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NASA Technical Reports Server (NTRS) (685.125 recursos)

The NTRS is a valuable resource for students, educators, researchers, and the public for access to NASA's current and historical technical literature since it was first released in 1994. NTRS provides access to approximately 500K aerospace related citations, 90K full-text online documents, and 111K images and videos. NTRS numbers continues to grow over time as new scientific and technical information (STI) is created or funded by NASA. The type of information found in NTRS include: conference papers, images, journal articles, photos, meeting papers, movies, patents, research reports, and technical videos.

Mostrando recursos 121 - 140 de 320.544

  1. Space Weathering Experiments on Spacecraft Materials

    Cooper, R.; Plis, Elena; Cowardin, H.; Hoffman, R.; Engelhar, D.
    A project to investigate space environment effects on specific materials with interest to remote sensing was initiated in 2016. The goal of the project is to better characterize changes in the optical properties of polymers and Mylar, specifically those found in multi-layered spacecraft insulation, due to electron bombardment. Previous analysis shows that chemical bonds break and potentially reform when exposed to high energy electrons. Among other properties these chemical changes altered the optical reflectance as documented in laboratory analysis. This paper presents results of the initial experiment results focused on the exposure of materials to various fluences of high energy...

  2. Nitrogen on Mars: Insights from Curiosity

    Glavin, D. P.; Jackson, W. A.; Navarro-Gonzalez, Rafael; Stern, J. C.; Archer, P. Douglas; Ming, W.; Sutter, B.; Mahaffy, Paul R.; McKay, Chrisopher P.; Fairen, A. G.
    Recent detection of nitrate on Mars indicates that nitrogen fixation processes occurred in early martian history. Data collected by the Sample Analysis at Mars (SAM) instrument on the Curiosity Rover can be integrated with Mars analog work in order to better understand the fixation and mobility of nitrogen on Mars, and thus its availability to putative biology. In particular, the relationship between nitrate and other soluble salts may help reveal the timing of nitrogen fixation and post-depositional behavior of nitrate on Mars. In addition, in situ measurements of nitrogen abundance and isotopic composition may be used to model atmospheric conditions...

  3. Constraints on the Mineralogy of Gale Crater Mudstones from MSL SAM Evolved Water

    Archer, P. D.; Andrejkovicova, S.; Eigenbrode, J. L.; Ming, D. W.; Sutter, B.; Knudson, C. A.; Mahaffy, P. R.; Hogancamp, J. V. (Clark); McAdam, A. C.; Franz, H. B.
    The Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments on the Mars Science Laboratory (MSL) have analysed more than 150 micron fines from 14 sites at Gale Crater. Here we focus on the mudstone samples. Two were drilled from sites John Klein (JK) and Cumberland (CB) in the Sheepbed mudstone. Six were drilled from Murray Formation mudstone: Confidence Hills (CH), Mojave (MJ), Telegraph Peak (TP), Buckskin (BK), Oudam (OU), Marimba (MB). SAM's evolved gas analysis mass spectrometry (EGA-MS) detected H2O, CO2, O2, H2, SO2, H2S, HCl, NO, and other trace gases, including organic fragments. The identity and...

  4. Valence State Partitioning of Cr and V Between Olivine-Melt and Pyroxene-Melt in Experimental Basalts of a Eucritic Composition

    Le, L.; Karner, J. M.; Jones, J. H.
    The partitioning of multivalent elements in basaltic systems can elucidate the oxygen fugacity (fO2) conditions under which basalts formed on planetary bodies (Earth, Moon, Mars, asteroids). Chromium and V are minor and trace elements in basaltic melts, partition into several minerals that crystallize from basaltic melts, exist in multiple valence states at differing fO2 conditions, and can therefore be used as oxybarometers for basaltic melts. Chromium is mostly 3+ in terrestrial basaltic melts at relatively high fO2 values ( IW+3.5), and mostly 2+ in melts at low fO2 values ( IW-1), such as those on the Moon and some asteroids....

