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  • 1
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    Surface and Atmospheric Contributions to Passive Microwave Brightness Temperatures for Falling Snow Events (2011)
    In:  Other Sources
    Details
    Publication Date: 2018-06-05
    Description: Physically based passive microwave precipitation retrieval algorithms require a set of relationships between satellite -observed brightness temperatures (TBs) and the physical state of the underlying atmosphere and surface. These relationships are nonlinear, such that inversions are ill ]posed especially over variable land surfaces. In order to elucidate these relationships, this work presents a theoretical analysis using TB weighting functions to quantify the percentage influence of the TB resulting from absorption, emission, and/or reflection from the surface, as well as from frozen hydrometeors in clouds, from atmospheric water vapor, and from other contributors. The percentage analysis was also compared to Jacobians. The results are presented for frequencies from 10 to 874 GHz, for individual snow profiles, and for averages over three cloud-resolving model simulations of falling snow. The bulk structure (e.g., ice water path and cloud depth) of the underlying cloud scene was found to affect the resultant TB and percentages, producing different values for blizzard, lake effect, and synoptic snow events. The slant path at a 53 viewing angle increases the hydrometeor contributions relative to nadir viewing channels. Jacobians provide the magnitude and direction of change in the TB values due to a change in the underlying scene; however, the percentage analysis provides detailed information on how that change affected contributions to the TB from the surface, hydrometeors, and water vapor. The TB percentage information presented in this paper provides information about the relative contributions to the TB and supplies key pieces of information required to develop and improve precipitation retrievals over land surfaces.
    Keywords: Geophysics
    Type: Journal of Geophysical Research - Atmospheres; Volume 116; D02213
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  • 2
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    Actinide crystal-liquid partitioning for clinopyroxene and Ca3/PO4/2 (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Coefficients for the partitioning of the actinide elements Th, U and Pu, which are used as indicators of r-process nucleosynthesis and the ages of meteorite and lunar samples, between diopsidic clinopyroxene, whitlockite and silicate liquid at 20 kbar are measured. Fission and alpha track radiography techniques are employed to detect element concentrations in synthetic crystals made using spiked starting materials, under the assumptions of equilibrium partitioning at the crystal-liquid interface and actinide zoning. Analysis of the data indicates results to be consistent with interface equilibrium except at high cooling rates. Th/U/Pu partition coefficients of about 0.002/0.002/O.06 are measured for clinopyroxene and 1.2/0.5/3.4 for whitlockite. The greater incorporation of Pu into the crystalline phases is attributed to the importance of trivalent Pu, and the similarity of its partition coefficient into clinopyroxene to that of the light rare earths supports the concept of Pu/rare earth dating.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 44; Sept
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  • 3
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    Laboratory actinide partitioning - Whitlockite/liquid and influence of actinide concentration levels (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The partition coefficients between synthetic whitlockite (beta Ca-phosphate) and coexisting silicate melts are determined for the actinide elements Th, U and Pu. Experiments were performed at 1 bar pressure and 1250 C at oxygen fugacities from 10 to the -8.5 to 10 to the -0.7 bars, and partitioning was determined from trace element radiography combined with conventional electron microprobe analysis. Results show Pu to be more readily incorporated into crystalline phases than U or Th under reducing conditions, which is attributed to the observation that Pu exists primarily in the trivalent state, while U and Th are tetravalent. Corrected partition coefficients for whitlockite of 3.6, less than or equal to 0.6, 1.2, 0.5 and less than or equal to 0.002 are estimated for Pu(+3), Pu(+4), Th(+4), U(+4) and U(+6), respectively. Experiments performed at trace levels and percent levels of UO2 indicate that Si is involved in U substitution in whitlockite, and show a reduced partition coefficient at higher concentrations of U that can be explained by effects on melt structure or the fraction of tetravalent U.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 47; 1695-170
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  • 4
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    Pyroclastic Deposits in Floor-Fractured Craters: A Unique Style or Lunar Basaltic Volcanism? (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The lunar maria were formed by effusive fissure flows of low-viscosity basalt. Regional pyroclastic deposits were formed by deep-sourced fire-fountain eruptions dominated by basaltic glass. Basaltic material is also erupted from small vents within floor-fractured impact craters. These craters are characterized by shallow, flat floors cut by radial, concentric and/or polygonal fractures. Schultz [1] identified and classified over 200 examples. Low albedo pyroclastic deposits originate from depressions along the fractures in many of these craters.
