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  • LUNAR AND PLANETARY EXPLORATION  (1,391)
  • Organic Chemistry  (1,357)
  • 1995-1999
  • 1990-1994
  • 1980-1984  (1,337)
  • 1975-1979  (1,411)
  • 1980  (1,337)
  • 1977  (1,411)
  • 1929
Collection
Keywords
Publisher
Years
  • 1995-1999
  • 1990-1994
  • 1980-1984  (1,337)
  • 1975-1979  (1,411)
  • 1925-1929  (342)
Year
  • 1
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    The mass of Phobos (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Radio tracking data associated with the February 1977 encounters between the Martian satellite Phobos and the Viking Orbiter I spacecraft have been analyzed to determine the gravitational constant of Phobos. A linear error analysis was conducted to determine the selection of data and the parameter solution set which would yield the best estimate of the gravitational constant. This error analysis indicated that the optimal data set was a data arc beginning just prior to the closest encounter and spanning three consecutive spacecraft orbits; data near periapsis were deleted. The most feasible parameter solution set consisted of the Phobos gravitational constant and the spacecraft initial conditions. The result of the data analysis was an estimate of (7.3 plus or minus 0.7) x 10 to the -4th cu km/sq sec for the gravitational constant of Phobos.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 4; Dec. 197
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  • 2
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    Spectrophotometric and color estimates of the Viking lander sites (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The spectral radiance and color of the Martian sky and soil and the spectral reflectance of soil features are estimated from six-channel (0.4-1.0 micron) spectral data obtained with the Viking lander cameras. Images taken near local noon from the two landers reveal a sky that is brighter near the horizon than the soil but with a similar spectral radiance shape and color. The scenes are predominantly moderate yellowish brown in color with only subtle variations except for some dark grey rocks. Most spectral reflectance estimates are similar: they rise rapidly with increasing wavelength between 0.4 and 0.8 micron and with only a few exceptions exhibit a pronounced minimum centered about 0.93 micron. These characteristics are consistent with an abundance of Fe(3+)-rich weathering products, notably nontronite. However, the delineation of the number and abundances of total mineral phases requires further analyses and laboratory comparisons. Reflectance estimates for rocks have not been repeatable, probably because most rocks have irregular pitted surfaces that introduce significant shadowing components.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Sept. 30
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  • 3
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    A search for ultraviolet OH emission from meteors (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of hydroxyl (OH) emission from meteors were made during the late summers of 1975 and 1976 from altitudes of 10,600 and 14,200 feet (3.2 km and 4.45 km). The observations were made with OH meteor photometers developed at the NASA-Langley Research Center. Two of the meteors were Perseids, and one was an Alpha Capricornid. The Perseid meteors produced a peak irradiance at a distance of 100 km from the meteors of about 0.00005 erg/sq cm per sec in the OH emission region. The zero-magnitude Alpha Capricornid meteor produced a spectral irradiance at 3100 A of 23 hundred-millionths erg/sq cm per A per sec. This may be indicative of significant amounts of H2O in these meteors.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 217
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  • 4
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    Reducing greenhouses and the temperature history of earth and Mars (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It has been suggested that NH3 and other reducing gases were present in the earth's primitive atmosphere, enhancing the global greenhouse effect; data obtained through isotopic archeothermometry support this hypothesis. Computations have been applied to the evolution of surface temperatures on Mars, considering various bolometric albedos and compositions. The results are of interest in the study of Martian sinuous channels which may have been created by aqueous fluvial errosion, and imply that clement conditions may have previously occurred on Mars, and may occur in the future.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 269; Sept. 15
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  • 5
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    Happy Canyon - A new type of enstatite achondrite (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Mineralogical and chemical characteristics of the Happy Canyon meteorite, found in 1971 near Wayside, Texas, show it to be a new type of enstatite achondrite occupying the gap between the recrystallized enstatite chondrites and the igneous, crystalline, unbrecciated enstatite chondrites. Although the bulk composition of the specimen is consistent with that of an E6 enstatite chondrite, it has a crystal cumulate texture. There are minor amounts of metal and troilite which have survived extensive weathering. The Happy Canyon meteorite may represent an E6 composition which has melted and reprecipitated at a slightly higher oxidation state, possibly in the core of a small parent body.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 12; June 30
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  • 6
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    The upper ionosphere of Titan (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Photoionization of the upper atmosphere of Titan by sunlight is expected to produce a substantial ionospheric layer. One-dimensional forms of the mass, momentum, and energy conservation equations for ions and electrons have been solved along with electron number densities of about 1000/cu cm, using various model atmospheres. The significant ions in a CH4-H2 atmosphere are H(+), H3(+), CH5(+), CH3(+), and C2H5(+). Electron temperatures may be as high as 1000 K, depending on the abundance of hydrogen in the high atmosphere. Interaction of the solar wind with the ionosphere is also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 31; May 1977
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  • 7
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    The rings of Uranus (1977)
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    Publication Date: 2011-08-17
    Description: A description is given of the observation of five brief occultations of the star SAO 158687 which occurred both before and after its occultation by Uranus on March 10, 1977. The events were observed with a three-channel occultation photometer, attached to a 91-cm telescope. The observations indicate that at least five rings encircle the planet Uranus. Possible reasons for the narrowness of the Uranus rings are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 267; May 26
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  • 8
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    Observations at the planet Mercury by the plasma electron experiment - Mariner 10 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Two nightside encounters with Mercury's magnetosphere by Mariner 10 revealed bow shock and magnetosheath signatures in the plasma electron data that are entirely consistent with the geometry expected for an interaction between a planet-centered magnetic dipole and the solar wind. The geometrically determined distance between the planet's center and the solar wind stagnation point is 1.4 plus or minus 0.1 R sub M. Both diffuse and sharp shock crossings were observed on the two magnetosphere encounters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; May 1
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  • 9
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    Minor planets and related objects. XXII - Phase functions for /6/ Hebe (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Twenty-two light curves of Hebe are analyzed along with results of UBV photometry and photometric astrometry. A mean synodic period of approximately 7 hr 16 min 28.7 sec is adopted, and it is found that the amplitude of Hebe appears to vary directly with phase. The asteroid's magnitudes and colors are plotted against phase, its pole orientation is estimated, and the sidereal period is determined to be about 7 hr 16 min 28.01 sec from photometric astrometry. A color curve is plotted which shows that Hebe has a reddened region on its surface near the secondary minimum and that the asteroid is nearly spherical. Opposition effects are compared and found to be closely similar for Hebe, Ceres, Lydia, Massalia, and Vesta.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal; 82; Mar. 197
