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  • Analytical Chemistry and Spectroscopy  (4,318)
  • Inorganic Chemistry  (3,506)
  • LUNAR AND PLANETARY EXPLORATION  (3,213)
  • 1980-1984  (11,037)
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  • 101
    Publication Date: 2011-08-19
    Description: In the present extension of Cess and Caldwell's (1979) seasonal climate model to the upper troposphere of Saturn, the ring-modulated latitudinal dependence of the insolation, the ring thermal emission, the oblateness and orbital eccentricity of the planet, and the latitudinal variation of the internal heat flux, are taken into account. While these calculations agree with the temperature-latitude profiles retrieved from Voyager IRIS measurements above 0.2-bar pressure level atmospheric strata, the model fails to predict the retrieved temperature-latitude profiles below the 0.3-bar level. This discrepancy may be due to the existence of clouds at these levels.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 60; 274-288
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  • 102
    Publication Date: 2011-08-19
    Description: Although lightning has not yet been observed in Titan's atmosphere, the presence of condensable vapors and the deposition of a significant amount of solar energy at the surface suggest the possibility of lightning activity. Based on an understanding of the relationship of lightning activity to the amount of convective energy available on Titan, a lightning energy dissipation rate of 4 x 10 to the -6th W/sq m can be expected. This value is much lower than that for earth or Jupiter, and is a result of both the reduced solar flux at Titan and the absorption of sunlight by the aerosols that lie above the convective layer. For this dissipation rate, the amount of HCN and C2N2 produced by lightning should be greater than that by solar UV, but could be less than that produced by electron precipitation and galactic cosmic rays. Equilibrium calculations indicate that large mole fractions of elemental solid phase carbon will also be produced. Using a simplified model of aerosol formation, coagulation, and settling, it is estimated that a lightning-produced aerosol could have a typical optical depth of 0.01, with values as high as 0.1. The accumulation of soot over geological time might reach a meter or more in depth.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 60; 260-273
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  • 103
    Publication Date: 2011-08-19
    Description: The present absolute measurements of Titan, Uranus and Neptune geometric albedo spectra in the 3500-10,500 A range have a resolution of about 7 A, together with high SNR, in virtue of the exceptional effeciency of the spectrograph and Reticon detector employed. The high precision and spectral resolution of the data, which are in excellent agreement with the Uranus albedo measurements of Lockwood et al. (1983), make possible quantitative measurements of the effects of Raman scattering by H2 in the Uranus and Neptune atmospheres.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 60; 221-235
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  • 104
    Publication Date: 2011-08-19
    Description: A radically different model of Saturn's ionosphere is proposed in which water plays a major role as a minor constituent present by downward diffusion from an external source. The model ionosphere is a classical F2 type layer resulting from the photodissociative production of H(+) from H2 and rapid chemical loss by a series of charge exchange reactions with water. A planet-wide influx of about 4 x 10 to the 7th molecules/sq cm/s of water from the rings is consistent with the observed ionospheric electron densities. An enhanced influx of water occurs at latitudes (-38, +44 deg) connected magnetically at the inner edge of Saturn's B ring, where an electromagnetic erosion process takes place. The present-day influx at these latitudes may be as large as 2 x 10 to the 9th molecules/sq cm/s.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 312; 136-138
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  • 105
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    Publication Date: 2011-08-19
    Description: The ring systems of Jupiter, Saturn and Uranus have been studied particularly since the Voyager flights, in order to obtain more information on the rings' origin and structure. These ring systems all have satellites but the structure and number of satellites are different. Jupiter, with its two satellites, has a ring that is roughly 6000 km wide while Uranus has nine ringlets, most of which are no wider than tens of kilometers and which are separated by empty space. The three planetary ring systems also show distinctions in composition; for example, the rings of Saturn are thought to be icy while Jupiter's consist mostly of rocky material. The effect that countless particles, which make up each ring and interact with each other through collisions and gravitational attractions, have on the system's energy and angular momentum has been discussed. Spiral density waves and spiral bending waves, are explained by the resonance theory. Further study is needed in this area since the resonance theory does not account for all observed ring structures.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sky and Telescope (ISSN 0037-6604); 68; 511-515
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  • 106
    Publication Date: 2011-08-19
    Description: A three-dimensional, spherical, primitive equation eigenvalue model is used to investigate the baroclinic stability properties of the wind and temperature fields in the Venus atmosphere as measured by Pioneer Venus. It is found that baroclinic instability occurs in the region of the middle cloud deck. The most unstable modes have growth times less than eight days and are vertically confined to the region near the middle cloud layer. The most unstable baroclinic mode at zonal wavenumber 2 has characteristics similar to those observed for the high latitude rotating dipole thermal feature. Certain planetary scale baroclinic modes can penetrate to relatively high altitudes under the right circumstances, and may therefore explain some of the wave features observed between 60 and 90 km. For example, thermal oscillations with periods between four and seven days occurring at middle latitudes have characteristics which appear to be consistent with computed properties of planetary scale baroclinic modes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 41; 2310-233
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  • 107
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    Publication Date: 2011-08-19
    Description: The first two-dimensional images of the source region of Io's neutral sodium cloud have been acquired by ground-based observation. Observed asymmetries in its spatial brightness distribution provide new evidence that the cloud is supplied by sodium that is ejected nonisotropically from Io or its atmosphere. Complementary, high-time-resolution, calibrated image sequences that give the first comprehensive picture of the variations of the fainter regions of the cloud extending more than 100,000 kilometers from Io were also obtained. These data demonstrate that the cloud exhibits a persistent systematic behavior coupled with Io's orbital position, a distinct 'east-west orbital asymmetry', a variety of spatial morphologies, and true temporal changes. The geometric stability of the sodium source is also indicated. Isolation of the cloud's temporal changes constitutes an important milestone toward its utilization as a long-term probe of Io and the inner Jovian magnetosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 226; 512-516
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  • 108
    Publication Date: 2011-08-19
    Description: The missions of the Pioneer multiprobe and orbiter spacecraft to Venus are surveyed and illustrated with drawings, photographs, maps, and diagrams. The general characteristics of Venus and the pre-Pioneer missions are reviewed; the developmental history of the Pioneer project is traced; the spacecraft and their orbits and deployment are described; and the scientific findings on the planet surface, atmosphere, and ionosphere are summarized. The experiments planned for the extended mission of the orbiter (through reentry in 1992) are briefly characterized, includidng solar-wind-interaction studies, comet detection, ionosphere and aeronomy investigations, global lightning survey, optical observations, gamma-ray-burst detection, radar mapping, gravity measurements, and observations of Halley's Comet during February, 1986.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0007-084X); 37; 453-467
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  • 109
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    Publication Date: 2011-08-18
    Description: It is pointed out that volcanoes are morphological expressions of magma composition, eruption processes, and regional tectonics. Thus, the lack of unambiguous silicic volcanoes and pyroclastic flows on Mars implies that compared to earth, its crust is deficient in volatiles and/or the planet lacks a thick granitic crust. Such deductions are examples of comparative planetology, in which knowledge of landforms and processes on one planet are utilized to interpret features and histories on others. In the present study calderas are considered in a comparative planetology context to provide perspective for students who investigate only terrestrial calderas and to search for broadscale relationships between calderas and planetary characteristics. Attention is given to terrestrial calderas, lunar calderas, Martian calderas, calderas on Jupiter's satellite Io, and calderas on Venus. A planetary definition of calderas is proposed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 8391-840
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  • 110
    Publication Date: 2011-08-18
    Description: Magnetic field observations obtained by the Pioneer 11 vector helium magnetometer are compared with the Z(sub 3) model magnetic field. These Pioneer 11 observations, obtained at close-in radial distances, constitute an important and independent test of the Z(sub 3) zonal harmonic model, which was derived from Voyager 1 and Voyager 2 fluxgate magnetometer observations. Differences between the Pioneer 11 magnetometer and the Z(sub 3) model field are found to be small (approximately 1 percent) and quantitatively consistent with the expected instrumental accuracy. A detailed examination of these differences in spacecraft payload coordinates shows that they are uniquely associated with the instrument frame of reference and operation. A much improved fit to the Pioneer 11 observations is obtained by rotation of the instrument coordinate system about the spacecraft spin axis by 1.4 degree. With this adjustment, possibly associated with an instrumental phase lag or roll attitude error, the Pioneer 11 vector helium magnetometer observations are fully consistent with the Voyager Z(sub 3) model.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 7541-754
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  • 111
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    Publication Date: 2011-08-18
    Description: Determinations by spacecraft of the low-frequency radio spectra and radiation beam geometry of the magnetospheres of earth, Jupiter, and Saturn now permit a reliable assessment of the overall efficiency of the solar wind in stimulating intense, nonthermal radio bursts from these magnetospheres. It is found that earlier estimates of how magnetospheric radio output scales with the solar wind energy input must be greatly revised, with the result that, while the efficiency is much lower than previously thought, it is remarkably uniform from planet to planet. A 'radimetric Bode's law' is formulated from which a planet's magnetic moment can be estimated from its radio emission output. This law is applied to estimate the low-frequency radio power likely to be measured for Uranus by Voyager 2. It is shown how measurements of Uranus's radio flux can be used to estimate the planetary magnetic moment and solar wind stand-off distance before the in situ measurements.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 310; 755-757