    Keywords: Geophysics
    Type: JSC-CN-27805 , Lunar and Planetary Science Institute Conference; Mar 18, 2013 - Mar 22, 2013; The Woodlands, TX; United States
    Format: application/pdf
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  • 5
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    Derivation of FEO Abundances in Lunar Pyroclastic Deposits Using Diviner (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Telescopic observations and orbital images of the Moon reveal at least 75 lunar pyroclastic deposits (LPDs), interpreted as the products of explosive volcanic eruptions [1]. The deposits are understood to be composed primarily of sub-millimeter beads of basaltic composition, ranging from glassy to partially-crystallized [2]. Delano [3] documented 25 distinct pyroclastic bead compositions in lunar soil samples, with a range of FeO abundances from 16.5 - 24.7 wt%. Green glasses generally have lower FeO abundances and red, yellow, and orange glasses generally have higher FeO abundances. The current study employs data from the Diviner Lunar Radiometer Experiment onboard the Lunar Reconnaissance Orbiter (LRO) to derive the FeO compositions of glasses from unsampled lunar pyroclastic deposits. The pyroclastic glasses are the deepest-sourced and most primitive basalts on the Moon [4]. Recent analyses have documented the presence of water in these glasses, demonstrating that the lunar interior is considerably more volatile-rich than previously understood [5]. Experiments have shown that the iron-rich pyroclastic glasses release the highest percentage of oxygen of any Apollo soils, making these deposits promising lunar resources [6].
    Keywords: Geophysics
    Type: JSC-CN-25614 , 43rd Lunar aud Plauetary Science Conference; Mar 19, 2012 - Mar 23, 2012; The Woodlands, TX; United States
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  • 6
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    A test of the smoothness of the elemental abundances of carbonaceous chondrites (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Analyses of several carbonaceous chondrites (including the Orgueil samples 626, 629, and 630; and Ivuna samples 627, 628, and 631) for elements from Fe through Ru were performed using proton-induced X-rays, in order to test the smoothness of the elemental abundances in these chondrites. In general, the results confirm previously published abundance curves. The abundances were exceptionally smooth and strongly decreasing in the mass region 60-75. From the mass number 75 to 101, a smooth curve could be drawn, within limits of intersample variability, except for Y peak. Over the whole periodic table, a large number of peaks of probable nucleosynthetic origin could be identified.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 53; 471-481
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  • 7
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    Experimental partitioning studies near the Fe-FeS eutectic, with an emphasis on elements important to iron meteorite chronologies (Pb, Ag, Pd, and Tl) (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Partitioning coefficients for metal/sulfide liquid, troilite/sulfide liquid, and schreibersite/sulfide liquid were determined for Ag, Au, Mo, Ni, Pd, and Tl (using EMPA and proton-induced X-ray microprobe and ion microprobe analyses) in order to understand the chronometer systems of iron meteorites. In general, the obtained schreibersite/metal and troilite/metal partition coefficients for 'compatible' elements were quite similar to those inferred from natural assemblages, reinforcing an earlier made conclusion that there is a class of elements for which experimental troilite/metal and schreibersite/metal partition coefficients approximate those inferred from natural samples. The consistency between experimental and natural assemblages, however, was not observed for Ag, Pb, and Tl, indicating that the abundances of these elements determined in 'metal' and 'troilite' separates from iron meteorites are influenced by trace minerals that concentrate incompatible elements.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 57; 2; p. 453-460.
    Format: text
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