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  • 10
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    The Del Rio ataxite, Texas (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Basic data are presented on the Del Rio, Nordheim, and Monahans ataxites found in Texas. Results are reported for bulk-chemistry analysis, metallographic observations, and electron-microprobe analysis of the Del Rio meteorite. It is shown that Del Rio is distinctly different from the other two ataxites in terms of nickel, phosphorous, and carbon content, and is composed of at least three coarse grains in different crystallographic orientations. All the kamacite in Del Rio is found to have transformation structures that are probable shock products, and minor inclusions of daubreelite, schreibersite, and troilite are observed. It is concluded that Del Rio was apparently mildly shocked prior to its fall.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 12; Mar. 31
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  • 11
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    Wind enhanced planetary escape - Collisional modifications (1977)
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    Publication Date: 2011-08-17
    Description: Effects of collisions and finite winds characteristic of a highly perturbed atmosphere on the thermal escape of terrestrial hydrogen and helium are investigated using a Monte Carlo approach. The limiting cases of vertical and horizontal winds are considered, and the relaxation layer between the collisionless exosphere and the collision-dominated thermosphere is modeled as a plane-parallel slab of given column density, depth, and atmospheric density. For both gases, the upwardly injected flux at the base of the relaxation layer is compared with the returning downward flux distribution at the same location; the technique is also applied to the atmosphere of Titan. The results show that inclusion of collisions in the escape model for terrestrial hydrogen with winds effectively throttles the escape process, that collisional throttling is negligible for helium when the exobase temperature is at least 5000 K, and that the escape of a planetary-atmosphere constituent depends on the ratio of its gravitational and kinetic energies as well as on the ratio of its mass to that of the background gas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Mar. 1
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  • 12
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    A low-frequency radio survey of the planets with RAE 2 (1977)
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    Publication Date: 2011-08-17
    Description: Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer 2 (RAE 2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025-13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Mar. 1
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  • 13
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    Lunar soil - Iron and titanium bands in the glass fraction (1977)
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 195; Mar. 11
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  • 14
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    On the reality of the Venus winds (1977)
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    Publication Date: 2011-08-17
    Description: The article presents a rebuttal of Young's (1975) view that the 140 m/sec horizontal wind at 45 km reported by Venera 8 is anomalous or spurious. Some errors are discussed and the largest contribution is attributed to descent probe measurements designed to find the true probe descent rate. Young's suggestion of error in in situ measurement of winds due to selection of a reference speed and to unrecognized oscillator drift is scrutinized. Evidence is seen for a wide band of variable high-grade retrograde horizontal winds girdling Venus at the equator. Mariner 10 evidence (UV photographs) is taken into account. The band of winds at 45 km is seen to extend well beyond the top of the visible cloud, and an upper turbulent region is attributed to vertical convection currents carried along by high-speed horizontal winds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 30; Feb. 197
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  • 15
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    Saturn - Origin and composition of its inner moons and rings (1980)
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    Publication Date: 2011-08-18
    Description: Theoretical modelling of the contraction of the primitive protosaturnian cloud, using ideas of supersonic turbulent convection, suggests that each of Saturn's inner moons, excepting Rhea, condensed above the ice-point of water and consists primarily of hydrous magnesium silicates. It is predicted that Voyager 1 may find that the satellite mean densities steadily increase towards the planet and that the rocky moons are irregular in shape.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Physics Letters; 80A; Nov. 24
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  • 16
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    Gravity anomalies on Venus (1980)
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    Publication Date: 2011-08-18
    Description: Doppler radio tracking of the Pioneer Venus orbiter has provided gravity measures over a significant portion of Venus. Feature resolution is approximately 300-1000 km within an area extending from 10 deg S to 40 deg N latitude and from 70 deg W to 130 deg E longitude (approximately equal to 200 deg). Many anomalies were detected, and there is considerable correlation with radar altimetry topography (Pettengill et al., 1980). The amplitudes of the anomalies are relatively mild and similar to those on earth at this resolution. Calculations for isostatic adjustment reveal that significant compensation has occurred.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 198
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  • 17
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    Distribution and source of the UV absorption in Venus' atmosphere (1980)
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    Publication Date: 2011-08-18
    Description: The model predictions were compared with the Pioneer Venus probes and orbiter to determine the composition of the UV absorbing materials. The simulations were carried out with radiative transfer codes which included spacecraft constraints on the aerosol and gas characteristics in the Venus atmosphere; gaseous SO2 (a source of opacity at the wavelengths below 0.32 microns), and a second absorber (which dominates above 0.32 microns) were required. The UV contrast variations are due to the optical depth changes in the upper haze layer producing brightness variations between equatorial and polar areas, and to differences in the depth over which the second UV absorber is depleted in the highest portion of the main clouds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 18
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    Measurements of thermal structure and thermal contrasts in the atmosphere of Venus and related dynamical observations - Results from the four Pioneer Venus probes (1980)
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    Publication Date: 2011-08-18
    Description: The thermal structure of the Venus atmosphere and differences in structure with latitude (up to 60 deg) and clock hour (from midnight to 8 AM) have been measured in situ from a height of 126 km to the surface by instruments on the four Pioneer Venus entry probes. It is found that thermal contrasts below 45 km are a few K, with the midlatitudes warmer than both equatorial and high latitudes. Considerable temperature and pressure differences with latitude develop in the clouds (25 K and 20 mbar level). In addition, upward of 110 km, there is evidence of large-amplitude temperature oscillations with altitude, believed to signify the presence of large-amplitude waves, perhaps thermal tides. Agreement of structure data from other Pioneer Venus experiments is generally excellent.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 19