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  • 112
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    Publication Date: 2011-08-18
    Description: This paper examines several mechanisms for generation of field-aligned currents in the magnetospheres of earth and Jupiter. Implications for planetary radio emission in relation to field-aligned current systems are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 113
    Publication Date: 2011-08-18
    Description: The asteroid 133 Cyrene was observed photometrically on 17 nights during oppositions in 1979 and 1980. The synodic period of rotation was found to be 12.708 + or - 0.001 h with an amplitude of 0.30 m during both oppositions. At large phase angles, the phase relation is quite ordinary (0.025 mag/degree); however, the low phase angle observations reveal a dramatic opposition brightening, about 0.2 mag/degree near zero phase angle. The absolute magnitude, V(1,0), extrapolated with the above linear phase coefficient, is 8.40. The following color indices were also measured: B-V = 0.90, U-B = 0.51.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 58; 377-382
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  • 114
    Publication Date: 2011-08-18
    Description: The helium abundance in the atmosphere of Saturn is obtained from Voyager measurements by two methods. The first method combines infrared spectra and vertical profiles derived from radio occultation measurements and yields a hydrogen mole fraction of q = 0.963 + or - 0.024 corresponding to a helium mass fraction of Y = 0.06 + or - 0.05. The estimated errors are primarily due to uncertainties in the radio occultation profile and in the abundance of methane, which contributes significantly to the mean molecular weight. The second method is based on the direct inversion of infrared spectra and yields values consistent with those from the first method; however, examination of the sensitivities of the two methods indicates that in the Saturnian case the first approach provides more accurate results. Comparison of the helium abundance of Saturn with that of Jupiter and the sun suggests that helium precipitation is significant in Saturn but may not have begun in Jupiter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 282; 807-815
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  • 115
    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 58; 35-73
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  • 116
    Publication Date: 2011-08-18
    Description: Voyager Planetary Radio Astronomy data collected over 30-day intervals centered on the two close encounters with Jupiter were utilized to study the characteristics of millisecond-duration radio bursts (s-bursts) at frequencies between 5 and 15 MHz. In this frequency range, s-bursts are found to occur almost independently of Central Meridian Longitude and to depend entirely on the phase of Io with respect to the observer's planetocentric line of sight. Individual bursts typically cover a total frequency range of about 1.5 to 3 MHz, and they are usually strongly circularly polarized. Most bursts in a particular s-burst storm will exhibit the same polarization sense (either right-hand or left-hand), and there is some evidence for a systematic pattern in which one polarizations sense is preferred over the other as a function of Io phase and Central Meridian Longitude. These data are all suggestive of a radio source that is located along the instantaneous Io flux tube and that extends over a linear dimension of 5000 km along the field lines in both the Northern and Southern Hemispheres. Previously announced in STAR as N84-17109
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 2689-269
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  • 117
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    Publication Date: 2011-08-18
    Description: The gravity anomaly associated with Ishtar Terra on Venus is characterized, comparing line-of-sight acceleration profiles derived by differentiating Pioneer Venus Orbiter Doppler residual profiles with an Airy-compensated topographic model. The results are presented in graphs and maps, confirming the preliminary findings of Phillips et al. (1979). The isostatic compensation depth is found to be 150 + or - 30 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 11; 489-491
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  • 118
    Publication Date: 2011-08-18
    Description: A one-dimensional radiative-convective model is used to compute temperature and water vapor profiles as functions of solar flux for an earthlike atmosphere. The troposphere is assumed to be fully saturated, with a moist adiabatic lapse rate, and changes in cloudiness are neglected. Predicted surface temperatures increase monotonically from -1 to 111 C as the solar flux is increased from 0.81 to 1.45 times its present value. The results imply that the surface temperature of a primitive water-rich Venus should have been at least 80-100 C and may have been much higher. Water vapor should have been a major atmospheric constituent at all altitudes, leading to the rapid hydrodynamic escape of hydrogen. The oxygen left behind by this process was presumably consumed by reactions with reduced minerals in the crust.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 57; 335-355
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  • 119
    Publication Date: 2011-08-18
    Description: The evidence for solid mode 3 particles in the clouds of Venus is reexamined. The sampling characteristics of the cloud particle size spectrometer (LCPS) are reviewed, and reasons are pointed out for believing that relatively small differences in interpreting the measurements of this instrument could produce systematic errors. It is shown that all of the Pioneer Venus and Venera measurements can be understood if it is assumed that the large particles observed by the LCPS form the tail of the mode 2, H2SO4 size distribution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 57; 143-160
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  • 120
    Publication Date: 2011-08-18
    Description: U-Pb age determinations on four lunar zircons from existing thin-sections of one highland breccia, 73217, using the recently constructed ion microprobe SHRIMP, are reported. The analytical reproducibility of SHRIMP is demonstrated, and procedures for measuring Pb/U, Th/U, and corecting for initial Pb are explained. Electron microprobe analyses for the zircons are alsoar reported. The results show that the four zircons survived the lunar cataclysm without any identifiable effects on their U-Pb systematics. All four indicate a single age of 4356 +23 or -14 m.y. The zircons have experienced small variable amounts of Pb loss since crystallization, from almost zero up to about 10 percent. If this occurred during one later event, then age of the latter is between 1100 and 2300 m.y.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; B525-B53
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  • 121
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    Publication Date: 2011-08-18
    Description: The stability of the Venus ionopause is examined in light of the importance of gravitation and curvature. Using a one-fluid approximation for the equation of motion of the plasma, and ignoring the effects of neutrals, a dispersion relation is obtained that includes the effects of the magnetic field, sheared plasma flow, buoyancy, centrifugal force and magnetic tension due to boundary curvature. It is found that buoyancy acts to neutralize the flute instability. As expected, the Kelvin-Helmholtz mode is the dominant instability over most of the dayside ionopause. The expected growth times of this mode are short in comparison with the wave-convection time over the boundary; the waves can grow and saturate quickly, producing a turbulent boundary that may affect electrodynamic coupling between the solar wind and ionospheric plasmas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 997-1002
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  • 122
    Publication Date: 2014-09-27
    Description: Curvilinear features on Mars have dimensions ranging from 0.5 to 18.6 km in length and 0.2 to 2.0 km in width; these landforms can occur as curving ridges and troughs, rimless arcuate depressions, or features with no apparent relief. The Martian curvilinear ground has a relatively consistent relationship to both regional and local geomorphology. These landforms are one of a suite of features that occur near the base of the regional slope that marks the transition from the cratered uplands to the northern plains. Based on morphologic similarities, numerous terrestrial analogs were proposed for these Martian features. These include gilgai, backwasting scarps, solifluction lobes, ice-cored ridges and glacial moraines. Process models for the origin of the curvilinear ground suggest that its formation probably involved several processes, including scarp retreat by backwasting.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 215
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  • 123
    Publication Date: 2014-09-27
    Description: Iapetus is one of the most mysterious objects in the Solar System. As indicated by previous ground-based studies and dramatically confirmed by the Voyager images, the surface of this satellite has a strikingly bimodal distribution of albedo and color. While the underlying object seems to be a largely icy satellite similar to Rhea, the leading hemisphere of Iapetus is dominated by a very dark patch of hemispheric scale. The symmetry of this dark material with respect to the orbital motion of the satellite strongly suggests an external control, if not necessarily an external origin, for the dark material. Quantitative photometric techniques are used to map the photometric function of the surface of the material over Iapetus. The approach is to study clearly defined surface areas that appear on a number of Voyager images obtained under different spacecraft and lighting geometries.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 26
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  • 124
    Publication Date: 2014-09-27
    Description: The Galilean Satellite Geological Mapping Program was established to illuminate detailed geologic relations on the four large satellites of Jupiter. The program involves about 40 investigators from various universities, reseach institutes, and government offices in the United Sttes, England, Germany, and Italy. A total of 24 researchers have been assigned to map 10 quadrangles on Ganymede, 15 to map 6 quadrangles on Io, and 3 to map 2 quadrangles on Europa. All maps are at a scale of 1:5 million except for three of the Io maps, where high-resolution pictures permitted compilation of selected areas at larger scales.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 313
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  • 125
    Publication Date: 2014-09-27
    Description: The evolution of planetesimals in the outer Solar System were evaluated, both stellar and planetary encounters. About 20% of the Uranus-Neptune planetesimals (UNP's) enter the comet cloud and are stored primarily in the region inside the observational limits of the Oort cloud. Half of the comets have suruived to the present time; the cloud now has a mass of the order of Jupiter's mass. Most UNP's are ejected from the Solar system, and about half of the planetesimal swarm is passed to the control of Jupiter prior to ejection. Jupiter's perturbations drive a large flux of these planetesimals into Earth-crossing orbits, and it now appears highly probable that UNP's account for most of the heavy bombardment of the Moon and Earth.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 37