  5. Status of the Redesign of the Extravehicular Mobility Unit Airlock Cooling Loop Recovery Assembly

    Peyton, Barbara; Arnold, Dane; Steele, John; Rector, Tony; Jennings, Mallory
    During EVA (Extravehicular Activity) 23 aboard the ISS (International Space Station) on 07/16/2013 an episode of water in the EMU (Extravehicular Mobility Unit) helmet occurred, necessitating a termination of the EVA (Extravehicular Activity) shortly after it began. The root cause of the failure was determined to be ground-processing short-comings of the ALCLR Ion Beds which led to various levels of contaminants being introduced into the Ion Beds before they left the ground. The Ion Beds were thereafter used to perform on-orbit routine scrubbing operations for the EMU cooling water loop which led to the failure. The root cause investigation identified...

  6. A New Type of Foreign Clast in A Polymict Ureilite: A CAI or AL-Rich Chondrule

    Goodrich, C. A.; Treiman, A. H.; Ross, D. K.
    Introduction: Polymict ureilites are breccias interpreted to represent regolith formed on a ureilitic asteroid [1-3]. They consist of approximately 90-95% clasts of various ureilite types (olivine-pyroxene rocks with Fo 75-95), a few % indigenous feldspathic clasts, and a few % foreign clasts [4-20]. The foreign clasts are diverse, including fragments of H, L, LL and R chondrites, angrites, other achondrites, and dark clasts similar to CC [6,7,9-19]. We report a new type of foreign clast in polymict ureilite DaG 999. Methods: Clast 8 in Dar al Gani (DaG) 999/1 (Museum fur Naturkunde) was discovered during a survey of feldspathic clasts...

  7. Ion Microprobe Measurements of Comet Dust and Implications for Models of Oxygen Isotope Heterogeneity in the Solar System

    Messenger, S.; McKeegan, K. D.; Snead, C. J.; Keller, L. P.
    The oxygen isotopic compositions of anhydrous minerals in carbonaceous chondrites reflect mixing between a O-16-rich and O-17, O18-rich reservoir. The UV photodissociation of CO (i.e. selfshielding) has been proposed as a mass-independent mechanism for producing these isotopically distinct reservoirs. Self-shielding models predict the composition for the CO gas reservoir to be O-16-rich, and that the accreting primordial dust was in isotopic equilibrium with the gaseous reservoir [1, 2]. Self-shielding also predicts that cometary water, presumed to represent the O-17, O-18-rich reservoir, should be enriched in O-17 and O-18, with compositions of 200 -1000per mille, and that the interaction with this...

  8. Microstructural Constraints on the Formation History of Hibonite in Refractory Inclusions

    Han, J.; Koop, L.; Keller, L. P.; Davis, A. M.
    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...

  9. The Beryllium-10 Abundance in an Unusual Hibonite-Perovskite Refractory Inclusion from Allende: Implications for the Origin of Be-10

    Keller, L. P.; Liu, M-C.
    Beryllium-10 (decays to B-10, t1/2 = t(sub 1/2) = 1.3 Myr) 1.3 Myr) is a radionuclide that exclusively requires a is a radionuclide that exclusively requires a spallation origin. Therefore, one could obtain important insights into the irradiation environment in the solar nebula by understanding the distribution and abundance of this radionuclide in meteoritic inclusions. Most previous data are derived from B isotopic analysis of coarse-grained CV3 Ca-Al-rich Inclusions (CAIs) that have AL-26.Al-27 Al close to the canonical level of 5 x 10 (exp -5) and inferred Be-10/Be-9 ratios between 4 x 10(exp -4) and 1 x 10 (exp -2=3)...

  10. Spectral Characterization of Analog Samples in Anticipation of OSIRIS-REx's Arrival at Bennu

    Hamilton, V. E.; Lim, L. F.; Cloutis, E. A.; Schrader, D. L.; Bowles, N. E.; Keller, L. P.; Clark, B. E.; Connolly, H. C., Jr.; McCoy, T. J.; Lauretta, D. S.; Donaldson Hanna, K. L.
    NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission successfully launched on September 8th, 2016. During its rendezvous with near-Earth asteroid (101955) Bennu beginning in 2018, OSIRIS-REx will characterize the asteroid's physical, mineralogical, and chemical properties in an effort to globally map the properties of Bennu, a primitive carbonaceous asteroid, and choose a sampling location]. In preparation for these observations, analog samples were spectrally characterized across visible, near- and thermal-infrared wavelengths and were used in initial tests on mineral-phase-detection and abundance-determination software algorithms.