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    Dust in Jupiter's magnetosphere. I - Physical processes. II - Origin of the ring. III - Time variations. IV - Effect on magnetospheric electrons and ions (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The physical processes acting on charged microscopic dust grains in the Jovian atmosphere involve electromagnetic forces which dominate dust particle dynamics and diffusion across field lines resulting from random charge fluctuations of the dust grains. A model of the Jovian ring hypothesizes that the 'visible' ring particles are produced by erosive collisions between an assumed population of kilometer-sized parent bodies and submicron-sized magnetospheric dust particles. Fluctuations in the ring topology and intensity are determined over various time scales, showing that the ring is a quasipermanent and quasistable characteristic of the Jovian system. Finally, the interaction of the Jovian energetic belt electrons and the Jovian plasma with an ambient dust population is examined; the distribution of dust ejected from Io in the inner magnetosphere and losses of magnetospheric ions and electrons due to direct collisions with charged dust particles are calculated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science; 28; Dec. 198
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  • 20
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    Io control of Jovian radio emission (1980)
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    Publication Date: 2011-08-18
    Description: The possibility of Io controlling Jovian decametric radio emission, particularly in the region below 22 MHz, is discussed. Results of a two-year survey at 26.3 at 26.3 MHz are presented which demonstrate the control of Io over a high-intensity storm component of the radio emission and the independence of a weak radio component from the phase of Io, as was observed at lower frequencies. It is thus hypothesized that Io control is a flux-dependent rather than a frequency-dependent phenomenon, and results of analyses at 18 and 10 MHz which support this hypothesis are presented. The apparent correlation between frequency and Io control is thus shown to result from a selection effect due to the increase of non-Io emission with decreasing frequency and relative antenna detection threshold. This result implies a contiguous Io-controlled source region extending out several Jovian radii along the Io flux tube.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 287; Oct. 30
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  • 21
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    Viscous flow and crystallization behavior of tektite glasses (1980)
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    Publication Date: 2011-08-18
    Description: The variation of viscosity with temperature was determined in the 200-2000 K range for a Muong Nong tektite material. The viscosity at the liquidus temperature of 1320 C is 20,000 P; treatments between 900 and 1300 C do not result in significant crystallization in the natural sample except when the sample is heated in contact with a synthetic tektite composition. Two synthetic microtektite with lower SiO2 contents than the Muong Nong material were also examined; heat flow calculations were performed for 2.5 to 10 cm spheres of tektite when cooling by radiation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Oct. 10
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  • 22
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    The occurrence rate, polarization character, and intensity of broadband Jovian kilometric radiation (1980)
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    Publication Date: 2011-08-17
    Description: The paper describes the major observational features of one new component of Jupiter's radio emission spectrum, the broadband kilometer wavelength radiation, or bKOM. This study, using the Voyager Planetary Radio Astronomy (PRA) experiments, reveals that the overall occurrence morphology, dynamic spectra, and polarization character of bKOM are strong functions of the latitude and/or local time geometry of the observations. The postencounter data show a decline in the mean occurrence rates and power level of bKOM and, in particular, a depletion in the occurrence rate at those same longitudes where the detection rate is a maximum before encounter. Additionally, the polarization sense undergoes a permanent reversal in sign after encounter, whereas the time-averaged wave axial ratio and degree of polarization remain relatively unchanged. Finally, no evidence of any control by Io is found. The strong dependence of the morphology on local time suggests a source whose beam is nearly fixed relative to the Jupiter-sun line
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Aug. 1
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  • 23
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    The case against UV photostimulated oxidation of magnetite (1980)
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    Publication Date: 2011-08-17
    Description: The kinetics of magnetite oxidation in O2-bearing atmospheres in the presence of electromagnetic radiation was studied. No perceptible oxidation of magnetite by ultraviolet (UV) photostimulation occurred. These results do not corroborate previous conclusions by Huguenin (1973, 1974) as to the occurrence of this process. Therefore, although the possibility that the process actually occurs cannot be ruled out, it is concluded that there is not yet a basis in laboratory experiments for inferring that UV photostimulated oxidation of magnetite occurs naturally on the surface of Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Aug. 198
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  • 24
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    Voyager detection of nonthermal radio emission from Saturn (1980)
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    Publication Date: 2011-08-17
    Description: The planetary radio astronomy experiment on board the Voyager spacecraft has detected bursts of nonthermal radio noise from Saturn occurring near 200 kilohertz, with a peak flux density comparable to higher frequency Jovian emissions. The radiation is right-hand polarized and is most likely emitted in the extraordinary magnetoionic mode from Saturn's northern hemisphere. Modulation that is consistent with a planetary rotation period of 10 hours 39.9 minutes is apparent in the data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 209; Sept. 12
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  • 25
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    Investigation of numerical properties of Hovenier's exit function equation for multiple scattering of light (1980)
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    Publication Date: 2011-08-17
    Description: A technique of deriving Hovenier's exit function equation (1978) for multiple scattering, starting with a set of invariant imbedding equations, is presented. The feasibility of the exit function equation as a means to obtain reflection and transmission functions is investigated for isotropic, Rayleigh, and Henyey-Greenstein phase functions with emphasis on the numerical stability, accuracy and timing. It is possible to compute the reflection function rather accurately with an efficiency comparable to that of the standard doubling technique for the same phase functions with moderate anisotropy. The resulting transmission is slightly less accurate than the reflection function, but it may be acceptable for practical purposes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysics and Space Science; 69; 1, Ma; May 1980
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  • 26
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    Instability of equatorial protons in Jupiter's mid-magnetosphere (1980)
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    Publication Date: 2011-08-17
    Description: Two different models for the distribution function are fit to the Jovian protons seen by Pioneer 10 inbound. The models reproduce the observed energy and angular distributions. These models are then used to assess the collisionless mirror instability. Because of the pancake proton angular distributions in the equatorial ring current region, the ring current particle population appears to be mirror unstable at times, with instability growth rates of about 10 min. Such a time is consistent with observed proton flux autocorrelation times. An instability such as this (there are other candidates) may be responsible for the previously established proton flux flowing parallel to the magnetic field away from the equatorial region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Jan. 1
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  • 27