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  • 126
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    Publication Date: 2014-09-18
    Description: The following aspects of the planet Mars are addressed: general properties of the surface, the atmosphere and surface volatiles, craters and crater ages, volcanoes, wind erosion, and the polar regions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL The Geol. of the Terrest. Planets; p 207-264
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  • 127
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    Publication Date: 2014-09-16
    Description: The existence of intense and variable H Ly a emission from Uranus is demonstrated utilizing the monochromatic imaging capabilities of the International Ultraviolet Explorer satellite. A series of 14 observations, using the IUE short wavelength spectrograph in low dispersion and covering the period from 3 March 1982 through 2 September 1983, shows the disk averaged Ly a brightness of Uranus to vary between 690 and 2230 Rayleighs. Model calculations indicates that 400 R of this emission can be attributed to resonant scattering of solar Ly a radiation. An upper limit of 100 R is obtained for the Raman scattering of solar Ly a by H2 (1280 A). This implies that 300 R is contributed to the planetary Ly a emission by Rayleigh scattering. In addition to being unexpectedly strong, the Uranian Ly a emission has been observed to vary by a factor of two in one 24 hr period and by about 50% in one 5 hr period.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL Uranus and Neptune; p 559-572
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  • 128
    Publication Date: 2014-09-16
    Description: The orbital motion of Triton was redetermined from photographic data spanning the interval 1899-1981. The resulting ephemeris should provide Triton positions with respect to Neptune with an accuracy of plus or minus 500 km through the end of the century. The following physical results follow from the orbit solution. The inverse mass of Neptune + Triton is solar mass over (c sub N + m sub T) = 19490 plus or minus 40. No acceleration of the mean motion nor orbital eccentricity were detected, thus constraining the tidal dissipation factors of Neptune and Triton to O sub N less than or equal to 650 and QT less than or equal to 10,000. Tidal heating of Triton is presently insignificant. The gravitational harmonic J sub 2 of Neptune is 0.0043 plus or minus 0.0003 if Triton is as massive as m sub T/ M sub N = 0.00128, and if Neptune's spin is prograde with P approximately 18(h), or J sub 2 = 0.0037 plus or minus 0.0002 if Triton is much less massive. Triton undergoes extreme climatic variations due to the combined motion of it's orbit plane and Neptune's orbital motion. Approximately 10% of Triton's surface is presently hidden from diurnal insolation, which may provide a powerful cold trap for atmospheric voltatiles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Uranus and Neptune; p 357-373
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  • 129
    Publication Date: 2014-09-17
    Description: The detection of the J = 10 manifold of the pure rotational band of PH3 on Saturn is reported. The observations were made from the far-infrared cooled grating spectrometer. The wavelengths and observed brightness temperatures for the full disk plus rings are 89 + or - 3 K at 97.04 micrometer, 77 + or - 3 K at 102.72 micrometer, 77 + or - 3 K at 102.94 micrometer, and 83 + or - 3 K at 105.12 micrometers. The points of 97.04 and 105.12 micrometers establish the continuum level and the two points near 103 micrometers measure the depth of the PH3 manifold. After the flux due to the rings is subtracted, the depth of the feature is 16 + or - 6 K relative to the nearby 102 K continuum. These results are compared to theoretical models which parameterize the PH3 mixing ratio as x = x sub zero (P/P sub zero)(alpha) for P P sub zero and as x = x sub zero for P or = P, where P is the total pressure and alpha = H/h is the ratio of the dynamical scale height (H) and the scale height for decreasing the PH3 mixing ratio (h). The parameters x sub zero, P sub zero, and h were varied, as well as the H/He mixing ratio and the pressure-temperature profile. The data are well fitted using pressure-temperature profiles. The preferred values of h, P sub zero, and x sub zero imply that there is little or no PH3 above the thermal inversion and that the mixing ratio below the inversion is consistent with PH3 being 1 to 4 times overabundant relative to the solar P/H ratio.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Airborne Astron. Symp.; p 76-80
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  • 130
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    Publication Date: 2014-09-17
    Description: The oblateness of a planet is closely related to its rotation rate and internal mass distribution, and is therefore an important indicator of gross planetary structure. Analysis of Stratoscope II images of Uranus yields epsilon = 0.022 + or - 0.001, and stellar occultation observations yield epsilon = 0.024 + or - 0.003. Because of the current pole on aspect of Uranus, it is unlikely that a significantly more accurate value can be determined by stellar occultations before Voyager 2 encounters Uranus in January, 1986. Neptune's oblateness has been determined from stellar occultation observations made in 1968 and 1983. The 1968 observations yield an oblateness of 0.021 + or - 0.004. A recent determination of Neptune's oblateness using both the 1968 and 1983 observations is consistent with this value. Space Telescope observations of several stellar occultations by Neptune could provide a significantly more accurate determination of the oblateness before the Voyager 2 encounter in 1990.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL Uranus and Neptune; p 349-255
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  • 131
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    Publication Date: 2014-09-18
    Description: The present state and evolution of the physical features which are visible on the Moon's surface are emphasized herein. Lunar craters, their distribution and stratigraphy, and the cratering processes are addressed. Homologous material is presented for lunar basins. Terra breccias, maria, and mare basalts are discussed. Lunar geologic history is also considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL The Geol. of the Terrest. Planets; p 107-206
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  • 132
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    Publication Date: 2014-09-18
    Description: The following aspects of the planet Venus are discussed: orbit, rotation, composition, wind erosion, topography, surface roughness, gravity, and tectonics. The Venera satellites, Pioneer space probes, and Mariner space probes involved in Venusian exploration are enumerated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Geol. of the Terrest. Planets; p 57-78
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  • 133
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    In:  CASI
    Publication Date: 2014-09-18
    Description: The nature of comets and asteroids is reviewed briefly. The formation of planets is examined. Meteorites and chondrites a meteoritic subclass, are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL The Geol. of the Terrest. Planets; p 5-12
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  • 134
    Publication Date: 2014-09-17
    Description: Measurement of the abundance and vertical distribution of H2O in Jupiter's atmosphere is discussed. Water was first detected using the Kuiper airborne observatory (KAO) and has also been observed at 5 micrometers by the Voyager infrared spectrometer, IRIS. Studies of H2O in the atmospheres of other planets require special high altitude facilities to reduce the interference of telluric H2O. Jovian H2O absorption lines are overwhelmed by terrestrial H2O at ground-based observatories but they are readily apparent in airborne spectra. Typical column abundances of H2O above ground-based telescopes are about 3000 precipitable micrometers versus only 10 pr micrometers above the KAO at the 12.5 km level. For comparison, there is about 150 pr micrometers H2O above the 3 bar level on Jupiter. Airborne observations also take advantage of cryogenic detectors which have not been used thus far on deep space probes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Ames Research Center Airborne Astron. Symp.; p 69-75
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  • 135
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    Publication Date: 2011-08-18
    Description: New evidence concerning the detailed structure of the magnetic field in and near the Jovian tail sheet is presented, and nonunique temporal variations in the sheet structure are deduced. Data from Voyagers 1 and 2 are used to show that the local sheet structure, while tending to vary with time and distance from Jupiter, generally corresponds to one of four general types. The four types are classified using examples, and possible geometries associated with each type are identified. The locations of the different types of sheet crossings are pointed out and discussed. The possibility of reconnection occurring at the current sheet is discussed through analogy with the terrestrial magnetotail. It is concluded that the results support the view that reconnection occurs in the Jovian magnetotail as a time-dependent, and possibly spatially localized, process.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 57-64
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  • 136
    Publication Date: 2011-08-18
    Description: The spatial distribution of craters 8 km diameter on an area of Callisto are compared with that of a lunar highlands area from which craters are removed to produce the Callisto size/frequency distribution. Craters in the lunar area are mapped and classified according to degradational type using the five-fold LPL scheme where Class 1 is the freshest and Class 5 the most degraded. The size/frequency distribution are determined and compared with the Callisto area. Craters are removed according to the stage of degradation. Its crater population is basically a production population deficient in large craters relative to that of the terrestrial planets. This indicates that the population of impacting objects responsible for the period of heavy bombardment in the inner solar system was different from that at Jupiter, and probably had a different origin as well.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Advan. in Planetary Geol.; p 157-159
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  • 137
    Publication Date: 2011-08-18
    Description: A geologic map of the Ismenius Lacus (MC-5) Southwestern subquadrangle of Mars is described, using the 1:2,000,000 photomosaic as a base. The mapping, and a limited study of the surrounding areas, was done to determine the nature and origin of fretted terrain, fretted channels, and the northern highland scarp. Some highlights resulting from the mapping and accompanying topical investigations are included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Advan. in Planetary Geol.; p 149-151
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  • 138
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    Publication Date: 2011-08-18
