Recursos de colección

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 81 - 100 de 320.544

  1. Jezero Crater, Mars, as a Compelling Site for Future In Situ Exploration

    Gupta, S.; Goudge, T. A.; Brown, A. J.; Ehlmann, B. L.; Head, J. W.; Mangold, N.; Fassett, C. I.; Mustard, J. F.; Milliken, R. E.
    Jezero is a approximately 45 km diameter impact crater located in the Nili Fossae region of Mars. Jezero is an outstanding site to address key questions of ancient Mars climate, habitability, and volcanic history because: (a) It hosted an open-basin lake during the era of valley network formation [1,2], which ceased at approximately the Noachian-Hesperian boundary [3]. (b) It contains two delta deposits [1,4] with Fe/Mg-smectite and Mg-carbonate sediment [4-7] (the only exposure of lacus-trine shoreline carbonates seen so far on Mars). (c) The depositional environment and mineral assemblage of the delta are promising for the concentration and preservation of...

  2. Stratigraphy and Evolution of Delta Channel Deposits, Jezero Crater, Mars

    Cardenas, B. T.; Hughes, C. M.; Fassett, C. I.; Goudge, T. A.; Mohrig, D.
    The Jezero impact crater hosted an open-basin lake that was active during the valley network forming era on early Mars. This basin contains a well exposed delta deposit at the mouth of the western inlet valley. The fluvial stratigraphy of this deposit provides a record of the channels that built the delta over time. Here we describe observations of the stratigraphy of the channel deposits of the Jezero western delta to help reconstruct its evolution.

  3. Evolution of Circular Polarization Ratio (CPR) Profiles of Kilometer-scale Craters on the Lunar Maria

    King, I. R.; Watters, W. A.; Thomson, B. J.; Minton, D. A.; Fassett, C. I.
    When sufficiently large impact craters form on the Moon, rocks and unweathered materials are excavated from beneath the regolith and deposited into their blocky ejecta. This enhances the rockiness and roughness of the proximal ejecta surrounding fresh impact craters. The interior of fresh craters are typically also rough, due to blocks, breccia, and impact melt. Thus, both the interior and proximal ejecta of fresh craters are usually radar bright and have high circular polarization ratios (CPR). Beyond the proximal ejecta, radar-dark halos are observed around some fresh craters, suggesting that distal ejecta is finer-grained than background regolith. The radar signatures...

  4. Crater Morphometry and Crater Degradation on Mercury: Mercury Laser Altimeter (MLA) Measurements and Comparison to Stereo-DTM Derived Results

    Fassett, C. I.; Crowley, M. C.; Leight, C.; Dyar, M. D.
    Two types of measurements of Mercury's surface topography were obtained by the MESSENGER (MErcury Surface Space ENvironment, GEochemisty and Ranging) spacecraft: laser ranging data from Mercury Laser Altimeter (MLA) [1], and stereo imagery from the Mercury Dual Imaging System (MDIS) camera [e.g., 2, 3]. MLA data provide precise and accurate elevation meaurements, but with sparse spatial sampling except at the highest northern latitudes. Digital terrain models (DTMs) from MDIS have superior resolution but with less vertical accuracy, limited approximately to the pixel resolution of the original images (in the case of [3], 15-75 m). Last year [4], we reported topographic...

  5. The Potassium-Argon Laser Experiment (KArLE): Design Concepts

    Cohen, B. A.; Cho, Y.
    The absolute ages of geologic events are fundamental information for understanding the timing and duration of surface processes on planetary bodies. Absolute ages can place a planet's history in the context of the solar system evolution. For example, "when was Mars warm and wet?" is one of the key questions of planetary science. If Mars was warm and wet until 3.7 billion years ago, for instance, it suggests that Mars was still warm and wet when life appeared on Earth. Mars history has been discussed so far based on crater chronology, but the current constraints for Martian chronology models come...

  6. Shallow Lunar Seismic Activity and the Current Stress State of the Moon

    Johnson, C. L.; Weber, R. C.; Collins, G. C.; Watters, T. R.
    A vast, global network of more than 3200 lobate thrust fault scarps has been revealed in high resolution Lunar Reconnaissance Orbiter Camera (LROC) images. The fault scarps very young, less than 50 Ma, based on their small scale and crisp appearance, crosscutting relations with small-diameter impact craters, and rates of infilling of associated small, shallow graben and may be actively forming today. The population of young thrust fault scarps provides a window into the recent stress state of the Moon and offers insight into the origin of global lunar stresses. The distribution of orientations of the fault scarps is non-random,...