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    Saturn's rings - Particle composition and size distribution as constrained by observations at microwave wavelengths. II - Radio interferometric observations (1980)
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    Publication Date: 2011-08-18
    Description: Theoretical models are presented of the brightness of Saturn's rings at microwave wavelengths (0.34-21.0 cm) including both intrinsic ring emission and diffuse scattering by the rings of the planetary emission. In addition, several previously existing sets of interferometric observations of the Saturn system at 0.83, 3.71, 6.0, 11.1, and 21.0 cm wavelengths are analyzed. A comparison of models and experimental data make it possible to establish improved constraints on the properties of the rings. In particular, it is found that (1) the maximum optical depths in the rings is 1.5 + or - 0.3 referred to visible wavelengths; (2) a significant decrease in ring optical depths from 3.7 to 21.0 cm makes it possible to rule out the possibility that more than 30% of the cross section of the rings is composed of particles larger than about a meter; and (3) the ring particles cannot be primarily of silicate composition (independently of particle size), and the particles cannot be primarily smaller than about 0.1 cm, independently of composition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Dec. 198
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  • 28
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    Greenhouse models of Venus' high surface temperature, as constrained by Pioneer Venus measurements (1980)
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    Publication Date: 2011-08-18
    Description: Recent measurements conducted from the Pioneer Venus probes and orbiter have provided a significantly improved definition of the solar net flux profile, the gaseous composition, temperature structure, and cloud properties of Venus' lower atmosphere. Using these data, we have carried out a series of one-dimensional radiative-convective equilibrium calculations to determine the viability of the greenhouse model of Venus' high surface temperature and to assess the chief contributors to the greenhouse effect. New sources of infrared opacity include the permitted transitions of SO2, CO, and HCl as well as opacity due to several pressure-induced transitions of CO2. We find that the observed surface temperature and lapse rate structure of the lower atmosphere can be reproduced quite closely with a greenhouse model that contains the water vapor abundance reported by the Venera spectrophotometer experiment. Thus the greenhouse effect can account for essentially all of Venus' high surface temperature. The prime sources of infrared opacity are, in order of importance, CO2, H2O, cloud particles, and SO2, with CO and HCl playing very minor roles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 29
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    Cloud morphology and motions from Pioneer Venus images (1980)
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    Publication Date: 2011-08-18
    Description: The horizontal and vertical cloud structures, atmospheric waves, and wind velocities at the cloud top level were determined by the Pioneer Venus photopolarimeter images in the UV from January through March 1979. The images indicate long-term evolution of cloud characteristics, the atmospheric dynamics, and rapid small changes in cloud morphology. The clouds show a globally coordinated oscillation relative to latitude circles; retrograde zonal winds of 100 m/s near the equator are determined from the tracking of small-scale cloud properties, but two hemispheres show important variations. The zonal wind velocity in the southern hemisphere is reduced toward the poles at a rate similar to solid body rotation; the midlatitude jet stream noted by Mariner 10 is not observed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 30
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    Pioneer Venus gas chromatography of the lower atmosphere of Venus (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A gas chromatograph mounted in the Pioneer Venus sounder probe measured the chemical composition of the atmosphere of Venus at three altitudes. Ne, N2, O2, Ar, CO, H2O, SO2, and CO2 were measured, and upper limits set for H2, COS, H2S, CH4, Kr, N2O, C2H4, C2H6, and C3H8. Simulation studies have provided indirect evidence for sulfuric acid-like droplets and support the possibility of water vapor at altitudes of 42 and 24 km. The paper discusses the implications of these results for the origin, evolution, and present state of Venus' atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 31
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    Dynamic properties of the thermosphere inferred from Pioneer Venus mass spectrometer measurements (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The data obtained by the Pioneer Venus spectrometer experiments indicate that the day-night temperature contrast on Venus is associated with wind velocities of about 200 m/s which transport oxygen, helium, and hydrogen toward the night side. A mass exchange with the mesosphere commensurate with an eddy diffusion coefficient of 3 x 10 to the 7th is required to buffer the horizontal advection so as to reproduce the observed day time bulge in oxygen and the small diurnal variations in helium. The observed time response and magnitude of the day-night density variations require transport processes to be effective over time periods between five and ten days, implying a superrotation rate or prevailing winds in excess of 50 m/s at the equator. Nonlinear mass transport results in wave steepening and contributes to the amplification of the density extrema in hydrogen and helium.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 32
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    Electron temperature and heat flow in the nightside Venus ionosphere (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A steady-state two-dimensional heat balance model is used to analyze the night side Venusian ionospheric electron temperatures given by the Pioneer Venus orbiter electron temperature probe. The energy calculation includes the solar EUV heating at the terminator, electron cooling to ions and neutrals, and heat conduction within the ionospheric plasma. An optimum magnetic field is derived by solving for the heat flux directions which force energy conservation while constrained by the observed temperatures within the range of 80-170 deg solar zenith angle and 160-170 km. The heat flux vectors indicate a magnetic field that connects the lower night side ionosphere to the day side ionosphere, and connects the upper ionosphere to the ionosheath. The lower ionosphere is heated through conduction of heat from the dayside, and the upper ionosphere is heated by the solar wind in the ionosheath with heat flowing downward and from the nightside to the day side.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 33
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    Mass spectrometric measurements of the neutral gas composition of the thermosphere and exosphere of Venus (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The neutral gas composition and density in the thermosphere of Venus is being measured with a quadrupole mass spectrometer on the Pioneer Venus orbiter. Data are obtained near periapsis once per day approximately 150-250 km above the surface. The principal gases in the thermosphere are CO2, CO, N2, O, N, and He. Atomic oxygen is the major constituent above 155 km on the dayside and also on the nightside up to 180 km when helium becomes the major constituent. The average values of CO2, CO, N2, O, and N remain nearly constant during day and night, but an abrupt change occurs across the terminator from a high dayside value to a low nightside value. The helium density varies in the opposite way, and a distinct bulge was observed at night near the morning terminator. The data have been used as the basis of an empirical model. Large orbit to orbit variations in densities were also observed on the nightside, suggesting perhaps strong turbulent motion in the atmosphere below. Kinetic temperatures inferred from scale heights are approximately 285 K on the dayside and 110 K at night. The average global temperature obtained from the model is 199 K.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 34