    Description: The northeastern section of Thaumasia is located in the heavily cratered southern highlands of Mars between 30 S and 47.5 S and 67.5 W and 90 W. To the northwest lies the Tharis bulge and to the southeast is the Argyre Basin. Previous mapping in Thaumasia included a geologic map of the entire guadrangel by McGill (1978) at a 1:5,000,000 scale and a map of lava flows in the northwest quadrant by Scott and Tanaka (1981). Most investigations concentrated west of 90 W long. in conjunction with the Tharis volcanics. This investigation was designed to examine the overall geology of this section of Thaumasia. After distinguishing various geomorphical units, a geologic map was made at a scale of 1:2,000,000. Lastly, a general sequence of events was developed for the area. Mapping was done from individual low, medium, and high resolution images from the Viking missions, as well as using a 1:2,000,000 scale photo mosaic of the northeast quadrant of Thaumasia. Amount of cratering and faulting, superposition, differences in morphology, and albedo were used to separate out geomorphologically distinct units.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Advan. in Planetary Geol.; p 205-207
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  • 139
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    Publication Date: 2011-08-18
    Description: A compilation of those meteorites currently recognized as being L chondrites, exclusive of the numerous Antarctica finds, was made and is known as the L Chondrite Register. Data for these 576 meteorites was collected from a variety of sources, primarily the British Museum's Catalogue of Meteorites and the Appendix to the Catalogue of Meteorites. Also used was the Revised Cambridge Chondrite Compendium, which provided a convenient listing of L chondrites; other sources include Chinese Meteorites, Meteorites, by Wasson (1974), and the Meteoritical Bulletin of Meteoritics. This last source provided data for most recent falls and was referenced through March of 1982. All such data were recorded on a computer data file with a HP 2647A terminal, so that information could easily be retrieved and manipulated. For each meteorite, the petrographic class, location of find, fall date and hour, mass, mole per cent fayalite, weight per cent Fe, SiO2/MgO ratio, shock class, metal class, 4He abundance, UTh-H3 gas retention age, K-Ar gas retention age, and 21Ne cosmic ray exposure age, was recorded when known.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Advan. in Planetary Geol.; p 167-171
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  • 140
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    Publication Date: 2011-08-18
    Description: Through the use of high resolution Viking topographic data, a hypothesis for the formation of Mangalla Vales is presented. Subsurface water flow and concurrent lava flow are used to explain the theory of a catastrophic flood that created the network of channels. A thorough description of the terrain is included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Advan. in Planetary Geol.; p 153-156
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  • 141
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    Publication Date: 2011-08-18
    Description: The Martian surface thermal characteristics as they effect the thickness and distribution of the permafrost are discussed. Parameters such as temperature mean, maximum, and minimum, heat flow values, and damping depths are derived and applied to a model of the Martian cryosphere. A comparison is made between the permafrost layers of Earth and Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Advan. in Planetary Geol.; p 115-132
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  • 142
    Publication Date: 2011-08-18
    Description: An evaluation of surface features and structures on the Galilean moon Europa is made using the available high resolution Voyager imagery, low resolution support imaging, and what understanding of ice structure and mechanical behavior science has that is applicable to the problem. A general discussion of the history of Europa studies and the fundamental global morphology is undertaken. The visible lineament and terrain patterns are described, and possible origins discussed. Observations of faulting and block rotation previously described are amplified. A comparison of Europa's structures to terrestrial sea ice and lava lake crust features is also included. Finally, an attempt is made at synthesizing a unified model for the evolution of Europa's crust is presented which is compared with models developed by others.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Advan. in Planetary Geol.; p 3-112
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  • 143
    Publication Date: 2011-08-18
    Description: The solar system which had a beginning, 4.6 billion years ago is discussed. The atoms that make up the solar system are much older than that, however: they were also part of the universe that existed before the solar system formed. The presence and location of the atoms of silicon, iron, calcium, that make up the Earth and other planets before there was a solar system is questioned. Astronomical it is shown that they existed in tiny dust grains which, along with molecules of gas, wandered about in the vast reaches of space between the stars of our galaxy. The solar system was formed when one particular cloud of interstellar dust and gas became dense enough to be gravitationally unstable: the gravitational pull that dust grains and gas molecules exerted on one another caused the cloud to collapse.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 56-57
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  • 144
    Publication Date: 2011-08-18
    Description: The magnetite containing spheres collected from a kt boundary localities in Italy were analyzed. It was found that these spheres contain relatively high concentrations of Ir. The spheres were analyzed for siderophile elements Ir, Pt, Au, Pd, Os, and Re. Elements Ir, Pt, Pd, and Au were found in high concentrations in magnetic spheres and their concentrations are similar to those in most meteorites. It is suggested that the magnetite spheres do not contain a meteorite component which may be a relic of the kt event.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 41-44
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  • 145
    Publication Date: 2011-08-18
    Description: A high-resolution (approximately 2 km) image of Beta Regio, Venus, obtained with the Arecibo radar system, reveals additional details of its structure which seem to confirm past suggestions that this region consists of a rift system and associated volcanism. Numerous long linear features approximately parallel to the north-south trending trough discovered by the Pioneer-Venus Orbiter are interpreted as being indicative of extensive faulting and the detail for the radar reflectivity anomaly coincident with Theia Mons suggests that it is a major volcano situated on what would be the western bounding fault of the rift system.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 8-9
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  • 146
    Publication Date: 2011-08-18
    Description: The geology of Venus is discussed. The approximate age of the surface and the relative importance of large scale volcanic, tectonic and sedimentary processes are not known. Venus holds a very important role in comparative planetology. The investigation of comparable environments to Venus to test ideas of landform development on that planet are proposed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 30-33
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  • 147
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    Publication Date: 2011-08-18
    Description: The radar altimetry, roughness (RMS slopes), and reflectivity data acquired for Venus represent the only global radar information available for any of the planets. In addition, the Pioneer Venus radar instrument was able to sound the surface at normal incidence so that it was possible to accurately measure the small-scale surface slopes and reflectivity (dielectric and porosity properties) at the same time as the surface elevation. Analyses of the topography of Venus demonstrate that it differs in its distribution from the Moon, Mars, or the Earth. While the range of topography extends from -2.5 km below the reference level to 11.5 km above, most of Venus falls within 1 km of the mean elevation, this is in sharp contrast to the Earth. The narrow, unimodal nature of the distribution of topography on Venus evidently exerts control on the other radar-derived properties of the surface. When clustering analysis techniques are applied to the Venus radar data sets, the result demonstrates that topographic zones serve as the best criteria for distinguishing regions on Venus which have related radar properties. The individual radar data sets are investigated separately and in conjunction with topography.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 16-19
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  • 148
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    Publication Date: 2011-08-18
    Description: Chondrules which are enigmatic millimeter sized silicate grains embedded in the most common class of meteorites, the chondritic (stony) meteorites. It is shown that the chondritic rocks formed by sedimentation processes in the solar nebula, and that it escaped the subsequent melting processes which differentiated the planets from the meteorite parent bodies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 52-55
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  • 149
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    Publication Date: 2011-08-18
    Description: The most widely accepted theory for lunar evolution is the cumulate remelting model. According to the model, the outer several hundred kilometers of the Moon were molten early in its history at about 4.4 to 4.5 billion years ago. As this magma ocean cooled minerals began to crystallize and accumulate either at the base or the top of the magma ocean depending upon the density of the mineral. The accumulated minerals at the base were partially remelted at about 3.9 to 3.2 billion years to produce the mare basalts.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 47-51
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  • 150
    Publication Date: 2011-08-18
    Description: The most primitive meteorites are called chondrites; which contain small spherules called chondrules. Chondrules and the other ingredients in chondrites appear to have formed long before there were any planets in the solar system. The rocks offer clues to the earliest history of the solar system and an opportunity to understand how some of the small planets were formed, how they were heated and how they were affected by impacts. The origin of asteroids, that supply the meteorites is examined and two factors are proposed: (1) meteorites come from many different bodies that have formed and evolved in slightly different ways, and (2) impacts provide samples of both the surfaces and deep interiors of these bodies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 38-40
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  • 151
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    Publication Date: 2011-08-18
    Description: The distribution fracture patterns of old Martian impact basins were studied. The basaltic plains on the Moon generally occur inside or around impact craters and basins and it is believed that fractures generated by large impacts provided long lasting pathways for magmas. The volcanic plains and volcanic edifices on Mars which show a complex distribution are the interiors of the most obvious old basins are largely buried by wind blown deposits. The Martian ridged plains that most resemble the lunar maria typically are offset from such impact basins. The origin of the mare like plains offset and the placement of the large volcanic mountains are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: 15th Lunar and Planetary Sci. Conf.; p 34-37
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  • 152
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    Publication Date: 2011-08-18
