain islands is the result of energy minimization at high temperature. The results point toward condensation as the mode of origin for the rims studied here.

Reference
Bolser D, Zega TJ, Asaduzzaman A, Bringer S, Simon SB, Grossman L, Thompson MS and Domanik KJ (2016) Microstructural analysis of Wark-Lovering rims in the Allende and Axtell CV3 chondrites: Implications for high-temperature nebular processes. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12620]
Published by arrangement with John Wiley & Sons

Motoo Ito¹ and Scott Messenger^2
1Robert M Walker Laboratory for Space Science, EISD/ARES, NASA Johnson Space Center, Houston, Texas, USA
²JAMSTEC, Kochi Institute for Core Sample Research, Nankoku, Kochi, Japan

We have established analytical procedures for quantitative rare earth element (REE) measurements by NanoSIMS 50L ion microprobe with 2–10 μm spatial resolution. Measurements are performed by multidetection using energy filtering under several static magnetic field settings. Relative sensitivity factors and REE oxide/REE element secondary ion ratios that we determined for the NanoSIMS match values previously determined for other ion microprobes. REE measurements of 100 ppm REE glass standards yielded reproducibility and accuracy of 0.5–2.5% and 5–15%, respectively. REE measurements of minerals of an Allende type-A CAI, 7R19-1, were performed using three different methods: spot analysis, line profile, and imaging. These data are in excellent agreement with previous REE measurements of this inclusion by IMS-3f ion microprobe. The higher spatial resolution NanoSIMS measurements provide additional insight into the formation process of this CAI and offer a promising new tool for analysis of fine-grained and complexly zoned materials.

Reference
Ito M and Messenger S (2016) Rare earth element measurements and mapping of minerals in the Allende CAI, 7R19-1, by NanoSIMS ion microprobe. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12623]
Published by arrangement with John Wiley & Sons

¹Scott Harlan et al. (>10)*
¹Planetary Geology Lab, Institute of Geological Sciences, Polish Academy of Sciences, Wrocław, Poland
*Find the extensive, full author and affiliation list on the publishers website

Meteorites have been found on the small Misfits Flat dry lakebed near Stagecoach, Nevada (119.382W, +39.348N). Since the first find on Sept. 22, 2013, a total of 58 stones of weathering stage W2/3 with a combined mass of 339 g have been collected in 19 visits to the area. This small (3.3 × 3.6 km) lakebed is now a newly designated dense collection area (DCA). Most meteorites were found in a small 350 × 180 m area along the north shore and most are fragments of several broken individual stones. Three of these fragments were classified as an LL4/5 of shock stage S2, now named Misfits Flat 001, one of which (stone MF33) fell 8.1 ± 1.3 ka ago based on the 14C terrestrial age, assuming it came from a 20–80 cm diameter meteoroid. In addition, a small darkly crusted meteorite MF34, now named Misfits Flat 002, was found 820 m WSW from the main mass. This meteorite is classified as an LL5 ordinary chondrite with shock stage S4/5. The meteorite is saturated in 14C at 63 dpm kg−1, suggesting it originated from the center of a 0.5 m diameter meteoroid, or deep inside a ~1.0 m meteoroid, less than 300 yr ago. Accounts exist of a fireball seen at 13:15 UT on March 2, 1895, that are consistent with the find location of Misfits Flat 002.

Reference
Harlan S et al. (2016) Meteorites found on Misfits Flat dry lake, Nevada. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12619]
Published by arrangement with John Wiley & Sons

Derek W. G. Sears¹, Hazel Sears¹, Denton S. Ebel², Sean Wallace² andJon M. Friedrich^2,3
1NASA Ames Research Center/BAER Institute, Mountain View, California, USA
²American Museum of Natural History, New York, New York, USA
³Department of Chemistry, Fordham University, New York, New York, USA

X-ray computed tomography has become a popular means for examining the interiors of meteorites and has been advocated for routine curation and for the examination of samples returned by missions. Here, we report the results of a blind test that indicate that CT imaging deposits a considerable radiation dose in a meteorite and seriously compromises its natural radiation record. Ten vials of the Bruderheim L6 chondrite were placed in CT imager and exposed to radiation levels typical for meteorite studies. Half were retained as controls. Their thermoluminescence (TL) properties were then measured in a blind test. Five of the samples had TL data unaltered from their original (~10 cps) while five had very strong signals (~20,000 cps). It was therefore very clear which samples had been in the CT scanner. For comparison, the natural TL signal from Antarctic meteorites is ~5000–50,000 cps. Using the methods developed for Antarctic meteorites, the apparent dose absorbed by the five test samples was calculated to be 83 ± 5 krad, comparable with the highest doses observed in Antarctic meteorites and freshly fallen meteorites. While these results do not preclude the use of CT scanners when scientifically justified, it should be remembered that the record of radiation exposure to ionizing radiations for the sample will be destroyed and that TL, or the related optically stimulated luminescence, are the primary modern techniques for radiation dosimetry. This is particularly important with irreplaceable samples, such as meteorite main masses, returned samples, and samples destined for archive.