  7. Documenting Chemical Assimilation in a Basaltic Lava Flow

    Scheidt, S.; Needham, D. H.; Williams, D.; Bleacher, J. E.; Rogers, A. D.; Glotch, T.; Evans, C.; Whelley, P. L.; Young, K. E.
    Lava channels are features seen throughout the inner Solar System, including on Earth, the Moon, and Mars. Flow emplacement is therefore a crucial process in the shaping of planetary surfaces. Many studies have investigated the dynamics of lava flow emplacement, both on Earth and on the Moon [1,2,3] but none have focused on how the compositional and structural characteristics of the substrate over which a flow was emplaced influenced its final flow morphology. Within the length of one flow, it is common for flows to change in morphology, a quality linked to lava rheology (a function of multiple factors including...

  8. Unveiling the Mysteries of Mars with a Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM)

    Gaskin, J. A.; Doloboff, I. J.; Edmunson, J.
    Development of a miniaturized scanning electron microscope that will utilize the martian atmosphere to dissipate charge during analysis continues. This instrument is expected to be used on a future rover or lander to answer fundamental Mars science questions. To identify the most important questions, a survey was taken at the 47th Lunar and Planetary Science Conference (LPSC). From the gathered information initial topics were identified for a SEM on the martian surface. These priorities are identified and discussed below. Additionally, a concept of operations is provided with the goal of maximizing the science obtained with the minimum amount of communication...

  9. Clasp2 (Re-Flight Planning) Aiming at Establishing the Magnetic Field Diagnostic Technique by the UV Spectro-Polarimetry

    Kubo, Masahito; Tsuzuki, Toshihiro; Shinoda, Kazuya; Suematsu, Yoshiho; Hara, Hirohisa; Ishikawa, Shinnosuke; Kano, Ryohei; Kobayashi, K.; McKenzie, D.; Ishikawa, Ryoko; Noriyuki, Narukage; Rachmeler, L.; Taketen, Okamoto
    No abstract available

  10. Non-Targeted Effects and LET: Considerations for Earth and Space Research

    Sowa, Marianne B.
    It is evident from reports in the literature that there are many confounding factors that are capable of modulating radiation-induced non-targeted responses such as the bystander effect and the adaptive response. It has even been suggested that the observation of non-targeted responses may not be universally observable for differing radiation qualities. Dr. William Morgan made many contributions to the study of radiation induced non-targeted effects and it is indeed this area of research where we first began our collaboration more than a decade ago. In this presentation, I will discuss elements of this journey together with a particular emphasis on...

  11. What to Wear When You're Out There

    Aitchison, Lindsay
    No abstract available

  12. The Carnegie Hubble Program: The Distance and Structure of the SMC as Revealed by Mid-Infrared Observations of Cepheids

    Seibert, Mark; Monson, Andy; Scowcroft, Victoria; Rich, Jeff; Persson, S. E.; Madore, Barry F.; Freedman, Wendy L.; Rigby, Jane R.
    Using Spitzer observations of classical Cepheids we have measured the true average distance modulus of the Small Magellanic Cloud (SMC) to be18.96 +/- 0.01 stat +/- 0.03sys mag (corresponding to 62+/- 0.3kpc), which is 0.48 +/- 0.01 mag more distant than the LMC. This is in agreement with previous results from Cepheid observations, as well as with measurements from other indicators such as RR Lyrae stars and the tip of the red giant branch. Utilizing the properties of the mid-infrared Leavitt Law we measured precise distances to individual Cepheids in the SMC, and have confirmed that the galaxy is tilted...

  13. NuSTAR and XMM-Newton Observations of the Hard X- Ray Spectrum of Centaurus A

    Rivers, E.; Zhang, W.; Furst, F.; Brightman, M.; Muller, C.; Madsen, K. K.; Beuchert, T.; Balokovic, M.; Arevalo, P.; Lanz, L.
    We present simultaneous XMM-Newton and Nuclear Spectroscopic Telescope Array (NuSTAR) observations spanning 3-78 keV of the nearest radio galaxy, Centaurus A (Cen A). The accretion geometry around the central engine in Cen A is still debated, and we investigate possible configurations using detailed X-ray spectral modeling. NuSTAR imaged the central region of Cen A with subarcminute resolution at X-ray energies above 10 keV for the first time, but found no evidence for an extended source or other off-nuclear point sources. The XMM-Newton and NuSTAR spectra agree well and can be described with an absorbed power law with a photon index...

  14. Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013

    Becerra Gonzalez, J.; Christensen, F. E.; Blandford, R. D.; Furniss, A.; Barret, D.; Stern, D.; Boggs, S. E.; Chiang, J.; Zhang, W. W.; Madejski, G.; Paneque, D.; Perkins, J.; Smith, A. W.; Alexander, D. M.; Ajello, M.; Balokovic, M.
    We present coordinated multiwavelength observations of the bright, nearby BL Lacertae object Markarian 421 (Mrk 421) taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very high energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79 kiloelectronvolt range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep Gamma approximating 3 power law, with no evidence for an exponential cutoff or additional hard components up to 80 kiloelectronvolts. For the first time, we observed both the...

