¹T. H. Burbine,²P. C. Buchanan,³R. L. Klima,⁴R. P. Binzel
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2018JE005561]
¹Department of Astronomy, Mount Holyoke College, South Hadley, MA, USA
²Department of Geology, Kilgore College, Kilgore, TX, USA
³Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
⁴Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
Published by arrangement with John Wiley & Sons

We compare methods for determining the pyroxene mineralogies of V‐type near‐Earth asteroids from their reflectance spectra. We evaluate whether band centers derived from the spectra of synthetic pyroxenes can be used to achieve greater analytical accuracy than is achieved through the use of band centers derived from the spectra of basaltic achondrites (howardites, eucrites, diogenites or HEDs). We conclude that band centers derived from the reflectance spectra of synthetic pyroxenes with known mineralogies do not provide useful diagnostic information to derive equations for determining accurate pyroxene compositions of V‐type asteroids. Band centers from the reflectance spectra of HEDs with known pyroxene mineralogies can be used to derive equations for determining accurate pyroxene compositions of V‐type asteroids. HEDs are physical mixtures of a number of different types of pyroxenes and best simulate the surfaces of V‐type asteroids. Formulas using the Band I center appear best for determining asteroid pyroxene mineralogies for V‐type asteroids due to the current difficulty in doing accurate temperature corrections to the Band II center. Most of thes observed V‐type near‐Earth asteroids have interpreted mineralogies similar to eucrites or howardites. One of the observed near‐Earth asteroids could possibly have a surface mineralogy similar to diogenites.

¹J. T. Wilson,¹D. J. Lawrence,¹P. N. Peplowski,¹J. T. S. Cahill,²V. R. Eke,²R. J. Massey,³L. F. A. Teodoro
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2018JE005589]
¹The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
²Institute for Computational Cosmology, Department of Physics, Durham University, Science Laboratories, Durham, UK
³BAER, Planetary Systems Branch, Space Sciences and Astrobiology Division, MS 245‐3, NASA Ames Research CenterMoffett Field, CA, USA
Published by arrangement with John Wiley & Sons

We present improved resolution maps of the Lunar Prospector Neutron Spectrometer thermal, epithermal and fast neutron data and Gamma‐Ray Spectrometer Th‐line fluxes via global application of pixon image reconstruction techniques. With the use of mock data sets, we show that the pixon image reconstruction method compares favorably with other methods that have been used in planetary neutron and gamma‐ray spectroscopy. The improved thermal neutron maps are able to clearly distinguish variations in composition across the lunar surface, including within the lunar basins of Hertzsprung and Schrödinger. The improvement in resolution reveals a correlation between albedo and thermal neutron flux within the basins. The consequent increase in dynamic range confirms that Hertzsprung basin contains one of the most anorthositic parts of the lunar crust, including nearly pure anorthite over a region tens of km in diameter. At Orientale, the reconstructed epithermal neutron data show broad overlap with cpr but there remains a mismatch between measures of regolith maturity that sample the surface and those that probe the near‐subsurface, which is consistent with a complex layering scenario.

¹Justin Filiberto et al. (>10)
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2018JE005635]
¹Southern Illinois University, Department of GeologyCarbondale, IL, USA
²School of Environment, Earth and Ecosystem Sciences, Walton Hall, The Open UniversityMilton Keynes, MK, UK
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 6963 was found in Guelmim‐Es‐Semara, Morocco, and based on its bulk chemistry and oxygen isotopes, it was classified as a Martian meteorite. On the basis of a preliminary study of the textures and crystal sizes, it was re‐subclassified as a gabbroic shergottite because of the similarity with terrestrial and lunar gabbros. However, the previous work was not a quantitative investigation of NWA 6963; to supplement the original re‐subclassification and enable full comparison between this and other Martian samples, here we investigate the mineralogy, petrology, geochemistry, quantitative textural analyses, and spectral properties of gabbroic shergottite NWA 6963 to constrain its petrogenesis, including the depth of emplacement (i.e., base of a flow versus crustal intrusion).
NWA 6963 is an enriched shergottite with similar mineralogy to the basaltic shergottites, but importantly, does not contain any fine‐grained mesostasis. Consistent with the mineralogy, the reflectance (VNIR and TIR) spectrum of powdered NWA 6963 is similar to other shergottites because they are all dominated by pyroxene, but its reflectance is distinct in terms of albedo and spectral contrast due to its gabbroic texture. NWA 6963 represents a partial cumulate gabbro that is associated with the basaltic shergottites. Therefore, NWA 6963 could represent a hypabyssal intrusive feeder dike system for the basaltic shergottites that erupted on the surface.