Reference
Sears DWG, Sears H, Ebel DS, Wallace S andFriedrich JM (2016) X-ray computed tomography imaging: A not-so-nondestructive technique. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12622]
Published by arrangement with John Wiley & Sons

François L. H. Tissot, Nicolas Dauphas, Lawrence Grossman
Origins Lab, Department of the Geophysical Sciences, and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA.

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

Reference
Tissot FLH, Dauphas N, Grossman L (2016) Origin of uranium isotope variations in early solar nebula condensates. Science Advances e1501400
Link to Article [doi:10.1126/sciadv.1501400]

¹A. Losiak et al. (>10)*
¹Planetary Geology Lab, Institute of Geological Sciences, Polish Academy of Sciences, Wrocław, Poland
*Find the extensive, full author and affiliation list on the publishers website

The estimates of the age of the Kaali impact structure (Saaremaa Island, Estonia) provided by different authors vary by as much as 6000 years, ranging from ~6400 to ~400 before current era (BCE). In this study, a new age is obtained based on 14C dating charred plant material within the proximal ejecta blanket, which makes it directly related to the impact structure, and not susceptible to potential reservoir effects. Our results show that the Kaali crater was most probably formed shortly after 1530–1450 BCE (3237 ± 10 14C yr BP). Saaremaa was already inhabited when the bolide hit the Earth, thus, the crater-forming event was probably witnessed by humans. There is, however, no evidence that this event caused significant change in the material culture (e.g., known archeological artifacts) or patterns of human habitation on Saaremaa.

Reference
Losiak A et al. (2016) Dating a small impact crater: An age of Kaali crater (Estonia) based on charcoal emplaced within proximal ejecta. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12616]
Published by arrangement with John Wiley & Sons

¹Ronny Schoenberg, ¹Alexandra Merdian, ²Chris Holmden, ¹Ilka C. Kleinhanns, ¹Kathrin Haßler, ¹Martin Wille, ¹Elmar Reitter
¹Department of Geosciences, University of Tuebingen, Germany
²Department of Geological Sciences, University of Saskatchewan, Canada

The depletion of chromium in Earth’s mantle (∼2,700 ppm) in comparison to chondrites (∼4,400 ppm) indicates significant incorporation of chromium into the core during our planet’s metal-silicate differentiation, assuming that there was no significant escape of the moderately volatile element chromium during the accretionary phase of Earth. Stable Cr isotope compositions – expressed as the ‰-difference in 53Cr/52Cr from the terrestrial reference material SRM979 (δ53/52CrSRM979 values) – of planetary silicate reservoirs might thus yield information about the conditions of planetary metal segregation processes when compared to chondrites. The stable Cr isotopic compositions of 7 carbonaceous chondrites, 11 ordinary chondrites, 5 HED achondrites and 2 martian meteorites determined by a double spike MC-ICP-MS method are within uncertainties indistinguishable from each other and from the previously determined δ53/52CrSRM979 value of –0.124 ± 0.101 ‰ for the igneous silicate Earth. Extensive quality tests support the accuracy of the stable Cr isotope determinations of various meteorites and terrestrial silicates reported here. The uniformity in stable Cr isotope compositions of samples from planetary silicate mantles and undifferentiated meteorites indicates that metal-silicate differentiation of Earth, Mars and the HED parent body did not cause measurable stable Cr isotope fractionation between these two reservoirs. Our results also imply that the accretionary disc, at least in the inner solar system, was homogeneous in its stable Cr isotopic composition and that potential volatility loss of chromium during accretion of the terrestrial planets was not accompanied by measurable stable isotopic fractionation. Small but reproducible variations in δ53/52CrSRM979 values of terrestrial magmatic rocks point to natural stable Cr isotope variations within Earth’s silicate reservoirs. Further and more detailed studies are required to investigate whether silicate differentiation processes, such partial mantle melting and crystal fractionation, can cause stable Cr isotopic fractionation on Earth and other planetary bodies.