  11. The Abundance and Isotopic Signature of Chlorine in UrKREEP: Implications for the Early Degassing of the Moon

    Kanee, S.; Treiman. A. H.; Boyce, J. W.; Barnes, J. J.; Bricker, H.; McCubbin, F. M.
    Initally, the elevated delta-37 Cl values of lunar materials were attributed to volcanic degassing[1]. However, chlorine isotope ratios of apatite in lunarmare basalts appear to reflect mixing between two reservoirs.One component, with elevated delta-37 Cl is greater than or equal to + (25%) ([2] may represent the urKREEP--the final product of the crystallization of the lunar magma ocean. The second component, with delta-37 Cl is approximately (0%), is inferred to represent either a mare basalt reservoir or meteoritic materials. The idea that high delta-37 Cl is related to urKREEP suggest a global enrichment that occurred earlier in the lunar history...

  12. Toward a Safety Risk-Based Classification of Unmanned Aircraft

    Torres-Pomalas, Wilfredo
    The National Airspace System (NAS) is the large and complex network of airports, airways, and air traffic control facilities that support commercial, private, and military use of the national airspace. The NAS was created and has evolved to serve primarily manned aircraft operations. However, the ongoing development of unmanned aircraft (UA) technology has created the potential for significant economic benefits, and there is growing interest and demand for greater access of UA to the NAS. The lack of a comprehensive and efficient UA regulatory framework is severely constraining the number and kinds of UA operations that can be performed. The...

  13. Data Sharing in Astrobiology: the Astrobiology Habitable Environments Database (AHED)

    Pires, A.; Fonda, M.; Bristow, T.; Keller, R. M.; Blake, D.; Stone, N.; Downs, R. T.; Lafuente, B.
    Astrobiology is a multidisciplinary area of scientific research focused on studying the origins of life on Earth and the conditions under which life might have emerged elsewhere in the universe. NASA uses the results of Astrobiology research to help define targets for future missions that are searching for life elsewhere in the universe. The understanding of complex questions in Astrobiology requires integration and analysis of data spanning a range of disciplines including biology, chemistry, geology, astronomy and planetary science. However, the lack of a centralized repository makes it difficult for Astrobiology teams to share data and benefit from resultant synergies....

  14. Planetary Exploration of Lava Tubes with Lidar at Craters of the Moon, Idaho

    Hughes, S. S.; Lim, D. S. S.; Nawotniak, S. E. Kobs; Heldmann, J. L.; Whelley, P. L.; Garry, W. B.
    We completed a lidar survey of lava tubes in Idaho as an analog to the exploration of pits on the Moon and Mars. Pits are exploration targets for future missions because they provide both lucrative science and possible shelter. Exploration at these sites will require innovative engineering to access the interiors. We present findings that demonstrate the scientific and operational potential of lidar within such challenging environments, and discuss our results for Indian Tunnel, the largest tube we surveyed (Fig. 1).

  15. Effect of Tube-Based X-Ray Microtomography Imaging on the Amino Acid and Amine Content of the Murchison CM2 Chondrite

    Glavin, D. P.; Hill, M.; Ebel, D. S.; Friedrich, J. M.; Towbin, W. H.; Aponte, J. C.; Dworkin, J. P.; Elsila, J. E.; McLain, H. L.
    X-ray and synchrotron X-ray micro-computed tomography (micro-CT) are increasingly being used for three dimensional reconnaissance imaging of chondrites and returned extraterrestrial material prior to detailed chemical and mineralogical analyses. Although micro-CT imaging is generally considered to be a non-destructive technique since silicate and metallic minerals in chondrites are not affected by X-ray exposures at the intensities and wavelengths typically used, there are concerns that the use of micro-CT could be detrimental to the organics in carbonaceous chondrites. We recently conducted a synchrotron micro-CT experiment on a powdered sample of the Murchison CM2 carbonaceous chondrite exposed to a monochromatic high energy...

