IRIDIUM MEASUREMENTS. K. C. Welten1, A. J. Bixler1, K. Nishiizumi1, M. W. Caffee2, A. J. G. Jurewicz3, D.S. Woolum4, and D. S. Burnett5, 1Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA (kcwelten@ berkeley.edu), 2PRIME Laboratory, Purdue University, West Lafayette, IN 47907, USA; 3School of Earth & Space Exploration, Arizona State University, Tempe, AZ 85287, USA; 4Dept. of Physics, California State University, Fullerton, CA 92834, USA; 5Div. Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.

Solar abundances are important to planetary science since the prevalent model assumes that the composition of the solar photosphere is that of the solar nebula from which planetary materials formed. Thus, solar abundances are a baseline for planetary science. Previously, solar abundances have only been available through spectroscopy or by proxy (CI). The Genesis spacecraft collected and returned samples of the solar wind for laboratory analyses. Elemental and isotopic abundances in solar wind from Genesis samples have been successfully measured despite the crash of the re-entry capsule. Here we present science rationales for a set of 12 important (and feasible postcrash) Science and Measurement Objectives as goals for the future (Table 1). We also review progress in Genesis sample analyses since the last major review (Burnett 2013). Considerable progress has been made toward understanding elemental fractionation during the extraction of the solar wind from the photosphere, a necessary step in determining true solar abundances from solar wind composition. The suitability of Genesis collectors for specific analyses is also assessed. Thus far, the prevalent model remains viable despite large isotopic variations in a number of volatile elements, but its validity and limitations can be further checked by several Objectives.

Introduction: Solar wind (SW) Mg analyses of Genesis diamond-like carbon (DLC) on silicon (DoS) collectors give a fluence of 1.59E12 atoms/cm, with a +3.5% 1ơ standard deviation of 8 analyses. This fluence is consistent with measurements in silicon using both front-side [1] and backside [2] SIMS depth profiling. Ion yield and instrumental mass fractionation (IMF) under SIMS analysis are variable; this new method quantifies previously problematic analyses. Consistency of the SW Mg fluence from DoS and silicon collectors confirms retention of Mg in Genesis silicon despite radiation-induced segregation [3]; however, preliminary calculations using this new method suggest that this may not be the case for SW Na. Experimental: Two pieces of DoS were analyzed on the Cameca 6F at ASU. One DoS fragment was a flight-spare fragment implanted with Mg/Mg at a ICPMS-calibrated ratio of 0.975 and whose Mg fluence was determined to be 8.2E13 atoms/cm by SIMS analysis of co-implanted silicon. The other fragment was Genesis flight sample 20732,2. Details of the implantation, Mg/Mg calibration, and SIMS analyses – both instrument conditions and the variation of ion yield with matrix properties -are given in [4,5]. Variation of IMF with matrix properties are outlined in [5]. Methods: Background corrections (<<1% of total SW counts) were negligible. What is new is the method for recognizing and quantifying surface contamination and the resultant data reduction method used for determining the SW Mg fluence. Fig. 1 gives example corrections (previous and current) to a relatively clean SW Mg depth profile. The SRIM fit uses the SW velocity distribution measured in situ and does not require such a clean depth profile. All that is required is that a segment of the SW profile be clean of contamin ation. Fig. 2 gives an example SRIM fit correction

R Hervig3, G.R. Huss4, A.J.G. Jurewicz3, E.C. Koeman-Shields4, J.M. Laming5, K.D. McKeegan2, L. Nittler6, D. Reisenfeld7, K.D. Rieck8, J. Wang6, R.C. Wiens8, D.S. Woolum9 1Geological, Planetary Sciences, Caltech, Pasadena CA, 91125, burnett@gps.caltch.edu 2Earth, Planetary Sciences UCLA, Los Angeles CA, 90095. 3SESE, ASU, Tempe, AZ, 85287. 4HIGP, University of Hawai‘i at Mānoa, 1680 East-West Road, Honolulu, HI 96822. 5NRL Washington D.C., 20375. 6DTM, CIW, Washington D.C. 20015. 7Physics, U. Montana, Missoula, MT, 59812. 8Space and Remote Sensing (ISR-2), LANL, Los Alamos NM, 87545. 9Physics, CSUF, Fullerton CA 92831.

We compare element and isotopic fractionations measured in solar wind samples collected by NASA's Genesis mission with those predicted from models incorporating both the ponderomotive force in the chromosphere and conservation of the first adiabatic invariant in the low corona. Generally good agreement is found, suggesting that these factors are consistent with the process of solar wind fractionation. Based on bulk wind measurements, we also consider in more detail the isotopic and elemental abundances of O. We find mild support for an O abundance in the range 8.75 - 8.83, with a value as low as 8.69 disfavored. A stronger conclusion must await solar wind regime specific measurements from the Genesis samples.

