¹J. M. Young,¹T. D. Glotch,²M. Yesiltas,³V. E. Hamilton,⁴L. B. Breitenfeld,⁵H. A. Bechtel,⁵S. N. Gilbert Corder,⁵Z. Yao
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007166]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
²Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, Turkey
³Southwest Research Institute, Boulder, CO, USA
⁴Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
⁵Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
Published by arrangement with John Wiley & Sons

Mid-infrared (MIR) spectroscopy has been used with great success to quantitatively determine the mineralogy of geologic samples. It has been employed in a variety of contexts from determining bulk composition of powdered samples to spectroscopic imaging of rock thin sections via micro-FTIR. Recent advances allow for IR measurements at the nanoscale. Near field nanoscale infrared imaging and spectroscopy with a broadband source (nano-FTIR) enable understanding of the spatial relationships between compositionally distinct materials within a sample. This will be of particular use when analyzing returned samples from Bennu and Ryugu, which are thought to be compositionally like CI or CM2 carbonaceous chondrites. Returned samples will likely contain olivine/pyroxene chondrules that have been transformed into hydrous phyllosilicates, sulfides, carbonates, and other alteration phases. The use of near-field infrared techniques to probe the boundaries between once pristine chondrules and alteration phases at the nanoscale is a novel approach to furthering our understanding of the compositional evolution of carbonaceous asteroids and the processes that drive their evolution. Here we report the results of nano-FTIR spectroscopy and imaging measurements performed on the carbonaceous chondrite Allan Hills (ALH) 83100 (CM1/2). We show with nanoscale resolution that spatially resolved Fe-Mg variations exist within the phylosilicates around a chondrule rim. We also present effects of crystal orientation on the nano-FTIR spectra to account for the spectral differences between the meteorite and mineral spectra.

¹S. Griffin,^1,2,3,4L. Daly,⁵S. Piazolo,²L. V. Forman,⁶B. E. Cohen,¹M. R. Lee,⁷P. W. Trimby,^8,9R. J. Baumgartner,^2,10,11G. K. Benedix,¹B. Hoefnagels
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007082]
¹School of Geographical and Earth Sciences, University of Glasgow, UK
²School of Earth and Planetary Sciences, Space Science and Technology Centre, Curtin University, Australia
³Australian Centre for Microscopy and Microanalysis, The University of Sydney, Australia
⁴Department of Materials, University of Oxford, UK
⁵School of Earth and Environment, University of Leeds, UK
⁶Department of Materials, University of Oxford, UK. 5School of Geosciences, University of Edinburgh, UK
⁷Oxford Instruments Nano analysis, High Wycombe, UK
⁸School of Biological, Earth and Environmental Sciences, The University of New South Wales, Kensington, NSW, Australia
⁹CSIRO Mineral Resources, Australian Resources Research Centre, Kensington, WA, Australia
¹⁰Department of Earth and Planetary Sciences, Western Australia Museum, Australia
¹¹Planetary Institute, USA
Published by arrangment with John Wiley & Sons

Deformation is a near ubiquitous process that is observed within nearly all naturally forming rocks. Electron backscatter diffraction (EBSD) is a technique that enables slip-systems (a form of plastic deformation) to be inferred from intra-crystalline misorientations at a comparable scale to representative CPO analysis (≥300 crystals for the nakhlites). Extensive laboratory and studies on naturally occurring samples have identified preferential mantle condition extrinsic parameters for specific slip-system signatures within olivine and clinopyroxene. Intra-crystalline misorientation patterns for olivine and augite (high Ca-clinopyroxene) for 16 different Martian nakhlite meteorites (21 sections) were analysed and assessed against these known parameters. Investigation of high and low deformation regions within the nakhlites revealed a shift in intra-crystalline misorientation patterns for 10 of the 21 sections. Interpreted as both shock (high deformations) and emplacement (low deformation) signatures. The observed variations in deformation patterns for the two main regimes of deformation indicate heterogeneous sampling of the nakhlite ejecta crater. Our findings indicate that shock deformation is prevalent throughout the nakhlites, and that great care needs to be taken when interpreting intra-crystalline misorientations of crystals within apparent lower deformation regions.