    Description: Inclusions found in type 3 carbonaceous chondrites such as the Allende meteorite are described and compared with those in the Murchison type 2 carbonaceous chondrite. Scanning electron microscope studies of the SH-6 (containing abundant hibonite) and the GR-1 (containing abundant hibonite and corundum) are discussed. Because corundum and hibonite are higher temperature condensates than the melilite and pyroxene found in the Allende meteorite, it is concluded that most refractory inclusions in the Murchison meteorite were isolated from the solar nebular gas at a higher temperature than their counterparts in the Allende meteorite. Whether the inclusion crystallized from a liquid or condensed directly from solar nebular gas is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 20-24
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  • 153
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    Publication Date: 2011-08-18
    Description: The Moon's origin could be deduced with certainty if its bulk chemistry were known. However, determination of this chemistry is difficult because of the profound and complex redistribution of elements that occurred in the outer portions of the Moon during crystallization of the magma ocean. The compositions of 23 varieties of volcanic glass, erupted from depths approaching 300 miles, were used to predict the chemistry of a special glass (genesis glass) having a direct link to primordial lunar matter. A sample of glass with the predicted composition was discovered. This allows a new estimate to be made of the Moon's bulk composition. The data indicate that the Moon shares some intriquing chemical similarities with the Earth's mantle. Both genesis glass and lunar gas are furnishing definitive data on the Moon's composition and origin.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 15th Lunar and Planetary Sci. Conf.; p 8-9
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  • 154
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    Publication Date: 2011-08-18
    Description: The planet-crossing asteroid survey was begun in 1973 in order to study those asteroids which may intersect the orbits of the inner planets. Throughout the history of the survey, many of the various classes of asteroids were investigated. The near-Earth objects including the Apollo, Amor, and Aten families were studied in addition to asteroids whose orbits cross that of Mars, and some objects which are generally confined to the main belt. Observing was done on the 18 inch Schmidt telescope at the Palomar Mtn. Observatory. Typically, two consecutive photographs of a favorable field are taken. The exposure times of the films are usually twenty minutes and ten minutes, respectively. The telescope is guided at sidereal rate, so that asteroids will leave short trailed images. The films are then scanned for trails. By comparing the two films, the direction and approximate rate of motion of an asteroid may be determined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Advan. in Planetary Geol.; p 208-211
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  • 155
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    Publication Date: 2011-08-19
    Description: The widely procedure used for the allowance of nongravitational effects in the motions of comets is summarized. Some results are mentioned, and an innovative variation of the procedure is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL Cometary Astrometry; p 163-166
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  • 156
    Publication Date: 2011-08-18
    Description: The photochemistry of PH3 in the atmosphere of Saturn is studied, including the effects of coupling with the photochemistries of NH3 and hydrocarbons. The vertical concentration of PH3 is found to be extremely sensitive to the eddy diffusion coefficient (K) profile used. If K is roughly 10,000 sq cm/sec in the upper troposphere, PH3 should be depleted there with a scale height of about 3.5 km. An upper limit of 100,000 sq cm/sec is estimated for K. If the gas phase concentration of P2H4 can be neglected, production of molecular phophorus is very unlikely unless the spin-forbidden recombination reaction PH+H2+M - PH3+M occurs with an exceptionally low rate. Coupling of PH3 and hydrocarbon photochemistries is very important. Possible observable amounts of the organophosphorus molecules CH3PH2 and HCP are tentatively predicted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 59; 314-335
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  • 157
    Publication Date: 2011-08-18
    Description: Radiative-convective equilibrium models for Jupiter and Saturn have been produced in a study concentrating on the stratospheric energy balance and the possible role of aerosol heating. These models are compared directly with the thermal structure profiles obtained from Voyager radio occultation measurements. The method is based on a straightforward flux divergence formulation derived from earlier work. The balance between absorbed and emitted energies is computed iteratively at each level in the atmosphere, assuming local thermodynamic equilibrium and employing a standard treatment of opacities. Results for Jupiter indicate that a dust-free model furnishes a good mean thermal profile for the stratosphere when compared with the Voyager 1 radio occultation measurements. Observations of the equatorial region exhibit periodic vertical structure. The Saturn models are relatively simple and in good agreement with the Voyager 2 radio occultation temperature profiles at all levels. Aerosol heating played a minor role in Saturn's midlatitude stratospheric energy balance at the time of the Voyager 2 encounter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 59; 336-366
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  • 158
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    Publication Date: 2011-08-18
    Description: This paper reviews nuclear electric propulsion technology and missions. The science objectives and mission performance of the following five missions are presented: (1) Neptune orbiter, (2) Saturn ring rendezvous, (3) an asteroid sample return, (4) a comet sample return, and (5) an interstellar precursor mission. A short status of the reactor and thermal to electric conversion technologies is given as well as a brief discussion of ion thruster technology. A specific nuclear reactor power system concept is presented that produces 100 kWe and has a mass of about 2600 kg. Mission performance in terms of payload and flight time is presented for all five missions. Heliocentric trajectories are presented for the Neptune orbiter, Saturn ring rendezvous, and Comet Tempel 2 nucleus sample return missions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0007-084X); 37; 395-400
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  • 159
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    Publication Date: 2011-08-18
    Description: Science objectives for a Mars exploration program in the 1990s, set forth by NASA's Committee on Planetary Exploration, are presented. They include: an intensive study of the Martian surface, the exploration of the structure and general circulation of the atmosphere, the exploration of the nature and dynamics of the planet's interior, the nature of Mars's magnetic field, the character of the upper atmosphere and its interaction with the solar wind, and the establishment of the global chemical and physical characteristics of the Martian surface. Several low cost missions, which have been suggested by the Committee for NASA's CORE program, such as the Mars Geoscience Climatology Observer, the Mars Aeronomy Orbiter, and the Mars Surface Network and Surface Probing missions are also covered. Direct Entry-Direct Return and Out-of-Orbit Entry-Orbital Rendezvous and Docking are two versions of a Mars Rover and Sample Return (MRSR) mission discussed in detail. It is concluded that a MRSR mission will require the combination of full Centaur capability, aerocapture at Mars and earth, and direct return to earth to meet major scientific goals. Further studies should be made in orbit assembly, fuel transfer technology, aeromaneuvering, terminal guidance, rover technology, and robotics.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0007-084X); 37; 370-374
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  • 160
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    Publication Date: 2011-08-18
    Description: Increased scientific interest in the structure and composition of Titan's atmosphere, clouds and surface have led to the study of mission options to the Saturnian system with the main goal of placing a probe into the atmosphere of the satellite. Two probe concepts have been studied by NASA: the first concept, a slightly modified Galileo probe capable of withstanding approximately 50 earth G during atmospheric entry heating and deceleration, would consist of a blunted 53 degree, 136-cm-diameter half-angle cone with a hemispherical afterbody, and a descent module containing scientific instruments and a parachute; the second concept, a system designed to provide in situ atmospheric measurements of Titan's organic haze layer, would consist of a probe using a 165-cm deployable graphite fabric decelerator, a 50-cm-diameter cylindrical descent module containing five instruments and a 2.5 m-diameter parachute and a 50-cm-radius spherical nose cap. Although the modified Galileo probe is feasible, its scientific drawback includes its inability to obtain in situ measurements above approximately 100 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0007-084X); 37; 366-369
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  • 161
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    Publication Date: 2011-08-18
    Description: An overview is presented of NASA's plans for the Planetary Observer Program, whose key element is to control the cost of each mission while establishing a long-term, stable base for the planetary sciences. The SSEC (Solar System Exploration Committee) has endorsed the view that many high science priority inner solar system missions are possible through the use of spacecraft derived from existing earth-orbital spacecraft. It has also recommended the application of space hardware such as that used on the Voyager and Galileo missions, development of both a new modular spacecraft for outer planet, comet, and main-belt asteroid missions (Mariner Mark II Program), and a multi-mission operations system to support future missions after the Venus Radar Mapper (VRM), and Galileo. A set of missions for the SSEC's Core Program has been recommended; they include: the VRM, the Mars Geoscience/Climatology Observer, the Comet Rendezvous/Asteroid Flyby, the Lunar Geoscience Orbiter, the Near-Earth Asteroid Rendezvous, the Venus Atmosphere Probe, the Mars Aeronomy Orbiter, the Mars Surface Probe, and the Comet Intercept Sample Return.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0007-084X); 37; 355-360
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  • 162
    Publication Date: 2011-08-18
    Description: Observations of the solar wind close to Jupiter by the Voyager 1 and Voyager 2 spacecraft in 1978 and 1979 are compared with the hectometer-wavelength radio emission from the planet. A significant positive correlation is found between variations in the solar wind plasma density at Jupiter and the level of Jovian radio emission output. During the 173-day interval studied for the Voyager 2 data the radio emission displayed a long-term periodicity of about 13 days, identical to that shown by the solar wind density at Jupiter and consistent with the magnetic sector structure association already proposed for ground-based observations of the decameter-wavelength emission.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 6819-682
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  • 163
    Publication Date: 2011-08-18