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    Empirical models of the electron temperature and density in the Venus ionosphere (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The electron temperature and density of the Venus ionosphere is characterized using data from the Pioneer Venus orbiter electron temperature probe experiment for the full range of solar zenith angles and local times. Values for the electron density are nearly uniform across the day side with a sharp decrease in the vicinity of the terminator. The model shows a substantial night side ionosphere which can be accounted for by a combination of several transport processes, and by local production by precipitating particles. The electron temperature model demonstrates the high temperatures seen on both the day side and night side. It is found that the night side is much more variable than the day side, and that there is no obvious north-south asymmetry in either the temperature or the density.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 35
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    Global observations of the composition and dynamics of the ionosphere of Venus - Implications for the solar wind interaction (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The in-situ measurements of the global composition and Venus ionosphere dynamics recorded by the Bennett ion mass spectrometer on the Pioneer Venus orbiter during Dec. 1978-Aug. 1979 are presented. The observations of three plasma regimes show the bowshock-ionosheath region, the thermal ionosphere, and a superthermal flowing ion layer contacting the ionosphere at the ionopause and extending outward to different heights above the planet. An abundant ionosphere dominated by O(+) above 200 km and by O2(+) down to the typical periapsis altitudes of 160 km occur during quiet periods; less disturbed data shows strong day to night changes in the distributions of ions including O(+), O2(+), CO2(+), and N(+). The ionopause is located near the subpolar point at 250-400 km; under disturbed nighttime conditions it may have randomly spaced concentration gradients in the dusk region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 36
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    Dynamical response of the dayside ionosphere of Venus to the solar wind (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Dayside ion composition measurements made by the orbiter ion mass spectrometer and the orbiter electron temperature probe on the Pioneer Venus orbiter are used to infer the dominant processes involved in the dynamic response of the Venus ionosphere to the solar wind. The analysis is confined to the topside ionosphere in the vicinity of the subsolar point, where the ionosphere-solar wind interaction is expected to be maximized. Height profiles of the ion composition and plasma temperatures in the main body of the topside ionosphere, lying between the ionopause and chemical equilibrium regions, reveal that the ionosphere is in a compressed state. This region of the ionosphere is interpreted in terms of a stationary equilibrium where the compression is derived from the ponderomotive force j x B. The estimated magnitude of this force is confirmed by the magnetic field measurements made by the orbiter magnetometer.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 37
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    Pioneer Venus plasma observations of the solar wind-Venus interaction (1980)
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    Publication Date: 2011-08-18
    Description: Collection of data from the Ames plasma analyzer on the Pioneer Venus orbiter has permitted long-term measurements of the interaction of the solar wind with Venus. The paper presents a mapping of the ionosheath flow field, plasma measurements in the distant ionosheath and near the distant plasma cavity, and a summary of observations of jumps in the solar wind proton parameters across Venus' bow shock. Also, the apparent detection of ionospheric O(+) accelerated up to solar wind speeds downstream in Venus' ionosheath is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 38
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    A physical model of Titan's clouds (1980)
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    Publication Date: 2011-08-18
    Description: A physical model of the formation and growth of aerosols in the atmosphere of Titan has been constructed in light of the observed correlation between variations in Titan's albedo and the sunspot cycle. The model was developed to fit spectral observations of deep methane bands, pressures, temperature distributions, and cloud structure, and is based on a one-dimensional physical-chemical model developed to simulate the earth's stratospheric aerosol layer. Sensitivity tests reveal the model parameters to be relatively insensitive to particle shape but sensitive to particle density, with high particle densities requiring larger aerosol mass production rates to produce compatible clouds. Solution of the aerosol continuity equations for particles of sizes 13 A to about 3 microns indicates the importance of a warm upper atmosphere and a high-altitude mass injection layer, and the production of aerosols at very low aerosol optical depths. Limits are obtained for the chemical production of aerosol mass and the eddy diffusion coefficient, and it is found that an increase in mass input causes a decrease in mean particle size.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 43; Sept
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  • 39
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    Hg and Pt-metals in meteorite carbon-rich residues - Suggestions for possible host phase for Hg (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Carbon-rich and oxide residual phases have been isolated from Allende and Murchison by acid demineralization for the determination of their Hg, Pt-metal, Cr, Sc, Co, and Fe contents. Experimental procedures used eliminated the possibility of exogenous and endogenous contaminant trace elements from coprecipitating with the residues. Large enrichments of Hg and Pt-metals were found in Allende but not in Murchison residues. Hg-release profiles from stepwise heating experiments suggest a sulfide as the host for Hg. Diffusion calculations for Hg based on these experiments indicate an activation energy of 7-8 kcal/mol, the same as that for Hg in troilite from an iron meteorite. This is further support for a sulfide host phase for Hg. Equilibration of Hg with this phase at approximately 900 K is indicated. Reasons for the presence of Pt-metals in noncosmic relative abundances are explored.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 44; Oct. 198
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  • 40
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    Endemic isotopic anomalies in titanium (1980)
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    Publication Date: 2011-08-18
    Description: Abundances of the titanium isotopes were determined using a new high-precision technique that shows terrestrial, lunar, and bulk meteorite samples to be indistinguishable. Ca-Al-Ti-rich inclusions in the Allende meteorite are found to contain Ti of widely varying isotopic composition reflecting the presence of at least three nucleosynthetic components. The anomalies in Ti appear to be relatively widespread and, when correlated with Ca data, provide a clue to nucleosynthesis in the neighborhood of the iron peak and to the late-stage nucleosynthetic processes which immediately preceded formation of the solar nebula.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 240
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  • 41
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    Structures far from the head of comet Kohoutek. II - A discussion of the Swan Cloud of January 11 and of the general morphology of cometary plasma tails (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Photographs show that the 'Swan Cloud' observed in comet Kohoutek on January 11, 1974 was an advanced stage of a plasma tail disconnection event, of which the rejected tail appeared to decelerate as it receded from the head. The event commenced with the development of strong tail ray activity followed by the actual tail disconnection, the merging of the disconnected tail with the new tail to form the Swan and the formation of arcade loops in the space between closing tail rays. The observed morphological sequence is easily understood in the sector boundary model (Niedner et al., 1978), and the arcade loops are proposed to be reconnected flux tubes between oppositely polarized tail rays in the incipient new tail which followed the disconnection
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 42; May 1980
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  • 42
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    Some diurnal properties of clouds over the Martian volcanoes (1980)
