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  • Life and Medical Sciences  (2,848)
  • ASTROPHYSICS  (2,809)
  • Inorganic Chemistry  (2,258)
  • Lunar and Planetary Science and Exploration  (2,215)
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  • 1
    Publication Date: 2019-08-14
    Description: Establishing the abundance and physical properties of regolith and boulders on asteroids is crucial for understanding the formation and degradation mechanisms at work on their surfaces. Using images and thermal data from NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft, we show that asteroid (101955) Bennu's surface is globally rough, dense with boulders, and low in albedo. The number of boulders is surprising given Bennu's moderate thermal inertia, suggesting that simple models linking thermal inertia to particle size do not adequately capture the complexity relating these properties. At the same time, we find evidence for a wide range of particle sizes with distinct albedo characteristics. Our findings imply that ages of Bennu's surface particles span from the disruption of the asteroid's parent body (boulders) to recent in situ production (micrometre-scale particles).
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN67770 , Nature Astronomy (e-ISSN 2397-3366); 3; 341–351
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  • 2
    Publication Date: 2019-08-26
    Description: OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This article describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at level 100 A/2 and less than 180 ng/cm(exp 2) of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication among scientists, engineers, managers, and technicians.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN50790 , Space Science Review (ISSN 0038-6308) (e-ISSN 1572-9672); 214; 1; 19
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  • 3
    Publication Date: 2019-08-13
    Description: OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This manuscript describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at Level 100 A/2 and less than 180 nanograms per square centimeter of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication between scientists, engineers, managers, and technicians.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN41800 , International Conference on the Origin of Life; Jul 16, 2018 - Jul 21, 2018; San Diego, CA; United States
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  • 4
    Publication Date: 2019-07-13
    Description: The Mars Science Laboratory (MSL) mission is focused on assessing the past or present habitability of Mars, through interrogation of environment and environmental records at the Curiosity rover field site in Gale crater. The MSL team has two methods available to collect, process and deliver samples to onboard analytical laboratories, the Chemistry and Mineralogy instrument (CheMin) and the Sample Analysis at Mars (SAM) instrument suite. One approach obtains samples by drilling into a rock, the other uses a scoop to collect loose regolith fines. Scooping was planned to be first method performed on Mars because materials could be readily scooped multiple times and used to remove any remaining, minute terrestrial contaminants from the sample processing system, the Collection and Handling for In-Situ Martian Rock Analysis (CHIMRA). Because of this cleaning effort, the ideal first material to be scooped would consist of fine to very fine sand, like the interior of the Serpent Dune studied by the Mars Exploration Rover (MER) Spirit team in 2004 [1]. The MSL team selected a linear eolian deposit in the lee of a group of cobbles they named Rocknest (Fig. 1) as likely to be similar to Serpent Dune. Following the definitions in Chapter 13 of Bagnold [2], the deposit is termed a sand shadow. The scooping campaign occurred over approximately 6 weeks in October and November 2012. To support these activities, the Mars Hand Lens Imager (MAHLI) acquired images for engineering support/assessment and scientific inquiry.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-27937 , Lunar and Planetary Science Conference; Mar 18, 2013 - Mar 22, 2013; The Woodlands, TX; United States
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  • 5
    Publication Date: 2020-03-26
    Description: Mariner 10 provided our first closeup reconnaissance of Mercury during its three flybys in 1974 and 1975. MESSENGERs 20112015 orbital investigation enabled numerous discoveries, several of which led to substantial or complete changes in our fundamental understanding of the planet. Among these were the unanticipated, widespread presence of volatile elements (e.g., Na, K, S); a surface with extremely low Fe abundance whose darkening agent is likely C; a previously unknown landformhollows that may form by volatile sublimation from within rocks exposed to the harsh conditions on the surface; a history of expansive effusive and explosive volcanism; substantial radial contraction of the planet from interior cooling; offset of the dipole moment of the internal magnetic field northward from the geographic equator by ~20% of the planets radius; crustal magnetization, attributed at least in part to an ancient field; unexpected seasonal variability and relationships among exospheric species and processes; and the presence in permanently shadowed polar terrain of water ice and other volatile materials, likely to include complex organic compounds. Mercurys highly chemically reduced and unexpectedly volatile-rich composition is unique among the terrestrial planets and was not predicted by earlier hypotheses for the planets origin. As an end-member of terrestrial planet formation, Mercury holds unique clues about the original distribution of elements in the earliest stages of the Solar System and how planets (and exoplanets) form and evolve in close proximity to their host stars. The BepiColombo mission promises to expand our knowledge of this planet and to shed light on some of the mysteries revealed by the MESSENGER mission. However, several fundamental science questions raised by MESSENGERs pioneering exploration of Mercury can only be answered with in situ measurements from the planets surface.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-E-DAA-TN77065 , Lunar and Planetary Science Conference (LPSC); Mar 16, 2020 - Mar 20, 2020; The Woodlands, TX; United States
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  • 6
    Publication Date: 2020-03-26
