^1,2M.D. Suttle et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13938]
¹School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
²Planetary Materials Group, Natural History Museum, Cromwell Road, London, SW7 5BD UK
Published by arrangement with John Wiley & Sons

The Winchcombe meteorite is a CM chondrite breccia composed of eight distinct lithological units plus a cataclastic matrix. The degree of aqueous alteration varies between intensely altered CM2.0 and moderately altered CM2.6. Although no lithology dominates, three heavily altered rock types (CM2.1–2.3) represent >70 area%. Tochilinite–cronstedtite intergrowths (TCIs) are common in several lithologies. Their compositions can vary significantly, even within a single lithology, which can prevent a clear assessment of alteration extent if only TCI composition is considered. We suggest that this is due to early alteration under localized geochemical microenvironments creating a diversity of compositions and because later reprocessing was incomplete, leaving a record of the parent body’s fluid history. In Winchcombe, the fragments of primary accretionary rock are held within a cataclastic matrix (~15 area%). This material is impact-derived fallback debris. Its grain size and texture suggest that the disruption of the original parent asteroid responded by intergranular fracture at grain sizes <100 μm, while larger phases, such as whole chondrules, splintered apart. Re-accretion formed a poorly lithified body. During atmospheric entry, the Winchcombe meteoroid broke apart with new fractures preferentially cutting through the weaker cataclastic matrix and separating the breccia into its component clasts. The strength of the cataclastic matrix imparts a control on the survival of CM chondrite meteoroids. Winchcombe’s unweathered state and diversity of lithologies make it an ideal sample for exploring the geological history of the CM chondrite group.

^1,2Ildiko Gyollai,^2,3Ákos Kereszturi,^4,5Elias Chatzitheodoridis,⁶Zsolt Kereszty,^1,2Máté Szabó,^2,7Csilla Király,^2,7Zoltan Szalai
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13931]
¹Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Budaorsi ut 45, H-1112 Budapest, Hungary
²CSFK, MTA Centre of Excellence, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary
³Konkoly Thege Miklos Astronomical Institute, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary
⁴Department of Geological Sciences, School of Mining and Metallurgical Engineering, National Technical University of Athens 9, Heroon Polytechneiou str., GR-15780 Zografou, Athens, Greece
⁵Network of Researchers on the Chemical Evolution of Life (NoRCEL), LS2 9JT Leeds, UK
⁶Private Collector at IMCA (IMCA#6251) and Meteoritical Society, H-9010 Győr, Hungary
⁷Geographical Research Institute, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Budaorsi ut 45, H-1112 Budapest, Hungary
Published by arrangement with John Wiley & Sons
The analysis of the Csatalja H4 chondrite (which was found in August 2012) suggests shock-related textures and spatial inhomogeneities, indicating a complex geological history. In the most heavily fractured and sheared units, small opaque grains and older fractures have locally enhanced the shock effect, producing melt. While the impact textures were evident in most units of the meteorite, mechanical shearing is apparent in only two units, suggesting that these units might have been present at somewhat different locations inside the parent body. Shearing also occurred at the border of the so-called xenolith unit, confirming its mechanical mixing with the other units. Besides fragmentation and melting, chemical changes due to impact have also been identified, producing compositional homogenization of olivines in 30% of the investigated area of the sample’s thin section (23 mm2), and moderate accumulation of Fe, Ca, and Na in the strongly shocked zones, initiating crystallization of feldspar in veins with a specific spatial distribution (feldspar glass with metal–sulfide globules). Analyzing the high P–T minerals, the peak shock pressure and temperature values differed substantially in the various units, ranging between 2 and 17 GPa, 100 and >1200 °C. The xenolith unit crystallized more slowly after the impact event and does not show shock impact alterations, suggesting that it was formed in a deeper region of the parent body. This was later shifted to its current surroundings and was lithified (fixed) to the rest of the sample. This “randomly selected” Csatalja sample provides information on the range of the formation temperatures, pressures, and processes that contributed to the heterogeneity of meteorites at the mm spatial scale, in general. The identified heterogeneity is a result not purely of the shock effects but also of the different pre-shock structural characteristics. The shock also mixed fragments mechanically that have been formed at different environments, with at least several dozens or even 100 m depth in the parent body.

¹Ryan Scott Jakubek,¹Marc D. Fries
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13940]
¹Jacobs, NASA Johnson Space Center, Mail Code XI2, Houston, Texas, 77058 USA
²NASA Johnson Space Center, Houston, Texas, 77058 USA
Published ba arrangement with John Wiley & Sons

The study of astromaterials generally involves the distribution of limited sample to many laboratories for analysis. Maximum scientific yield for a sample occurs when the data and results from different studies are examined as a collective. This collective examination of results will be particularly important for upcoming sample return missions including Mars sample return and OSIRIS-REx. When comparing results across laboratories, instrument calibration is of key importance. For Raman data, this includes the calibration of all three Raman band parameters: peak wavenumber position, bandwidth, and intensity. Although wavenumber is routinely calibrated, bandwidth and intensity are not; though they are commonly compared across studies. In addition, Raman instrument calibration is time dependent. An understanding of the time dependence of instrument calibration is important for proper calibration. Here, we use a mixture of well-established and recently developed calibration techniques to propose a standard method of calibrating Raman astromaterial data across laboratories to maximize the scientific value of the data.