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    Publication Date: 2011-08-17
    Description: The diurnal properties of cloud systems over Martian volcanoes observed by the Viking Orbiter spacecraft are discussed. Photographic sequences of diurnal cloud development are presented for clouds in the vicinity of Elysium Mons and Ascraeus Mons, and the rapid growth of cloudiness starting at 11.23 LT is noted. The low-lying fogs and convective afternoon clouds observed are characterized as water ice clouds, while the cirrus-type clouds may be composed of CO2. The diurnal development of the clouds is then explained in terms of local atmospheric stability and circulation as influenced by surface topography and thermal properties. Consideration is also given to possible reasons for the pronounced seasonal variations in cloudiness.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 286; July 24
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  • 43
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    Saturn - Tropospheric ammonia and nitrogen (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Photochemical calculations based on recent data on the Saturn temperature structure and Lyman-alpha albedo indicate that detectable amounts of gaseous ammonia may exist between 20 and 35 km above the cloud tops. An instrument that might be able to observe this gas is the spectrometer on board the International Ultraviolet Explorer satellite. The calculations also yield a maximum nitrogen mixing ratio at the cloud tops between 1.8 x 10 to the -10th to 6 x 10 to the -8th by volume, depending upon the degree of supersaturation of ammonia and hydrazine. Even the lower limit could produce intense emissions if electrical discharges such as those observed on Jupiter by Voyager are also present on Saturn, or if high energy particles penetrate to the Saturnian troposphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; June 198
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  • 44
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    Thermal diffusion calculations for the ionosphere of Venus (1980)
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    Publication Date: 2011-08-17
    Description: Simplified multicomponent diffusion calculations are made for the ionosphere of Venus. Large differences in temperature between electrons and ions and appreciable temperature gradients that are near those of recent measurements are used. Compositions for which binary thermal diffusion coefficients for ions are the same as multi-ion ones are examined as well as those that are quite different. An attempt to combine binary coefficients to give multi-ions ones has not been particularly successful.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Jan. 1
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  • 45
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    Comment on absorbing regions in the atmosphere of Venus as measured by radio occultation (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Dec. 198
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  • 46
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    Evolution of Io's volatile inventory (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Voyager data are used to make crude estimates of the rate at which Io loses volatiles, by a variety of processes, to the surrounding magnetosphere, for the case of both the current, SO2-dominated atmosphere and hypothetical paleoatmospheres in which such other gases as N2 may have been the dominant constituent. Among the mechanisms making significant contributions to the prodigious rate at which Io is losing volatiles are: the interaction of the magnetospheric plasma with volcanic plume particles and the background atmosphere; the sputtering of ices on the surface, if the nightside atmospheric pressure is low enough; and Jeans' escape of O as a dissociation product of SO2 gas. It is also argued that in the case of paleoatmospheres only the first two alternatives would have been possible and, nevertheless, insufficient to account for N2 loss over the life of the satellite.
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  • 47
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    The clouds of Venus - A synthesis report (1980)
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    Publication Date: 2011-08-18
    Description: The results presented represent a synthesis of data from those Pioneer Venus experiments directed toward studying cloud problems. These orbiter and multiprobe experiments show the cloud system to consist of three altitude regions populated by cloud particles and smaller haze particles which extend above and below as well as coexist with the cloud particles. The optical properties derived are only consistent with the largest particles, having platelike morphology. The smallest particles are shown to require changes in chemical composition to explain observed behavior. The medium-sized H2SO4 droplets of 2 micrometers diameter appear to be the least volatile and are the best understood. The role of the cloud particles in precipitation dynamical processes, lightning, and radiation are all discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 48
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    The thermal balance of Venus in light of the Pioneer Venus mission (1980)
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    Publication Date: 2011-08-18
    Description: Pioneer Venus orbiter and probes measured many of the properties of the Venus atmosphere which control its thermal balance and support its high surface temperature. Estimates based on orbiter data yield an effective radiating temperature of Venus of 228 + or - 5 K, corresponding to a solar emission of 153 + or - 13 W/sq cm. A mode of submicron particles is suggested as an important source of thermal opacity near the cloud tops to explain the orbiter and probe thermal flux measurements. A comparison of the measured solar flux profile with thermal fluxes computed from the measured temperature structure and composition shows that the greenhouse mechanism explains essentially all of the 500-K difference between the surface and radiating temperatures of Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 49
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    The structure of the clouds of Venus - Results of the Pioneer Venus nephelometer experiment (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The nephelometer measurements by the four Pioneer Venus probes reveal an upper haze area in the vertical cloud structure with several less clearly delineated layers in the main cloud bank. Concentrated sulfuric acid is the main component of the majority of the particulate matter in the clouds; the near UV radiation is absorbed by the clouds. The particles ejected from the planet surface are in the 10 to 100 micron range.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 50
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    Venus upper atmosphere structure (1980)
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    Publication Date: 2011-08-18
    Description: Atmospheric densities of Venus were measured from the orbital decay of the Pioneer Venus from Dec. 9, 1978 to Aug. 7, 1979 near the 16 deg latitude between 140 and 190 km during the entire day. Comparative atmospheric densities on earth at 150 km are higher by a factor of 3.5 with only a 1% diurnal variation; an atmospheric composition, temperature, and density model based on the orbiter atmospheric drag (OAD) vertical structure is presented. The model shows that atomic oxygen is the major component in the Venus atmosphere above 145 km at night and above 160 km during the day with mixing ratios over 0.1 near 140 km; drag measurements indicate O concentrations from 1 x 10 to the 9th/cu cm in daytime to 3 x 10 to the 7th/cu cm at night. It is concluded that the neutral upper atmosphere of Venus is surprisingly insensitive to solar extreme UV variations and changes in the solar wind.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 51
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    Electromagnetic heating of Io (1980)
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    Publication Date: 2011-08-18
    Description: The electromagnetic heating of the Io interior is considered as an alternative to tidal dissipation to account for the observed volcanic activity. The characteristics of the time-varying magnetic field of Jupiter as seen from Io are discussed, and the range of possible rock conductivities is examined. Interior heating due to the transverse electric and transverse magnetic modes is calculated. It is found that the TM mode appears to be insignificant as a heating source due to the high conductivity of the ionosphere, even when TM heating is concentrated in local hot regions. The TE mode is a more promising source of heating, although electromagnetic heating by either mode does not appear significant in comparison with other heat sources at present.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 10