  16. On Measurements of the Tide at Churchill, Hudson Bay

    Ray, Richard D.
    Since the late 1990s the semi-diurnal tide at Churchill, on the western shore of Hudson Bay, has been decreasing in amplitude, with M(sub 2) amplitudes falling from approximately 154 cm in 1998 to 146 cm in 2012 and 142 cm in 2014. There has been a corresponding small increase in phase lag. Mean low water, decreasing throughout most of the twentieth century, has levelled off. Although the tidal changes could reflect merely a malfunctioning tide gauge, the fact that there are no other measurements in the region and the possibility that the tide is revealing important environmental changes calls for...

  17. Evidence for a Dynamic Nanodust Cloud Enveloping the Moon

    Glenar, D. A.; Cook, A. M.; Shirley, M.; Stubbs, T. J.; Wooden, D. H.; Colaprete, A.
    The exospheres that surround airless bodies such as the Moon are tenuous, atmosphere-like layers whose constituent particles rarely collide with one another. Some particles contained within such exospheres are the product of direct interactions between airless bodies and the space environment, and offer insights into space weathering processes. NASAs Lunar Atmosphere and Dust Environment Explorer (LADEE) mission studied the Moons exospheric constituents in situ and detected a permanent dust exosphere1 of particles with radii as small as 300 nm. Here we present evidence from LADEE spectral data for an additional fluctuating nanodust exosphere at the Moon containing a population of...

  18. On Tidal Inference in the Diurnal Band

    Ray, R. D.
    Standard methods of tidal inference should be revised to account for a known resonance that occurs mostly within the K(sub 1) tidal group in the diurnal band. The resonance arises from a free rotational mode of Earth caused by the fluid core. In a set of 110 bottom-pressure tide stations, the amplitude of the P(sub 1) tidal constituent is shown to be suppressed relative to K(sub 1), which is in good agreement with the resonance theory. Standard formulas for the K(sub 1) nodal modulation remain essentially unaffected. Two examples are given of applications of the refined inference methodology: one with...

  19. Van Allen Probes, THEMIS, GOES, and Cluster Observations of EMIC Waves, ULF Pulsations, and an Electron Flux Dropout

    Baker, D. N.; Singer, H. J.; Spence, H.; Sigsbee, K.; Smith, C. W.; Green, J. C.; Blake, J. B.; Reeves, G.; Santolík, O.; Kletzing, C. A.; Carr, C.; Macdowall, R.
    We examined an electron flux dropout during the 12-14 November 2012 geomagnetic storm using observations from seven spacecraft: the two Van Allen Probes, Time History of Events and Macroscale Interactions during Substorms (THEMIS)-A (P5), Cluster 2, and Geostationary Operational Environmental Satellites (GOES) 13, 14, and 15. The electron fluxes for energies greater than 2.0 MeV observed by GOES 13, 14, and 15 at geosynchronous orbit and by the Van Allen Probes remained at or near instrumental background levels for more than 24 h from 12 to 14 November. For energies of 0.8 MeV, the GOES satellites observed two shorter intervals...

  20. Mercury's Seasonal Sodium Exosphere: MESSENGER Orbital Observations

    McClintock, William E.; Killen, Rosemary M.; Sarantos, Menelaos; Merkel, Aimee W.; Burger, Matthew H.; Cassidy, Timothy A.; Vervack, Ronald J., Jr.
    The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Ultraviolet and Visible Spectrometer (UVVS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft now orbiting Mercury provides the first close-up look at the planet's sodium exosphere. UVVS has observed the exosphere from orbit almost daily for over 10 Mercury years. In this paper we describe and analyze a subset of these data: altitude profiles taken above the low-latitude dayside and south pole. The observations show spatial and temporal variation but there is little or no year-to-year variation; we do not see the episodic variability reported by ground-based observers. We...

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