José M Madied¹

¹Facultad de Ciencias Experimentales, Universidad de Huelva, Huelva 21071, Spain

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Reference

Madied JM (2014) Robotic systems for the determination of the composition of solar system materials by means of fireball spectroscopy. Earth, Planets and Space 66, 70

Link to Article [doi:10.1186/1880-5981-66-70]

M.Nachon¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Laboratoire de Planétologie et Géodynamique de Nantes, CNRS, UMR6112, Université de Nantes, Nantes, France

The Curiosity rover has analyzed abundant light-toned fracture-fill material within the Yellowknife Bay sedimentary deposits. The ChemCam instrument, coupled with Mastcam and ChemCam/Remote Micro Imager images, was able to demonstrate that these fracture fills consist of calcium sulfate veins, many of which appear to be hydrated at a level expected for gypsum and bassanite. Anhydrite is locally present, and is found in a location characterized by a nodular texture. An intricate assemblage of veins crosses the sediments, which were likely formed by precipitation from fluids circulating through fractures. The presence of veins throughout the entire ~5 m thick Yellowknife Bay sediments suggests that this process occurred well after sedimentation and cementation/lithification of those sediments. The sulfur-rich fluids may have originated in previously precipitated sulfate-rich layers, either before the deposition of the Sheepbed mudstones, or from unrelated units such as the sulfates at the base of Mount Sharp. The occurrence of these veins after the episodes of deposition of fluvial sediments at the surface suggests persistent aqueous activity in relatively non-acidic conditions.

Reference

Nachon M, Clegg SM, Mangold N, Schröder S, Kah LC, Dromart G, Ollila A, Johnson JR, Oehler DZ, Bridges JC et al. (Accepted) Calcium sulfate veins characterized by ChemCam/Curiosity at Gale Crater, Mars
Journal of Geophysical Research: Planets 2169-9100

Link to Article [DOI: 10.1002/2013JE004588]

Published by arrangement with John Wiley & Sons

T.C. Prissel, S.W. Parman, C.R.M. Jackson, M.J. Rutherford, P.C. Hess, J.W. Head, L. Cheek, D. Dhingra, C.M. Pieters

Department of Earth, Environmental & Planetary Sciences, Brown University, Providence, RI 02912, USA

NASA’s Moon Mineralogy Mapper (M³) has identified and characterized a new lunar rock type termed pink spinel anorthosite (PSA) (Pieters et al., 2011). Dominated by anorthitic feldspar and rich in MgAl₂O₄ spinel, PSA appears to have an unusually low modal abundance of mafic silicates, distinguishing it from known lunar spinel-bearing samples. The interaction between basaltic melts and the lunar crust and/or assimilation of anorthitic plagioclase have been proposed as a possible mechanism for PSA formation (Gross and Treiman, 2011 and Prissel et al., 2012). To test these hypotheses, we have performed laboratory experiments exploring magma–wallrock interactions within the lunar crust. Lunar basaltic melts were reacted with anorthite at 1400 °C and pressures between 0.05–1.05 GPa. Results indicate that PSA spinel compositions are best explained via the interaction between Mg-suite parental melts and anorthositic crust. Mare basalts and picritic lunar glasses produce spinels too rich in Fe and Cr to be consistent with the M³ observations.
The experiments suggest that PSA represents a new member of the plutonic Mg-suite. If true, PSA can be used as a proxy for spectrally identifying areas of Mg-suite magmatism on the Moon. Moreover, the presence of PSA on both the lunar nearside and farside (Pieters et al., in press) indicates Mg-suite magmatism may have occurred on a global scale. In turn, this implies that KREEP is not required for Mg-suite petrogenesis (as KREEP is constrained to the nearside of the Moon) and is only necessary to explain the chemical make-up of nearside Mg-suite samples.

Reference
Prissel TC, Parman SW, Jackson CRM, Rutherford MJ, Hess PC, Head JW, Cheek L, Dhingra D and Pieters CM (in press) Pink Moon: The petrogenesis of pink spinel anorthosites and implications concerning Mg-suite magmatism. Earth and Planetary Science Letters 403:144.
[doi:10.1016/j.epsl.2014.06.027]
Copyright Elsevier

Link to Article

Alexander Hubbard

Department of Astrophysics, American Museum of Natural History, New York, NY 10024-5192, USA

In protoplanetary disks, dust grains rich in metallic iron can attract each other magnetically. If they are magnetized to values near saturation, the magnetically induced collision speeds are high enough to knock off the non-magnetized, loosely bound silicates. This process enriches the surviving portions of the dust grains in metallic iron, which further enhances the magnetically mediated collisions. The magnetic enhancement to the collisional cross-section between the iron rich dust results in rapid grain growth leading to planetesimal formation. While this process of knocking off silicates, which we term “magnetic erosion”, occurs only in a very limited portion of a protoplanetary disk, it is a possible explanation for Mercury’s disproportionately large iron core.

Reference
Hubbard A (in press) Explaining Mercury’s Density through Magnetic Erosion. Icarus
[doi:10.1016/j.icarus.2014.06.032]
Copyright Elsevier

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