^1,2Selby Cull, ^2,3Patrick C. McGuire, ²Christoph Gross, ¹Jenna Myers, ¹Nina Shmorhun
¹Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, USA
²Planetary Sciences and Remote Sensing Group, Institute of Geological Sciences, Department of Earth Sciences, Freie Universitaet Berlin, Berlin 12249, Germany
³Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland 20723, USA

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Reference
Cull S, McGuire PC, Gross C, Myers J, Shmorhun N (2014) A new type of jarosite deposit on Mars: Evidence for past glaciation in Valles Marineris? Geology 42, 59-962
Link to Article [doi:10.1130/G36152.1]

¹David W. Mittlefehldt
¹XI3/Astromaterials Research Office, Astromaterials Research and Exploration Sciences Division, NASA/Johnson Space Center, 2101 NASA Parkway, Houston, TX 77058, USA

The howardite, eucrite and diogenite (HED) clan of meteorites are ultramafic and mafic igneous rocks and impact-engendered fragmental debris derived from a thoroughly differentiated asteroid. Earth-based telescopic observation and data returned from vestan orbit by the Dawn spacecraft make a compelling case that the asteroid (4) Vesta is the parent asteroid of HEDs, although this is not universally accepted. Diogenites are petrologically diverse and include dunitic, harzburgitic and noritic lithologic types in addition to the traditional orthopyroxenites. Diogenites form the lower crust of Vesta. Cumulate eucrites are gabbroic rocks formed by accumulation of pigeonite and plagioclase from a mafic magma at depth within the crust, while basaltic eucrites are melt compositions that likely represent shallow-level dikes and sills, and flows. Some basaltic eucrites are richer in incompatible trace elements compared to most eucrites, and these may represent mixed melts contaminated by partial melts of the mafic crust. Differentiation occurred within a few Myr of formation of the earliest solids in the Solar System. Evidence from oxygen isotope compositions and siderophile element contents favor a model of extensive melting of Vesta forming a global magma ocean that rapidly (period of a few Myr) segregated and crystallized to yield a metallic core, olivine-rich mantle, orthopyroxene-rich lower crust and basaltic upper crust. The igneous lithologies were subjected to post-crystallization thermal processing, and most eucrites show textural and mineral-compositional evidence for metamorphism. The cause of this common metamorphism is unclear, but may have resulted from rapid burial of early basalts by later flows caused by high effusion rates on Vesta. The observed surface of Vesta is covered by fragmental debris resulting from impacts, and most HEDs are brecciated. Many eucrites and diogenites are monomict breccias indicating a lack of mixing. However, many HEDs are polymict breccias. Howardites are the most thoroughly mixed polymict breccias, yet only some of them contain evidence for residence in the true regolith. Based on the numbers of meteorites, compositions of howardites, and models of magma ocean solidification, cumulate eucrites and their residual ferroan mafic melts are minor components of the vestan crust.

Reference
Mittlefehldt DW (2014) Asteroid (4) Vesta: I. The howardite-eucrite-diogenite (HED) clan of meteorites. Chemie der Erde (in Press)
Link to Article [doi:10.1016/j.chemer.2014.08.002]

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^1,2János Kovacs,²István Sajó, ^3,4Zsuzsanna Márton, ^1,2Viktor Jáger, ⁵Tibor Hegedüs, ⁶Tibor Berecz, ⁴Tamás Tóth, ⁷Péter Gyenizse, ^1,2András Podobni
¹Department of Geology and Meteorology, University of Pécs, H-7624 Pécs, Ifjúság u. 6, Hungary
²Environmental Analytical and Geoanalytical Research Group, Szentágothai Research Centre, University of Pécs, H-7624 Pécs, Ifjúság u. 20, Hungary
³MTA-PTE High-Field Terahertz Research Group, H-7624, Pécs Ifjúság u. 6, Hungary
⁴Institute of Physics, University of Pécs, H-7624, Pécs Ifjúság u. 6, Hungary
⁵Baja Astronomical Observatory, H-6500 Baja, POB 766, Hungary
⁶Department of Materials Science and Engineering, Budapest University of Technology and Economics, H-1111 Budapest, Bertalan L. u. 7, Hungary
⁷Department of Cartography and Geoinformatics, University of Pécs, H-7624 Pécs, Ifjúság u. 6, Hungary

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Reference
Kovacs J, István Sajób, Márton Z, Jáger V, Hegedüs T, Berecz T, Tóth T, Gyenizse P, Podobni A (2014) Csátalja, the largest H4-5 chondrite from Hungary. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2014.11.009]

¹M.C. De Sanctis, ¹A. Frigeri, ^1,2E. Ammannito, ¹F. Tosi, ^1,3S. Marchi, ¹F. Zambon, ⁴C.A. Raymond, ²C.T. Russell
¹INAF, Istituto di Astrofisica e Planetologia Spaziali, Area di Ricerca di Tor Vergata, 00133 Roma, Italy
²Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, USA
³SSERVI Southwest Research Institute, 1050 Walnut St, Suite 300, Boulder, CO 80302
⁴Jet Propulsion Laboratory, Pasadena, CA 91109, USA

The young Marcia crater on Vesta displays several interesting features, including pitted and smooth terrains, exposure of relatively bright and dark material, and enrichments of hydrated material in the ejecta. Several questions arise about the origin of Marcia and of the dark material (exogenic material versus volcanic or impact melts) and the smooth and pitted terrains. Here we describe the results of the spectral and thermal analysis of the Marcia crater, with a particular effort to assess the composition of the different units, identifying the presence of OH and its correlation with dark material. Detailed studies of the Marcia crater wall, smooth and floor units reveal a compositional rich terrain with small areas enriched in diogenites with respect to the general eucritic regolith dominating the equatorial region of Vesta. The signature of OH is particularly clear in the pitted floor, dark material, smooth unit, and ejecta. The pitted terrains, beside their appearance, also show thermal anomalies, being colder with respect to the surrounding terrains. The presence of OH, concentrated in darker layers, and the pitted crater floor indicate that the area where the Marcia impact event occurred was rich in volatiles. The results show how the relatively young impact events have modified the surface of Vesta, disrupting a layer of dark material once present on Vesta’s equatorial terrain and exposing fresh, bright material rich in pyroxene.

Reference
De Sanctis MC, Frigeri A, Ammannito E, Tosi F, Marchi S, Zambon F, Raymond CA, Russell CT (2014) Mineralogy of Marcia, the youngest large crater of Vesta: Character and distribution of pyroxenes and hydrated material. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2014.10.051]

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