¹Yamamoto S. et al.(>10)*
¹Center for Environmental Measurement and Analysis, National Institute for Environmental Studies, Tsukuba, Japan
*Find the extensive, full author and affiliation list on the publishers website

We present details of the global distribution of high-Ca pyroxene (HCP)-rich sites in the lunar highlands based on the global dataset of hyper-spectral reflectance obtained by the SELENE Spectral Profiler. Most HCP-rich sites in the lunar highlands are found at fresh impact craters. In each crater, most of the detection points are distributed on the ejecta, rim, and floor of the impact craters rather than the central peaks, while the central peaks are dominated by purest anorthosite (PAN). This indicates that HCP-rich materials originate from relatively shallower regions of the lunar crust than PAN. In addition, while all ray craters with sizes larger than ~40km possess HCP-rich materials, small fresh craters with sizes less than ~6−−10km do not, indicating that the uppermost mixing layers in the lunar crust are not dominated by HCP. Based on these results, we propose that in the upper lunar crust, a HCP-rich zone overlying the PAN layer exists below the uppermost mixing layer. This HCP-rich zone may originate from interstitial melt during the formation of the flotation anorthositic cumulate, while an impact ejecta origin, impact melt origin, and/or magmatic intrusion into the upper lunar crust may also account for the occurrence of HCP-rich sites in the highlands.

Reference
Yamamoto S et al. (2015) Global occurrence trend of high-Ca pyroxene on lunar highlands and its implications. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004740]

Published by arrangement with John Wiley&Sons

^1,2E.C. Sklute, ¹H.B.Jensen, ¹A.D. Rogers, ¹R.J.
Reeder
¹Stony Brook University, Department of Geosciences, Stony Brook, NY 11794-2100, USA
²Mount Holyoke College, Department of Astronomy, South Hadley, MA

Current or past brine hydrologic activity on Mars may provide suitable conditions for the formation of amorphous ferric sulfates. Once formed, these phases would likely be stable under current Martian conditions, particularly at low- to mid-latitudes. Therefore, we consider amorphous iron sulfates (AIS) as possible components of Martian surface materials. Laboratory AIS were created through multiple synthesis routes, and characterized with total x-ray scattering, thermogravimetric analysis, scanning electron microscopy, visible/near-infrared (VNIR), thermal infrared (TIR), and Mössbauer techniques. We synthesized amorphous ferric sulfates (Fe(III)2(SO4)3•~6-8H2O) from sulfate-saturated fluids via vacuum dehydration or exposure to low relative humidity (<11%). Amorphous ferrous sulfate (Fe(II)SO4•~1H2O) was synthesized via vacuum dehydration of melanterite. All AIS lack structural order beyond 11 Å. The short-range (<5 Å) structural characteristics of amorphous ferric sulfates resemble all crystalline reference compounds; structural characteristics for the amorphous ferrous sulfate are similar to but distinct from both rozenite and szomolnokite. VNIR and TIR spectral data for all AIS display broad, muted features consistent with structural disorder and are spectrally distinct from all crystalline sulfates considered for comparison. Mössbauer spectra are also distinct from crystalline phase spectra available for comparison. AIS should be distinguishable from crystalline sulfates based on the position of their Fe-related absorptions in the visible range and their spectral characteristics in the TIR. In the NIR, bands associated with hydration at ~1.4 and 1.9 µm are significantly broadened, which greatly reduces their detectability in soil mixtures. AIS may contribute to the amorphous fraction of soils measured by the Curiosity rover.

Reference
Sklute EC, Jensen HB, Rogers AD, Reeder RJ (2015) Morphological, Structural, and Spectral Characteristics of Amorphous Iron Sulfates. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004784]

Published by arrangement with John Wiley&Sons

¹Steven J. Jaret, ¹William R. Woerner, ¹Brian L. Phillips, ^2,3Lars Ehm¹Hanna Nekvasil, ^4,5Shawn P. Wright, ¹TimothyD.Glotch
¹Department of Geosciences, State University of New York at Stony Brook, Stony Brook, New York, USA,
²Mineral Physics Institute, State University of New York at Stony Brook, Stony Brook, New York, USA,
³Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York, USA,
⁴Department of Geosciences, Auburn University, Auburn, Alabama, USA,
⁵Planetary Science Institute, Tucson, Arizona, USA

We present the results of a combined study of shocked labradorite from the Lonar crater, India, using optical microscopy, micro-Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, high-energy X-ray total scattering experiments, and micro-Fourier transform infrared (micro-FTIR) spectroscopy. We show that maskelynite of shock class 2 is structurally more similar to fused glass than to crystalline plagioclase. However, there are slight but significant differences—preservation of original preimpact igneous zoning, anisotropy at infrared wavelengths, X-ray anisotropy, and preservation of some intermediate range order—which are all consistent with a solid-state transformation from plagioclase to maskelynite.

Jaret SJ, Woerner WR, Phillips BL, Ehm L, Nekvasil H, Wright SP, Glotch TD (2015) Maskelynite formation via solid-state transformation: Evidence of infrared and X-ray anisotropy. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004764]

Published by arrangement with John Wiley&Sons