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  • 52
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    History of the mass of Mercury (1980)
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    Publication Date: 2011-08-18
    Description: This paper discusses the calculation of the masses of planets, as a means to construct reliable tables for their positions. Emphasis is placed on the four inner planets and the moon, with additional consideration given to the history of the masses of Jupiter and Saturn. A smooth curve can be drawn with the logarithm of the masses of the earth, Venus, Mars, and the moon, but the point for Mercury lies substantially off the curve. An investigation of the material content, surface examination, and planet radius for the planets leads to a reexamination of the history of the value for the mass of Mercury.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Royal Astronomical Society; vol. 21
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  • 53
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    Possible determination of the deceleration parameter using lunar occultations and laser ranging observations (1980)
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    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 241
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  • 54
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    Carbonaceous chondrites. II - Carbonaceous chondrite phyllosilicates and light element geochemistry as indicators of parent body processes and surface conditions (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Petrographic analyses of CM matrices characterized four phyllosilicates in Murray and Murchison meteorites and Fe- and Mg-serpentines in Nogoya. All phyllosilicates and bulk matrices show enrichment of K relative to Na when compared with bulk meteorites; the loss of Na and some Cl, and the addition of H2O, CO2, and water-soluble organics during alteration indicates a partially open system. Synthesis of soluble organic materials may have occurred in CM matrices before aqueous alteration of the precursive phases. Nogoya was 95% altered and has a bulk C content of 5.2%, higher than any meteorite; also, it has the lowest measured C-13/C-12 ratio of any carbonaceous chondrite except for Karoonda.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 44; Oct. 198
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  • 55
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    On the relationship between secular brightness changes of Titan and solar variability (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Titan's geometric albedo varied noticeably from 1972 to 1978, in phase with variations in solar activity (Lockwood and Thompson, 1979). A series of radiative transfer and aerosol formation calculations were made to demonstrate the feasibility of the following scenario for these secular brightness changes. Solar activity changes, especially in the UV output of the sun, result in alterations to the mass production rate of aerosols in Titan's atmosphere, which lead to modifications of their microphysical properties. The latter, in turn, cause the albedo to vary. Current estimates of the change in the solar UV radiation below the dissociation limit of methane imply alterations to the mean radius of the aerosols over an 11-yr solar cycle that are consistent in sign and magnitude with those required to explain the observed secular brightness changes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Oct. 198
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  • 56
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    Properties of the Io plasma torus inferred from Voyager EUV data (1980)
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    Publication Date: 2011-08-17
    Description: A physical model for the Io plasma torus is constructed to explain the EUV radiative emission observed by the Voyager UV spectrometer. Electron impact excitation rate coefficients for electronic transitions of S III, S IV, O II and O III are calculated by the method of distorted waves (Davis, Kepple, and Blaha, 1976); these coefficients account for the asymmetric shape of the 686 A feature. It is concluded that the electron gas must have a distribution function with a non-Maxwellian tail. An approximate representation of the distribution function as two temperature components requires a cold component of 3.5-4 eV and density of 2000 per cu cm and a hot component of about 100 eV and density of 50-100 per cu cm to satisfy observational constraints.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 238
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  • 57
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    Cometary collisions on the moon and Mercury (1980)
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    Publication Date: 2011-08-17
    Description: Unusual swirl patterns of bright and dark material on the moon and Mercury are proposed to be remnants of collisions with gas/dust-rich regions within a cometary coma. This interpretation provides important new clues for understanding cometary fine structure, impact effects of low-density material, and the origin of certain pronounced magnetic anomalies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 284; Mar. 6
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  • 58
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    Atomic nitrogen in the upper atmosphere of Venus (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Atomic nitrogen has been detected in the upper atmosphere of Venus by the Pioneer-Venus Orbiter Neutral Mass Spectrometer (ONMS). Surface recombination of atomic nitrogen with atomic oxygen to form nitric oxide in the ion source allows it to be detected at mass 30. The scale height temperature of the mass 30 peak agrees with the scale height temperatures of the other species if it is assumed to be derived from atomic nitrogen. The diurnal variation of atomic nitrogen is approximately proportional to that of atomic oxygen with an estimated N/O ratio of 1.5% at 150 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Jan. 198
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    Measurements of wind vectors, eddy momentum transports, and energy conversions in Jupiter's atmosphere from Voyager 1 images (1980)
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    Publication Date: 2011-08-17
    Description: Voyager 1 narrow-angle images were used to obtain displacements of features down to 100 to 200 km in size over intervals of 10 hours. A global map of velocity vectors and longitudinally averaged zonal wind vectors as functions of the latitude, is presented and discussed
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Jan. 198
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  • 60
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    Martian isotopic ratios and upper limits for possible minor constituents as derived from Mariner 9 infrared spectrometer data (1977)
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 32; Sept
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  • 61
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    Impulsive penetration of filamentary plasma elements into the magnetospheres of the earth and Jupiter (1977)
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    Publication Date: 2011-08-17
    Description: Assuming that the solar wind plasma is usually nonuniform over distances of 10,000 km or less, it is shown that filamentary plasma elements stretched out from the sun can penetrate impulsively and become engulfed into the magnetosphere. The diamagnetic effects associated with these plasma inhomogeneities are observed in outer magnetospheres and magnetosheaths as dips or directional discontinuities in the magnetic field measurements. From the mean penetration distances of these diamagnetic plasma elements one can deduce a mean deceleration time, as well as an approximate value of the integrated Pedersen conductivity in the polar cusp of the earth and Jupiter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science; 25; Sept
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  • 62
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    Distribution of molecular weight in glyceride polymerizates or aggregates of them after contact with lunar grains (1977)
