ALBERT

Description: Oxygen fugacity plays an important role in determining the detailed physical and chemical aspects of planets and their building blocks. Basic chemical properties such as the amount of oxidized Fe in a mantle (as FeO), the nature of alloying elements in the core (S, C, H, O, Si), and the solubility of various volatile elements in the silicate and metallic portions of embryos and planets can influence physical properties such as the size of the core, the liquidus and solidus of the mantle and core, and the speciation of volatile compounds contributing to atmospheres. This paper will provide an overview of the range of fO2 variation observed in primitive and differentiated materials that may have participated in accretion (cosmic dust, Star-dust and meteorites), a comparison to observations of planetary fO2 (Mercury, Mars and Earth), and a discus-sion of timing of variation of fO2 within both early and later accreted materials. This overview is meant to promote discussion and interaction between students of these two stages of planet formation to identify areas where more work is needed.

Description: The abundances of volatile elements in the Earth's mantle are correlated with their temperatures of condensation. This depletion can be due to either incomplete condensation of the elements during the nebula condensation or evaporation processes during planetary growth. Elements that have affinities with metals (siderophile) and sulfides (chalcophile) are additionally depleted due to their segregation into the core. Therefore, study of lithophile elements could be useful to isolate processes of volatilization and their effect on the abundance of the elements in the Earth's mantle. However, the correlation of these lithophile elements including alkali elements, with their temperatures of condensation shows a significant scatter, which is difficult to reconcile with a depletion by vaporization or incomplete condensation alone.

Description: Igneous and metamorphic rocks commonly contain a mineral assemblage that allows oxygen fugacity to be calculated or constrained such as FeTi oxides, olivine-opx-spinel, or some other oxybarometer [1]. Some rocks, however, contain a limited mineral assemblage and do not provide constraints on fO2 using mineral equilibria. Good examples of the latter are orthopyroxenites or dunites, such as diogenites, ALH 84001, chassignites, or brachinites. In fact it is no surprise that the fO2 of many of these samples is not well known, other than being "reduced" and below the metal saturation value. In order to bridge this gap in our understanding, we have initiated a study of V in chromites in natural meteorite samples. Because the V pre-edge peak intensity and energy in chromites varies with fO2 (Fig. 1) [2], and this has been calibrated over a large fO 2 range, we can apply this relation to rocks for which we otherwise have no fO2 constraints.

Description: Achondritic meteorites are a diverse group of meteorites that formed by igneous activity in asteroids. These meteorites can provide important information about early differentiation processes on asteroidal bodies. The howardite-eucrite-diogenite (HED) meteorites, the largest group of achondrites, are the only group of meteorites for which a potential parent body has been identified (4 Vesta) [e.g., 1]. Mesosiderites are stony-iron meteorites composed of roughly equal amounts of metal and silicates and silicates are broadly similar to HED meteorites [2]. They may have been formed by impact-mixing of crustal and core materials of differentiated meteorite parent bodies. Chemical and oxygen isotopic compositional data suggest that the HED meteorites and silicate portions of mesosiderites originated on the same or closely related parent bodies. Pallasites and IIIAB irons also have similar oxygen isotope compositions and have been thought to be related to the HEDs [3,4]. However, recent high resolution analyses have shown that pallasites and HED's have different oxygen isotopic values, but mesosiderites and HED s have the same isotope compositions implying a close connection [5]. QUE 93148 is a small (1.1g) olivine-rich (mg 86) achondrite that contains variable amounts of orthopyroxenene (mg 87) and kamacite (6.7 wt% Ni), with minor augite [6]. This meteorite was originally classified as a lodranite [7], but it s oxygen isotopic composition precludes a genetic relationship to the acapulcoites and lodranites. And also this meteorite has a lower Mn/Mg ratio than any major group of primitive or evolved achondrites and suggested that QUE 93148 may be a piece of the deep mantle of the HED parent body [6]. To better understand the relationship between HED s, mesosiderites and related achondrites, we have measured trace elements in the individual metallic and silicate phases. In this study, abundances of a suite of elements were measured for the unusual mesosiderite RKPA 79015 and a ungrouped achondrite QUE93148.

Description: The New Frontiers mission, OSIRIS-REx, will encounter carbonaceous asteroid 101955 Bennu (1999 RQ36; [1]) in 2018, collect a sample and return it to Earth and deliver it to NASA-JSC for curation in 2023. The mission curation plan is being developed and an overview will be given, including the main elements of contamination control, sample recovery, cleanroom construction, and curation support once the sample is returned to Earth.