  15. A Space-based, High-resolution View of Notable Changes in Urban Nox Pollution Around the World (2005 - 2014)

    Duncan, Bryan N.; Streets, David G.; Thompson, Anne M.; Yoshida, Yasuko; Lu, Zifeng; Lamsal, Lok N.; Hurwitz, Margaret M.; Pickering, Kenneth E.
    Nitrogen oxides (NOxNO+NO2) are produced during combustion processes and, thus may serve as a proxy for fossil fuel-based energy usage and committed greenhouse gases and other pollutants. We use high-resolution nitrogen dioxide (NO2) data from the Ozone Monitoring Instrument (OMI) to analyze changes in urban NO2 levels around the world from 2005 to 2014, finding complex heterogeneity in the changes. We discuss several potential factors that seem to determine these NOx changes. First, environmental regulations resulted in large decreases. The only large increases in the United States may be associated with three areas of intensive energy activity. Second, elevated NO2...

  16. Documenting Surface and Sub-surface Volatiles While Drilling in Frozen Lunar Simulant

    Roush, T. L.; Colaprete, A.; White, B.; McMurray, R.; Bielawski, R.; Kleinhenz, J.; Smith, J.; Fritzler, E.; Zacny, K.; Benton, J.; Paulsen, G.; Cook, A. M.; Forgione, J.
    NASA's Resource Prospector (RP) mission is intended to characterize the three-dimensional nature of volatiles in lunar polar regions and permanently shadowed regions. RP is slated to carry two instruments for prospecting purposes. These include the Neutron Spectrometer System (NSS) and Near-Infrared Volatile Spectrometer System (NIRVSS). A Honybee Robotics drill (HRD) is intended to sample to depths of 1 m, and deliver a sample to a crucible that is processed by the Oxygen Volatile Extraction Node (OVEN) where the soil is heated and evolved gas is delivered to the gas chromatograph / mass spectrometer of the Lunar Advanced Volatile Analysis system...

  17. Resource Prospector: An Update on the Lunar Volatiles Prospecting and ISRU Demonstration Mission

    Trimble, J.; Bluethmann, B.; Chavers, G.; Quinn, J.; Colaprete, A.; Elphic, R.; Andrews, D.
    Over the last two decades a wealth of new observations of the moon have demonstrated a lunar water system dramatically more complex and rich than was deduced following the Apollo era. Lunar water, and other volatiles, have the potential to be a valuable or enabling resource for future exploration. The NASA Human Exploration and Operations Mission Directorate (HEOMD) have selected a lunar volatiles prospecting mission for a concept study and potential flight in CY2021. The mission includes a rover-borne payload that (1) can locate surface and near-subsurface volatiles, (2) excavate and analyze samples of the volatile- bearing regolith, and (3)...

  18. Lessons from Astrobiological Planetary Analogue Exploration in Iceland: Biomarker Assay Performance and Downselection

    Cullen, T.; Stevens,; Duca, Z.; Stockton, A.; Murukesan, G.; Rennie, V.; Cable, M. L.; Cullen, D.; Yin, C.; Cantrell, T.; Schwieterman, E.; McCaig, H.; Tan, G.; Kirby, J.; Gentry, D. M.; Geppert, W.; Jacobsen, M.; Chaudry, N.; Amador, E. S.
    Understanding the sensitivity of biomarker assays to the local physicochemical environment, and the underlying spatial distribution of the target biomarkers in 'homogeneous' environments, can increase mission science return. We have conducted four expeditions to Icelandic Mars analogue sites in which an increasingly refined battery of physicochemical measurements and biomarker assays were performed, staggered with scouting of further sites. Completed expeditions took place in 2012 (location scouting and field assay use testing), 2013 (sampling of two major sites with three assays and observational physicochemical measurements), 2015 (repeat sampling of prior sites and one new site, scouting of new sites, three assays...

  19. Multi-View Shape-from-Shading for Planetary Images with Challenging Illumination

    Beyer, Ross; Alexandrov, Oleg
    We describe our approach for using shape-from-shading to create very high quality terrains on the Moon and other planets using images with various illumination conditions.

  20. Enabling a Science Support Structure for NASAs Global Hawk UASs

    Sullivan, Donald V.
    In this paper we describe the information technologies developed by NASA for the Winter/Spring 2013/2014, and Fall 2014, NASA Earth Venture Campaigns, Hurricane and Severe Storm Sentinel (HS3) and Airborne Tropical TRopopause EXperiment (ATTREX). These campaigns utilized Global Hawk UAS vehicles equipped at the NASA Armstrong (previously Dryden) Flight Research Facility (AFRC), Edwards Air Force Base, California, and operated from there, the NASA Wallops Flight Facility (WFF), Virginia, and Anderson Air Force Base (AAFB), Guam. Part of this enabling infrastructure utilized a layer 2 encrypted terrestrial Virtual Local Area Network (VLAN) that, at times, spanned greater than ten thousand miles...

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