    Description: The novel calibrations of the Ca-pyroxene thermometer accomplished by Kretz (1982) and Lindsley (1983) are presently applied to 24 analyzed pyroxenes from 24 H6, L6, and LL6 chondrites. Both thermometers indicate that the H group equilibrated to significantly lower temperature (820-830 C) than the L and LL groups, yielding values of 860 C (Lindsley) to 930 C (Kretz).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 48; 1363-136
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  • 164
    Publication Date: 2011-08-18
    Description: A recent investigation of C2M carbonaceous chondrite meteorite matrices using electron microscopy and High-Resolution Transmission Electron Microscopy (HRTEM) has provided data on the structure and chemistry of Poorly Characterized Phases (PCP). It is suggested that a dominant matrix variety (10 A PCP) has a structure equivalent to iron-rich tochinilite (6Fe0.9S5/Fe, Mg//OHO2/), which consists of coherently intrastratified mackinawite and brucite sheets. In addition, it is proposed that 17 A PCP is a commensurate intergrowth of serpentine and tochinilite layers. Various forms of PCP observed in carbonaceous chondrites appear to be intergrowths of tochinilite, serpentine, and tochinilite-serpentine minerals.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 309; 240-242
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  • 165
    Publication Date: 2011-08-18
    Description: During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densities measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings. Previously announced in STAR as N84-17102
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 2371-237
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  • 166
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    Publication Date: 2011-08-18
    Description: Skylab S-192 multispectral scanner data, in 12 bands covering wavelengths from 0.41 to 2.3 microns, have been investigated to identify and classify geologic units of the lunar surface. Seventeen spectral cluster classes have been identified, seven in the highlands, seven in the maria, and three of which occur in both or in border regions. This finding may be roughly indicative of the relative heterogeneity of these regions. It implies that there is as much heterogeneity in the highlands as in the maria. This work extends the spectral and aerial coverage of similar studies of the lunar surface and provides useful data for comparison for most of the lunar near side.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 57; 241-250
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  • 167
    Publication Date: 2011-08-18
    Description: SEM and TEM, together with thermoluminescence (TL), are used to study five samples of the naturally unshocked Kernouve (H6) meteorite that were shock-loaded to pressures of 70, 165, 270, and 390 kbar. Attention is given to olivine and orthopyroxene deformation mechanisms at these pressure levels. The microhardness of the kamacite in the samples increases with shock pressure, and it is noted that annealed kamacite displays incipient crystallinity, while alpha-martensite and taenite sometimes contain slip lines. At pressures over 200 kbar, there was a systematic decrease in both natural TL and TL sensitivity. Changes in the ratio of these two values for various regions of the TL glow curve suggest that two processes were effective during shock: thermal drainage of electron traps and a reduction in the effective trap density. Thermal effects with widespread annealing are noted in the case of a sample subjected to shock pulse.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 48; 343-360
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  • 168
    Publication Date: 2011-08-18
    Description: Results are presented which strengthen the hypothesis of heterogeneity among the carbon- and nitrogen-bearing phases of the Allende meteorite. These data also highlight the possibility of performing physical separations yielding samples in which some of the noble gas- and carbon-bearing phases are extraordinarily predominant over others. The conclusion, based on mass and isotope balance arguments, that a significant portion of the carbonaceous matter in Allende is likely to be gas-poor or gas-free need not weaken the case for carbonaceous carriers for the major noble gas components. The concept that acid-soluble carbonaceous phases contain a multiplicity of components, each of which may have formed under a multiplicity of different physical-chemical conditions, is reemphasized by the results of the present study.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 48; 267-280
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  • 169
    Publication Date: 2011-08-18
    Description: A detailed study of the Bjurbole fusion crust using scanning electron microscopy (SEM) and energy dispersive analysis (EDS) shows that filamentary crystals and ablation spheres may form on the meteoroid surface. Filamentary crystals, hollow spheres, and porous regions of the surface point to a period of intense vapor phase activity during atmospheric passage. Filamentary crystals can be divided into three categories on the basis of bulk composition and morphology. Two types of filamentary crystals are vapor phase condensation products formed during atmospheric entry of the meteoroid. The other type forms by the interaction of seawater with the fusion surface. The density and composition of ablation spheres varies with the flight orientation of the meteorite. The size range and composition of iron-nickel spheres on the surface of Bjurbole are similar to spheres collected in the stratosphere. A comparison of stratospheric dust collections with meteorite surfaces may provide further insight into the mechanisms of meteoroid entry into planetary atmospheres.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; B597-B60
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  • 170
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    Publication Date: 2011-08-18
    Description: Viking moderate and high resolution images along the northern highland margin have been monoscopically and stereoscopically examined in order to study the development of fretted terrain. Young debris aprons around mesas and debris in tributary channels create typical fretted morphologies identical to ancient fretted morphologies. This suggests that the debris-apron process operating relatively recently also shaped the fretted terrain of the past. The debris aprons were lubricated by interstitial ice derived from ground ice. Abundant collapse features suggest that ground ice existed and may have flowed in places. The fretting process has been active for a long period and may be active today. The location of debris aprons in two latitudinal belts may be controlled by atmospheric conditions that permit ice in the region to remain in the ground below depths of about one meter and temperatures warm enough for ice to flow.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; B409-B41
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  • 171
    Publication Date: 2011-08-18
    Description: Small particles and winds of sufficient strength to move them have been detected from Venera and Pioneer-Venus data and suggest the existence of aeolian processes on Venus. The Venus wind tunnel (VWT) was fabricated in order to investigate the behavior of windblown particles in a simulated Venusian environment. Preliminary results show that sand-size material is readily entrained at the wind speeds detected on Venus and that saltating grains achieve velocities closely matching those of the wind. Measurements of saltation threshold and particle flux for various particle sizes have been compared with theoretical models which were developed by extrapolation of findings from Martian and terrestrial simulations. Results are in general agreement with theory, although certain discrepancies are apparent which may be attributed to experimental and/or theoretical-modeling procedures. Present findings enable a better understanding of Venusian surface processes and suggest that aeolian processes are important in the geological evolution of Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 57; 112-124
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  • 172
    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 48; 111-120
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  • 173
    Publication Date: 2011-08-19
    Description: The geologic, spectral and geochemical characteristics of the lunar Orientale basin are discussed, and a model is defined for the generation of Orientale basin deposits. The data indicate that the basin ejecta is composed mainly of anorthositic deposits and no crustal material. The crater was originally 500-600 km across and 50-60 km deep, the latter being too shallow to reach the projected 100 km crustal depth. A proportional growth model is judged acceptable for the Orientale basin. Finally, it is concluded that neither the Apollo 14 nor 16 missions obtained Orientale ejecta material, which could in any case be unidentifiable until more thorough samplings are made of a large portion of the lunar surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; C197-C21
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  • 174
    Publication Date: 2011-08-19
    Description: The communication of blocky planetary surfaces into fine-grained regoliths was simulated by impacting a fragmental gabbro target 200 times with stainless steel projectiles. It is found that the comminution efficiency of the surfaces changes with time, being highest in the early stages of regolith formation and decreasing gradually. The relationship between mean grain size and cumulative energy is not linear. Individual, fine-grained regolith components can be generated very early from relatively large progenitor fragments without going through intermediate-size fractions. Impact comminution is capable of producing fractionated fines as postulated by Papike et al. (1982). The role of grain-size selective, lateral transport to explain the fractionated nature of lunar regolith fines may have been overestimated in the past.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; C183-C19
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  • 175
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    Publication Date: 2011-08-19
    Description: Venus is the last terrestrial planet to be mapped in the Solar System. This is an indication not of its relative importance for comparative planetary studies but of the previous lack of demonstrated, affordable technology. Venus is, in fact, the most important planet to study for improving our understanding of global terrestrial processes such as plate tectonics. The next NASA mission to Venus, in 1988, will map the planet at a resolution comparable to that of the Mars Mariner 9 mission. The objective is 70 percent coverage at 1 km per line pair or better. This is the minimum resolution that will allow analysis of tectonic, volcanic, aeolian, meteorite impact and other features. An altimeter will provide a global map of topography that will considerably improve our data base and, together with gravity field measurements, provide better interior geophysical models.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0007-084X); 37; 435-441
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  • 176
    Publication Date: 2011-08-19
    Description: It is shown that the most unequilibrated enstatite chondrite, Qingzhen, contains a population of enstatite grains which appear to have formed under more oxidizing nebular conditions than the bulk of the meteorite, which is highly reduced. These grains are black in transmitted light because of the presence of micron-sized inclusions of Ni-poor, Cr-rich metal, and occur either isolated within the matrix or in chondrule interiors. The textural occurrence of these grains argues against their having been introduced during collision of Qingzhen with an oxidized meteorite. Most likely, they originated in the same general nebular neighborhood of the reduced bulk Qingzhen material and were subsequently transported into the reducing environment either before or during the process of chondrule formation. The discovery of this once-oxidized material in Qingzhen posed significant constraints on existing models of formation of reduced matter in the solar system.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 311; 138-140
