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  • 1
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    Isolation and Monitoring of Cleanroom-Associated Microbial Contaminates From Geological Collections (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Microbial contamination is of particular interest to geological curation as many microorganisms can change mineral composition and produce compounds used as biosignatures used for the detection of life. Microbial cells can change the mineral composition of rocks through organic acid production and direct enzymatic oxidation/reduction of transition metals. Enzymatic oxidation of iron and manganese can occur at a rate several orders of magnitude faster than under abiotic conditions and produce highly reactive nanoparticle- sized oxides that can react and sorb other metals and organic compounds. Many fungi can also produce organic acids that dissolve and chelate mineral matrices chemically reducing and dissolving rock surfaces. Finally, several common soil-associated bacteria and fungi produce secondary metabolites that contain unusual amino acid analogs and non-ribosomal peptides containing both L- and D- chirality used in characterizing carbonaceous chondrites and the detection of extraterrestrial life.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-E-DAA-TN65757 , Lunar and Planetary Science Conference; Mar 18, 2019 - Mar 22, 2019; Woodlands, TX; United States
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  • 2
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    OSIRIS-REx Gravity Field Estimates for Bennu Using Spacecraft and Natural Particle Tracking Data (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-20
    Description: The current best estimates of Bennus gravity field will be presented, based on the independent solutions from four different teams involved on the OSIRIS-REx mission. The discovery of ejected particles about Bennu that may remain in orbit for several days or more provide a unique opportunity to probe the gravity field to higher degree and order than possible by using conventional spacecraft tracking. However, the non-gravitational forces acting on these particles must also be characterized, and their impact on solution accuracy must be assessed. This talk will present the latest results from the mission, incorporating spacecraft tracking from the lowest orbit in which the satellite will be during the mission.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN68580 , European Planetary Science Congress / Division for Planetary Sciences Joint Meeting (EPSC-DPS 2019); Sep 15, 2019 - Sep 20, 2019; Geneva; Switzerland
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  • 3
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    Episodes of Particle Ejection from the Surface of the Active Asteroid (101955) Bennu (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-04
    Description: Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and SecurityRegolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN76455 , Science (ISSN 0036-8075) (e-ISSN 1095-9203); 366; 6470; eaay3544
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  • 4
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    Pyroclastics Northeast of Gassendi Crater: Discovery/Characteristics/Implications (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In our ongoing effort to better understand lunar volcanism on the Moon, we are investigating pyroclastic deposits in the Gassendi region. Interest in pyroclastics has remained high due to the availability of high-resolution data (LRO, Kaguya), which is used to build on previous remote sensing studies [e.g., 1, 2, 3] and also extensive studies of lunar pyroclastic glasses [4, 5]. Analyses conducted in the laboratory of pyroclastic spheres from several deposits show that this volcanic material had a greater depth of origin and lesser fractional crystallization than mare basalts [e.g., 4, 6]. Data indicates that pyroclastic glasses are the best examples of primitive materials on the Moon, and they are important for both characterizing the lunar interior and as a starting place for under-standing the origin and evolution of lunar basaltic magmatism [2].
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-38868 , Lunar and Planetary Science Conference; Mar 20, 2017 - Mar 24, 2017; The Woodlands, TX; United States
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  • 5
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    Microstructural Constraints on the Formation History of Hibonite in Refractory Inclusions (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Hibonite is a primary refractory phase occurring in many Ca-Al-rich inclusions (CAIs), typically with spinel and perovskite [1]. Previous mi-crostructural studies of hibonite in CAIs revealed the presence of numerous stacking defects along the (001) plane and correlated non-stoichiometry in hibonite [2,3]. These features are interpreted as complex inter-growths of stoichiometric and Ca-deficient hibonites, as shown by experimental studies of reaction-sintered CaO-Al2O3 compounds [4]. Here, we extend our transmission electron microscope (TEM) studies to hibonite-bearing CAIs in CM chondrites that have been well characterized isotopically [5-7]. In addition, we have undertaken a series of anneal-ing experiments to explore the effect of minor elements (Mg and Ti) on the microstucure of hibonite [8,9,this study]. The results of these experiments are being applied to hibonite in CAIs in order to better understand its formation conditions.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-38853 , Lunar and Planetary Science Conference; Mar 20, 2017 - Mar 24, 2017; The Woodlands, TX; United States
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