Reference
Schoenberg R, Merdian A, Holmden C, Kleinhanns IC, Haßler K, Wille M, Reitter E (2016) The stable Cr isotopic compositions of chondrites and silicate planetary reservoirs. Geochmica et Cosmochmica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2016.03.013]
Copyright Elsevier

^1,2Geoffrey H. Howarth, ^3,4Yang Liu, ^3,4Yang Chen, ¹John F. Pernet-Fisher, ¹Lawrence A. Taylor
¹Earth and Planetary Sciences Department, Planetary Geosciences Institute, University of Tennessee, Knoxville, Tennessee, USA
²Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa
³Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
⁴Division of Geology and Planetary Science, California Institute of Technology, Pasadena, California, USA

Apatite is the major volatile-bearing phase in Martian meteorites, containing structurally bound fluorine, chlorine, and hydroxyl ions. In apatite, F is more compatible than Cl, which in turn is more compatible than OH. During degassing, Cl strongly partitions into the exsolved phase, whereas F remains in the melt. For these reasons, the volatile concentrations within apatite are predictable during magmatic differentiation and degassing. Here, we present compositional data for apatite and merrillite in the paired enriched, olivine-phyric shergottites LAR 12011 and LAR 06319. In addition, we calculate the relative volatile fugacities of the parental melts at the time of apatite formation. The apatites are dominantly OH-rich (calculated by stoichiometry) with variable yet high Cl contents. Although several other studies have found evidence for degassing in the late-stage mineral assemblage of LAR 06319, the apatite evolutionary trends cannot be reconciled with this interpretation. The variable Cl contents and high OH contents measured in apatites are not consistent with fractionation either. Volatile fugacity calculations indicate that water and fluorine activities remain relatively constant, whereas there is a large variation in the chlorine activity. The Martian crust is Cl-rich indicating that changes in Cl contents in the apatites may be related to an external crustal source. We suggest that the high and variable Cl contents and high OH contents of the apatite are the results of postcrystallization interaction with Cl-rich, and possibly water-rich, crustal fluids circulating in the Martian crust.

Reference
Howarth GH, Liu Y, Chen Y, Pernet-Fisher JF, Taylor LA (2016) Postcrystallization metasomatism in shergottites: Evidence from the paired meteorites LAR 06319 and LAR 12011. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12576]
Published by arrangement with John Wiley & Sons

¹N. G. Rudraswami, ¹M. Shyam Prasad, ²E. V. S. S. K. Babu,²T. Vijaya Kumar
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Goa, India
²National Geophysical Research Institute (Council of Scientific and Industrial Research), Hyderabad, India

Micrometeorites that pass through the Earth’s atmosphere undergo changes in their chemical compositions, thereby making it difficult to understand if they are sourced from the matrix, chondrules, or calcium–aluminum-rich inclusions (CAIs). These components have the potential to provide evidence toward the understanding of the early solar nebular evolution. The variations in the major element and trace element compositions of 155 different type (scoriaceous, relict bearing, porphyritic, barred, cryptocrystalline, and glass) of S-type cosmic spherules are investigated with the intent to decipher the parent sources using electron microprobe and laser ablation inductively coupled plasma-mass spectrometry. The S-type cosmic spherules appear to show a systematic depletion in volatile element contents, but have preserved their refractory trace elements. The trends in their chemical compositions suggest that the S-type spherules comprise of components from similar parent bodies, that is, carbonaceous chondrites. Large fosteritic relict grains observed in this investigation appear to be related to the fragments of chondrules from carbonaceous chondrites. Furthermore, four spherules (two of these spherules enclose spinels and one comprised entirely of a Ca-Al-rich plagioclase) show enhanced trace element enrichment patterns that are drastically different from all the other 151 cosmic spherules. The information on the chemical composition and rare earth elements (REEs) on cosmic spherules suggest that the partially to fully melted ones can preserve evidences related to their parent bodies. The Ce, Eu, and Tm anomalies found in the cosmic spherules have similar behavior as that of chondrites. Distinct correlations observed between different REEs and types of cosmic spherules reflect the inherited properties of the precursors.

Reference
Rudraswami NG, Prasad MS, Babu EVSSK, Kumar TV (2016) Major and trace element geochemistry of S-type cosmic spherules. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12618]
Published by arrangement with John Wiley & Sons