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  • 177
    Publication Date: 2011-08-19
    Description: The manner in which secular changes in the orbit of the Pioneer Venus Orbiter (PVO) research satellite influence its data collecting capabilities is discussed. A brief description of the propulsion system and sensor arrays of the satellite is presented, and the susceptibility of these systems to changes in power supply due to the decline in solar activity is considered. It is pointed out that the PVO should have enough fuel to continue to transmit data until after the arrival of Comet Halley in 1986, and that, during the 1991 to 1992 period, more moderate levels of solar activity will permit more accurate measurements of thermospheric and ionospheric parameters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: EOS (ISSN 0096-3941); 65
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  • 178
    Publication Date: 2011-08-19
    Description: Sources of organic matter and inorganic tracers on Jupiter, including solar UV photolysis, lightning discharges, and convective quenching of hot gases from the lower atmosphere, are reviewed in light of earth-based and Voyager data with the purpose of predicting the tropospheric steady-state abundances and vertical distributions of HCN, CH2O, and other species. It is concluded that a steady-state mole fraction of HCN in the Jovian troposphere of only about 10 to the -12th could be maintained by vertical transport of hot gases from the deep atmosphere. The observed HCN abundance, roughly X(HCN) = 10 to the -9th, appears to be due to photochemical reactions. After HCN, the most abundant organic-disequilibrium species in the troposphere is probably C2H6, derived from direct photolysis of CH4 at high altitudes, with a mole fraction of about 10 to the -10th at the H2O cloud level. Inorganic tracers of disequilibrium processes are also briefly summarized.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews (ISSN 0038-6308); 39; 163-192
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  • 179
    Publication Date: 2011-08-19
    Description: During the summer of 1979, solar corona structure was such that a sequence of recurrent regions produced a corresponding sequence of corotating solar wind streams with pronounced downstream signatures. One of these stream events passed earth on July 3 and was observed later at Venus late on July 11th, with similar characteristics. Corresponding in situ measurements at earth from the Atmospheric Explorer-E satellite and at Venus from the Pioneer Venus Orbiter are examined for evidence of comparable perturbations of the planetary ionospheres. The passage of the stream shock front is found to be associated with pronounced fluctuations in n(O+) which appear as pronounced local depletion of ion concentrations in both ionospheres. The ionosphere disturbances appear to be closely associated with large variations in the solar wind momentum flux. The implied local ionospheric depletions observed at each planet are interpreted to be the consequence of plasma redistribution, rather than actual depletions of plasma.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 4; 7, 19
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  • 180
    Publication Date: 2011-08-19
    Description: The present investigation is concerned with a comparison of the general observable properties of the radio emission from the earth, Jupiter, and Saturn. Attention is given to typical dynamo spectra, average power, average sense of circular polarization, external control of radio emission, source locations, and emission efficiencies. A data summary regarding planetary radio observations is presented in a table. The polarization of northern hemisphere emission for the three planets is considered along with possibilities regarding the total radiated power of the Uranus radio emission.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Reviews of Geophysics and Space Physics (ISSN 0034-6853); 22; 373-384
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  • 181
    Publication Date: 2011-08-19
    Description: Observations at a wavelength of 1.32 mm have been made of the Jovian planets, Ceres, the satellites Callisto and Ganymede, and the HII region DR 21. The observed brightness temperatures are presented. Those of the Jovian planets agree with the values expected from model atmosphere calculations, except that of Jupiter, which is lower than expected. Ceres and the satellites do not have atmospheres so their emission arised in their subsurface layers. The observed brightness temperatures are intermediate between those measured at infrared and centimeter wavelengths.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 60; 590-598
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  • 182
    Publication Date: 2011-08-19
    Description: An experimental study has been performed to determine whether stresses associated with thermal cycling cracks can affect the coercivity of remanence carried by iron in lunar samples. Initially, samples were cycled up to 100 times in a refrigerator over a period of about 30 min per cycle. In a second set of experiments, samples were dipped directly into liquid nitrogen up to 100 times at about 1 min per cycle. Comparison of AF demagnetization curves of weak field anhysteretic remanent magnetization before and after cycling revealed no systematic differences. Calculations based on a model of spherical iron grains within olivine or troilite indicate that it is unlikely that the iron will crack under thermal stress. Thus, thermal cycling does not appear to provide an explanation for increasing the stability of remanence in samples from the lunar surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 11573-11
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  • 183
    Publication Date: 2011-08-19
    Description: The filling-in of Fraunhofer lines in moonlight has been attributed to lunar luminescence. In order to test mechanisms proposed for this effect, measurements were made of the filling-in of the H-alpha line, the Na D doublet, and a number of lines near the doublet. The degree of filling-in was not correlated with wavelength in a way expected from a broadband luminescence, such as thermoluminescence. However, it was correlated with equivalent width of the Fraunhofer line, such that it increased as equivalent width decreased. This suggests that the Fraunhofer line filling at the moon's surface is caused by inelastic scattering of sunlight with a small wavelength shift, as for example, photon-phonon scattering.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; C240-C24
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  • 184
    Publication Date: 2011-08-19
    Description: Ferromagnetic resonance and magnetic data measured on both sections of the double drive tube cord 64001/2 collected on Stone mountain, station four, Apollo 16 are reported, along with instrumental neutron activation analysis data measured on the lower section. These data provide insight into the depositional and irradiational history and the geochemical provenances of the core.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; C143-C16
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  • 185
    Publication Date: 2011-08-19
    Description: The geology of the Apollo 16 site is reconsidered on the basis of data from photogeology, geochemical remote sensing, and lunar samples. The site possesses an upper surface of anorthositic gabbro and related rocks. Mafic components were deposited as basin ejecta. The events involved in its geological evolution were the Nectaris impact and the Imbrium impact. The role of large, local craters in the history of the region was to serve as topographic depressions to accumulate basin ejecta. The most abundant melt composition at Apollo 16 is an aluminous variety of LKFM basalt supplied by the Nectaris impact as ejected basin impact melt. The mafic LKFM melt may have been supplied by the Imbrium impact. More aluminous melt groups are probably derived from local, small craters. The remainder of the deposits in the region are composed of anorthositic clastic debris derived from the Nectaris basin, the local crustal substrate, and Imbrium and other basins.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; C95-C107
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  • 186
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    Publication Date: 2011-08-19
    Description: The near-nucleus dust coma structure of Comet Halley are studied using modern digital image processing techniques on photographs taken in 1910. Recent investigations carried out in conjunction with the Near-Nucleus Studies Net of the IHW to better understand the characteristics and behavior of Comet Halley are reviewed. A new image processing algorithm developed to enhance coma feature boundaries permits their evolution over as many as three days to be followed. The features can be modeled to derive information on the nucleus spin vector, particle sizes, ejection velocities and distribution of emission areas on the nucleus. Useful contributions by observers in the Astrometry Net are also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL Cometary Astrometry; p 14-20
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  • 187
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    Publication Date: 2011-08-19
    Description: The chemical composition, emission and line spectra, and structure of comet nuclei, cometary atmospheres, and comet tails are discussed. The role of ultraviolet and infrared astronomy in defining comets is examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL Cometary Astrometry; p 7-13
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  • 188
    Publication Date: 2011-08-18
    Description: Analyses of the similarities and differences of the magnetic tails of Venus and Titan are presented. Voyager 1 data showed that the Titan bipolar tail is produced by passage through the subsonic plasma flow of Saturn's magnetosphere. Venera 9 and 10 gathered data on the Venus tail, which is produced by the interaction of the Venus atmosphere and ionosphere with the solar wind. Both nonmagnetic bodies have induced two-lobe magnetic tails, field reversal in the tail and display characteristics of decreased energetic electron densities. The plasma flow is supersonic near the Venus tail boundary but not near Titan. Magnetic merging of the tail lobes is continuous behind Titan and irregular in the Venus tail.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 5461-547
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  • 189
    Publication Date: 2011-08-18
    Description: The infrared absorption spectrum from 3.3 to 27 microns of SO2 ice films has been measured at 20 and 88 K before and after 1-MeV proton irradiation. The radiation flux was chosen to simulate the estimated flux of Jovian magnetospheric 1-MeV protons incident on Io. After irradiation, SO3 is identified as the dominant molecule synthesized in the SO2 ice. This is also the case after irradiation of composite samples of SO2 with sulfur or disulfites. Darkening was observed in irradiated SO2 ice and in irradiated S8 pellets. Photometric and spectral measurements of the thermoluminescence of irradiated SO2 have been made during warming. The spectrum appears as a broad band with a maximum at 4450 A. Analysis of the luminescence data suggests that at Ionian temperatures irradiated SO2 ice would not be a dominant contributor to posteclipse brightening phenomena. After warming to room temperature, a form of SO3 remains along with a sulfate and S8. Based on these experiments, it is reasonable to propose that small amounts of SO3 may exist on the surface of Io as a result of irradiation synthesis in SO2 frosts.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 59; 114-128