    Description: The data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have revealed several surprising characteristics about the surface of Mercury, leading to its classification as a geochemical endmember among the terrestrial planets. Some of these features include elevated abundances of up to 3 wt% S, C enrichment as high as 4 wt% over the local mean in low reflectance materials (LRM), Na up to 5 wt% at high northern latitudes, and Fe abundances typically lower than 2 wt% [e.g., 14]. The S and Fe concentrations have been used to infer that Mercurys igneous history evolved under highly reduced oxygen fugacity conditions between 2.6 and 7.3 log10 units below the iron-wstite buffer [e.g., 5], which is more reducing than any other terrestrial planet in the solar system [e.g., 6]. This highly reduced nature has important consequences for the differentiation and thermal/magmatic evolution of Mercury. While the immense amount of data collected by MESSENGER revealed Mercury as a geochemical endmember, this new knowledge gained raised additional questions that necessitate continued exploration of the planet. Fortunately, BepiColombo launched in October of 2018, and this joint ESA/JAXA dual-orbiter spacecraft is the most ambitious effort yet attempted to explore Mercury [e.g., 7]. Looking beyond BepiColombo, there are major aspects of Mercurys geochemical character and evolution for which significant knowledge gaps can be dramatically improved with data acquired from the planets surface via in situ landed science.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-E-DAA-TN77061 , Lunar and Planetary Science Conference; Mar 16, 2020 - Mar 20, 2020; The Woodlands, TX; United States
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  • 7
    Publication Date: 2019-07-13
    Description: MAHLI (Mars Hand Lens Imager) is a 2-megapixel focusable macro lens color camera on the turret on Curiosity's robotic arm. The investigation centers on stratigraphy, grain-scale texture, structure, mineralogy, and morphology of geologic materials at Curiosity's Gale robotic field site. MAHLI acquires focused images at working distances of 2.1 cm to infinity; for reference, at 2.1 cm the scale is 14 microns/pixel; at 6.9 cm it is 31 microns/pixel, like the Spirit and Opportunity Microscopic Imager (MI) cameras.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science Conference (LPSC 2013); Mar 18, 2013 - Mar 22, 2013; The Woodlands, TX; United States
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  • 8
    Publication Date: 2018-06-11
    Description: The Miniature Thermal Emission Spectrometer (Mini-TES) on Spirit has studied the mineralogy and thermophysical properties at Gusev crater. Undisturbed soil spectra show evidence for minor carbonates and bound water. Rocks are olivinerich basalts with varying degrees of dust and other coatings. Dark-toned soils observed on disturbed surfaces may be derived from rocks and have derived mineralogy (+/-5 to 10%) of 45% pyroxene (20% Ca-rich pyroxene and 25% pigeonite), 40% sodic to intermediate plagioclase, and 15% olivine (forsterite 45% +/-5 to 10). Two spectrally distinct coatings are observed on rocks, a possible indicator of the interaction of water, rock, and airfall dust. Diurnal temperature data indicate particle sizes from 40 to 80 microm in hollows to approximately 0.5 to 3 mm in soils.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Science (ISSN 0036-8075); Volume 305; 5685; 837-42
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  • 9
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this study, the intracellular concentrations of six elements (mmole/kg dry weight) were directly measured in the muscle fibers of pectoralis major muscles of eight week old, genetically dystrophic and normal chickens by the X-ray microanalysis technique. The extent of muscle degeneration was evaluated by morphometric measurements of muscle fiber diameter and other histological changes. A significant increase in the concentration of intracellular sodium and chlorine was evident in dystrophic muscles. The concentration of intracellular sodium was 127.0 ± 35.0 in the muscle fibers of dystrophic chicks compared to 65.7 ± 16.5 in normal controls. The concentration of chlorine was 90.5 ± 27.5 and 54.1 ± 5.5 in the muscle fibers of dystrophic and normal chicks respectively. The intracellular concentrations of potassium, magnesium, phosphorous, and sulfur remained unchanged in the dystrophic condition. Morphometric studies revealed that the dystrophic pectoralis muscles contain fewer but thicker fibers per unit area compared to normal pectoralis muscles. The importance of these findings are discussed in relation to the results of earlier investigations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0197-8462
    Keywords: millimeter-wave radiation ; BHK-21/C13 cells in monolayer culture ; scanning electron microscopy ; transmission electron microscopy ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Both thermal and athermal effects of millimeter-wave radiation on BHK-21/C13 cells were sought using scanning and transmission electron microscopy in conjunction with an in vitro technique that allows direct exposure of monolayer cultures to high average power densities. Culture dishes were irradiated by placing them on the open end of an E- or U-band wave guide. This technique exposes different regions of the cell monolayer lying along the longer axis of the wave guide aperture to varying power densities ranging from zero at each edge to twice the average power density at the center.Cell ultrastructure was unaffected by microwave radiation for 1 hour (41.8 or 74.0 GHz, average power densitites = 320 or 450 mW/cm2, respectively) with or without cooling by rapid recirculation of the culture medium. Temperature in recirculated cultures was held at 37.2 °C, and that in noncooled cultures never exceeded 42 °C during irradiation at either power density. In contrast, cell morphology was affected by microwave exposure whenever irradiation conditions were altered so that the temperature of the monolayer reached or exceeded 44.5 °C. Ultrastructural alterations included breakage of cell processes, progressive detachment of cells from the substrate, increased clumping of heterochromatin in the nuclei, and the appearance of large empty vesicles in the cytoplasm. Such morphological changes resulted from either application of higher average power densities or irradiation at the power densities described above at a higher ambient temperature (〉38.5°C).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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