The recovered Genesis collector fragments are heavily contaminated with crash-derived particulate debris. However, megasonic treatment with ultra-pure-water (UPW; resistivity (is) greater than18 meg-ohm-cm) removes essentially all particulate contamination greater than 5 microns in size [e.g.1] and is thus of considerable importance. Optical imaging of Si sample 60336 revealed the presence of a large C-rich particle after UPW treatment that was not present prior to UPW. Such handling contamination is occasionally observed, but such contaminants are normally easily removed by UPW cleaning. The 60336 particle was exceptional in that, surprisingly, it was not removed by additional UPW or by hot xylene or by aqua regia treatment. It was eventually removed by treatment with NH3-H2O2. Our best interpretation of the origin of the 60336 particle was that it was adhesive from the Post-It notes used to stabilize samples for transport from Utah after the hard landing. It is possible that the insoluble nature of the 60336 particle comes from interaction of the Post-It adhesive with UPW. An occasional bit of Post-It adhesive is not a major concern, but C particulate contamination also occurs from the heat shield of the Sample Return Capsule (SRC) and this is mixed with inorganic contamination from the SRC and the Utah landing site. If UPW exposure also produced an insoluble residue from SRC C, this would be a major problem in chemical treatments to produce clean surfaces for analysis. This paper reports experiments to test whether particulate contamination was removed more easily if UPW treatment was not used.

To maximize the scientific return of Genesis Solar Wind return mission it is necessary to characterize and remove a crash-derived particle and thin film surface contamination. A small subset of Genesis mission collector fragments are being subject-ed to extensive study via various techniques [1-6]. Here we present an update on the sample 60336, a Czochralski silicon (Si-CZ) based wafer from the bulk array (B/C).

D. S. Woolum , K. D. McKeegan , V. Heber , Y. Guan 2 , M. Humayun, and R. Hervig, 1 Center for Meteorite Studies, Arizona State University, Tempe AZ 85287, Geological and Planetary Sciences, Caltech m/s 100-23, Pasadena CA 91125, 3 Department of Physics, CSUF, Fullerton CA 92831, 4 Earth and Space Sciences, UCLA, Los Angeles, CA 90095-1567, National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310 (contacts: burnett@gps.caltech.edu or Amy.Jurewicz@asu.edu ).

Quantitative understanding of solar wind (SW) elemental fractionation is required to improve knowledge of the solar nebula abundances from Genesis samples, in particular abundances of volatile elements, depleted in CI chondrites. Ratios of elements with low and high first ionization potential (FIP) in the solar wind, e.g., Fe/He, are higher than photospheric abundances. C, O, and N have intermediate FIP and are thus critical as to whether this fractionation is stepwise or gradual as a function of FIP.

SOLAR-WIND FIP FRACTIONATION, AND COMPARISONS WITH CI CHONDRITES. A. J. G. Jurewicz , D. S. Burnett , D. S. Woolum , K. D. McKeegan , Y. Guan 2 , and R. Hervig , 1 Center for Meteorite Studies, Arizona State University, Tempe AZ 85287, Geological and Planetary Sciences, Caltech m/s 100-23, Pasadena CA 91125, 3 Department of Physics, UC Fullerton, Fullerton CA, 3 Earth and Space Sciences m/c GE-75, UCLA, Los Angeles, CA 90095-1567 (contacts: Amy.Jurewicz@asu.edu or burnett@gps.caltech.edu ).

Solar wind elemental abundances are a major Genesis science objective. Spacecraft studies have shown that elements with first ionization potential (FIP) > 9 eV are fractionated relative to those with lower FIP compared with the solar photosphere; however, among elements with FIP < 9eV (which make up most of the terrestrial planets) there is no evidence of fractionation. A major goal of Genesis is to provide a higher precision test of the lack of fractionation for FIP < 9eV.

Introduction: Elemental abundances, specifically Fe and Mg fluences, are being measured in selected collector fragments. This study is in pursuit of one of the first goals for the analysis of Genesis samples: measuring the magnitudes of fractionation of solar wind elemental abundances relative to the solar photosphere, especially as a function of elemental First Ionization Potential (FIP) and First Ionization Time (FIT). The relative abundances of elements with FIP below 9 eV (Fig. 1) are of particular interest as they appear unfractionated in spacecraft data, but in situ measurements are imprecise relative to those expected from analyzing Genesis collectors. In contrast, ele-

To meet the Genesis mission goal for improved solar elemental abundances, we need to address the issue of fractionation of the abundances of elements in the solar wind compared to the solar photosphere. There is a well-established depletion of elements in the solar wind with high first ionization potential (FIP > 9eV) compared to lower FIP elements, but there is no evidence for fractionation between lower FIP elements.