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  • 190
    Publication Date: 2011-08-18
    Description: The concept of a quasi-axisymmetric circulation is used to explore the global scale dynamics of planetary atmospheres. A numerical circulation model applicable to Jupiter is presented, and an analytical study is performed elucidating the conditions leading to differential rotation in an atmosphere which is convectively unstable. A linear system forced by solar differential heating is considered, with nonlinear effects arising from advection being represented in the form of eddy diffusion. An empirical, latitudinal spectrum of the observed zonal wind field on Jupiter is discussed. Numerical solutions are presented which reveal banded wind fields with alternating and equatorial zonal jets and a multicellular Ferrel-Thomson meridional circulation consistent with the observed cloud striations on Jupiter. The vertical derivatives are parameterized to construct a simplified one-layer model.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth, Moon, and Planets (ISSN 0167-9295); 30; 245-274
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  • 191
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    Publication Date: 2011-08-18
    Description: Using a linear approximation to the field variation and a mathematical technique for distorting the orbit integration into the complex gyrophase plane, a formula is derived for the nonadiabatic change in magnetic moment. This change varies as the cosine of the particle gyrophase at the equator, so that if a particle traverses the equator several times with different values of this gyrophase, it suffers randomly correlated values for the nonadiabatic change in magnetic moment. The algebraic formula for this nonadiabatic change is found to be in excellent agreement with previous numerical computations. The phase space density, averaged over several bounce periods, is found to satisfy a diffusion equation in pitch angle. The diffusion coefficient is dependent on particle energy, pitch angle, and the field line along which the particles are moving.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 2699-270
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  • 192
    Publication Date: 2011-08-18
    Description: Based on the example of Abernathy (L6 chondrite), it is shown how petrographic investigation can be used to unravel the nature, chronology and conditions of superposed metamorphic events in chondrites. Features considered include the texture of the rock, optical characteristics of olivine, pyroxene and plagioclase, refractive index of plagioclase, metallographical characteristics and microhardness of Fe-Ni alloys. It is deduced that Abernathy has been involved in at least six metamorphic events since the formation of the chondrite. Four distinct shock events and two separate reheating events have been identified. The chronology of these events is established. The conditions for the last four events are reasonably well constrained. These include severe reheating (T greater than 1200 C); severe shock causing complete melting of plagioclase and local melting of the rock (P between 90 and 110 GPa, T between 1250 and 1350 C); mild shock (P between 10 and 25 GPa, T less than 500 C); and reheating below 800 C.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 19; 29-48
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  • 193
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    Publication Date: 2011-08-18
    Description: The Voyager 1 and 2 Planetary Radio Astronomy observations of Jovian decametric radiation (DAM) were transformed into a fixed Io-Jupiter coordinate system for Io longitudes every 10 deg apart starting from 200 to 260 deg (seven plots per spacecaft). An analysis of the data in this coordinate system has shown that the Io-dependent DAM emissions are generated in hollow cones at all frequencies over the fixed Io longitudes studied. The edges of the emission cones are, in many cases, broad in longitude (30 deg or more), with distinct differences found between the characteristics of DAM emission at the edges of the emission cones. The shapes of the DAM emission cones are explained by using three-dimensional ray-tracing calculations within a model Jovian atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Radio Science (ISSN 0048-6604); 19; 556-570
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  • 194
    Publication Date: 2011-08-18
    Description: Comprehensive chemical data are presented on the shergottites Shergotty, Zagami, Allan Hills (ALHA) 77005, and the new member Elephant Moraine (EETA) 79001 using results of sequential instrumental and radiochemical neutron activation analysis. The close relationship of the Antarctic shergotites indicates that ALHA 77005 is a residual source produced by incongruent melting of a source similar in bulk composition to EETA 79001A and that EETA 79001B and the interstitial phases in EETA 79001A are the melts produced by such melting episodes. The large ion lithophile LIL) trace element abundanced of the shergottites require variable but extensive degrees of nomodal melting of isotopically constrained parent sources. The SNG sources are consistent with their derivation by extensive fractionation of a primitive magma initially produced from a source having chondritic refractory LIL trace element abundances. Petrogenetic and age relationships among SNC meteorites suggest a single complex-provenance on a dynamic planet not unlike earth, probably Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; B612-B63
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  • 195
    Publication Date: 2011-08-18
    Description: The suggestion by Nyquist (1983) that shergottites and possibly other SNC (shergottites, nakhlites, and Chassigny) meteorites were launched from the Martian surface by the oblique impact of large meteoroids is further evaluated in the context of the subsequent discovery of a lunar meteorite. It is demonstrated that within calculational uncertainties and the current poorly known fall statistics of lunar and probable Martian meteorites, the oblique impact hypothesis provides a satisfactory explanation of the relative abundances of lunar, Martian, and other meteorites. It is noted that these results support the oblique-impact-on-Mars origin of SNC meteorites and satisfactorily explain the occurrence of a lunar meteorite.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 89; B631-B64
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  • 196
    Publication Date: 2016-03-09
    Description: Various topics on the geology and evolution of the moon, planets, and meteorites are addressed. Some of the subjects considered include: Venusian rocks, impact cratering rate in recent time, ice and debris in Martian fretted terrain, geological evolution of Ganymede's Galileo Regio, and Lu-Hf and Sm-Nd evolution in lunar mare basalts. Also discussed are: ages and cosmic ray exposure history of moon rocks, U-Pb geochronology of zircons from lunar breccia, petrologic comparisons of Cayley and Descartes, chemistry and origin of chondrites and condrules, and the petrogenesis of SNC meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0148-0227)
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  • 197
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: Sample collection and return to the Earth from a fast fly through of a cometary coma is the simplest sample return mission possible from any extraterrestrial body. The mission can provide valuable laboratory samples from a known cometary body and it can do it at low cost, within our lifetimes. The method and the merits of the sample collection process from a comet flyby are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Institute The 47th Ann. Meteoritical Soc. Meeting; 1 p
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  • 198
    Publication Date: 2019-01-25
    Description: The effect of soil formation on the spectral characteristics of asteroids were estimated in situ properties of materials affected by the space environment other than those associated with agglutinates. In his initial survey of the reflectance properties of lunar samples, J.B. Adams measured a few chips from the exterior and interior of Apollo rocks. For Apollo 12 basalts 12053-12063 , the exterior and interior spectra exhibited strong absorption bands which were very similar in nature; the exterior fragment was a bit brighter, which was attributed to microbrecciation. Mature lunar soils measured undisturbed surface areas at the landing sites. It was hypothesized that freshly exposed material at fresh impact craters should be comparable to powdered rock samples in the laboratory. This expected trend seemed to be true with the early reflectance data, but as the more complete near-infrared data has become available it is clear that there is no simple correspondence of rock type (laboratory powder or chip measurement) to freshly exposed surface material (telescopic measurements of fresh crater classes).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Institute The 47th Ann. Meteoritical Soc. Meeting; 1 p
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  • 199
    Publication Date: 2019-01-25
    Description: Deformed chondrules in the Leoville carbonaceous chondrite define a preferred orientation, also recognized previously in other CV3 chondrites. Identifying the strain mechanism is necessary for understanding the conditions which caused this compressional shortening. Luckly, the major mineralogical constituent of CV3 meteorites is olivine, for which experimental data on strain mechanisms exist. The conditions that caused strain in the olivine were obviously applicable to the whole meteorite. Possible mechanisms of olivine deformation are cataclasis, low temperature plasticity, power low creep, and diffusional flow, each of which occurs under different combinations of temperature and deviatoric stress. Cataclasis can be ruled out on the basis of its high deviatoric stress requirements; some fractures occur in chondrule olivines, but these may have formed during excavation or impact. Low temperature plasticity and power low creep occur by means of various types of lattice dislocations. However, methods of thermal decoration and chemical etching of dislocations failed to indicate evidence for either mechanism. Thus, the inference is that diffusional flow, characteristic of low to moderately high temperatures and low deviatoric stress, was the major deformation mechanism.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Institute The 47th Ann. Meteoritical Soc. Meeting; 1 p
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  • 200
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    Unknown
    In:  Other Sources
    Publication Date: 2019-01-25
    Description: Large negative anomalies in Fe, Co, Ni, S and Se are present in Allende Type B Ca-Al-rich inclusions (CAI's). Based on compilations of all the known published analyses, Allende chondrules, aggregates and other types of CAI's also display anomalies. These observations show that: (1) since Fe, Co, Ni, S and Se are more depleted than elements bracketing them in volatility (such as Pt and Au, and Su and Cd), the anomalies were not produced during the volatility dependent, high temperature CAI forming processes; (2) since Pt, Au, Ge and other siderophiles are not as depleted as Fe, Co and Ni, the anomalies are not due to a metal/silicate fractionation; (3) the association of Fe, Co, and Ni anomalies with S and Se anomalies suggests that the anomalies are due to the removal of FeNi sulfide; and (4) since these anomalies occur in all types of Allende inclusions, aggregates and chondrules, the Allende parental material must have undergone sulfide loss before the formation of these components.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Institute The 47th Ann. Meteoritical Soc. Meeting; 1 p
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