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    Publication Date: 2011-08-17
    Description: An attempt is made to report on experiments in which a molecular-weight increase was determined in thin layers of triglyceride-containing glycerides after thin-layer contact for two years with lunar topsoil grains at 25 C without any thermal activation. It is noted that solidification was observed on both dielectric grains and metal-rich areas and that changes in viscosity and molecular weights were first detected by solidification of surface layers. Gel permeation chromatography is described which detected a general shift of the Gaussian distribution of the molecular-weight data toward generally higher molecular weights as well as an increase in mean molecular weight. Reaction mechanisms are considered, and results of spectrographic analysis are cited which support the interpretations of the molecular-weight data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 16; May 1977
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  • 63
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    Possible Jovian methane emission at 76 GHz in coincidence with decameter activity (1977)
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    Publication Date: 2011-08-17
    Description: The tentative detection of a methane line in emission at 76.2 GHz in the atmosphere of Jupiter is reported. The observed feature is well-correlated with the presence and absence of Jovian decameter-emission activity on successive days. The present results may represent the first detection of extraterrestrial methane microwave emission.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 216
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    The clouds of Venus (1977)
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    Publication Date: 2011-08-17
    Description: The current state of knowledge of the Venusian clouds is reviewed. The visible clouds of Venus are shown to be quite similar to low level terrestrial hazes of strong anthropogenic influence. Possible nucleation and particle growth mechanisms are presented. The Pioneer Venus experiments that emphasize cloud measurements are described and their expected findings are discussed in detail. The results of these experiments should define the cloud particle composition, microphysics, thermal and radiative heat budget, rough dynamical features and horizontal and vertical variations in these and other parameters. This information should be sufficient to initialize cloud models which can be used to explain the cloud formation, decay, and particle life cycle.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 20; May 1977
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    The Pioneer Venus program (1977)
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    Publication Date: 2011-08-17
    Description: Mission timetables, spacecraft, scientific objectives, and payloads of the two mission, Orbiter and Multiprobe, planned for launch and encounter with Venus during the 1978 Venus mission opportunity are described. Basically, the Orbiter mission has the goal of global mapping of the clouds, atmosphere and ionosphere of Venus by remote sensing and radio occultation, global studies by in situ measurements of the upper atmosphere and ionosphere and solar wind-ionosphere interaction region, and determination of gravitational field harmonics from perturbations of the spacecraft orbit. The Multiprobe mission will study the nature and composition of the clouds, the structure of the atmosphere, the circulation pattern, and the characteristics of the planetary environmental interaction with the solar wind.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 20; May 1977
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    The exploration of Venus (1977)
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    Description: The paper outlines the evolution of the Pioneer Venus program from the initial meeting of a consortium of scientists to study the feasibility of a simple entry probe to Venus, through the Planetary Explorer missions, to the Orbiter Mission proposals. Major recommendations of the 1970 National Academy of Sciences study on Venus exploration planning and of the 1972 Pioneer Venus Science Steering Group report are mentioned.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 20; May 1977
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    Composition and structure of the atmosphere of Venus (1977)
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    Publication Date: 2011-08-17
    Description: Some of the main questions regarding the composition, structure, and origin of the atmosphere of Venus are posed. These questions are (1) the distribution of the constituents of the lower atmosphere, (2) cloud composition, (3) the planet's surface and interior as revealed by atmospheric data, (4) the state property profiles and their variation over the planet, (5) the reason for the high temperatures of the lower atmosphere, (6) composition and temperature profiles of the upper atmosphere and location of the homopause, (7) spatial and temporal variations in the upper atmosphere, (8) the cause of the stability of CO2 - global circulation or local turbulence, (9) influence of neutral composition on the thermal structure, (10) response of upper atmosphere to change in solar EUV and solar wind, (11) the source and destination of the atmosphere, and (12) the location of Venus's water. The main parameters to be measured which will aid in resolving these problems are enumerated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 20; May 1977
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  • 68
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    The surface and interior of Venus (1977)
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    Publication Date: 2011-08-17
    Description: The present knowledge of Venus is reviewed with discussions of the nature and history of both the surface, crust and interior. Instrumentation on board the Pioneer Venus Orbiter, including the radar mapper, radio tracking and the fluxgate magnetometer, is described. Topographic, geological, Bouguer gravity, magnetic, and crustal thickness maps will be constructed from Orbiter data. These maps should provide information on composition and thermal history, the major geological or geophysical provinces, the rate of past and present tectonic activity, and evidence of past or present MHD dynamos.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 20; June 197
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    The Venus ionosphere and solar wind interaction (1977)
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    Publication Date: 2011-08-17
    Description: The current state of knowledge of the chemistry, dynamics and energetics of the upper atmosphere and ionosphere of Venus is reviewed together with the nature of the solar wind-Venus interaction. Because of the weak, though perhaps not negligible, intrinsic magnetic field of Venus, the mutual effects between these regions are probably strong and unique in the solar system. The ability of the Pioneer Venus Bus and Orbiter experiments to provide the required data to answer the questions outstanding is discussed in detail.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 20; June 197
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    The thermal balance of the atmosphere of Venus (1977)
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    Publication Date: 2011-08-17
    Description: Current knowledge of the temperature structure of the atmosphere of Venus is briefly summarized. The principal features to be explained are the high surface temperature, the small horizontal temperature contrasts near the cloud tops in the presence of strong apparent motions, and the low value of the exospheric temperature. In order to understand the role of radiative and dynamical processes in maintaining the thermal balance of the atmosphere, a great deal of additional data on the global temperature structure, solar and thermal radiation fields, structure and optical properties of the clouds, and circulation of the atmosphere are needed. The ability of the Pioneer Venus Orbiter and Multiprobe Missions to provide these data is indicated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 20; June 197
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  • 71
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    Dynamics, winds, circulation and turbulence in the atmosphere of Venus (1977)
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    Publication Date: 2011-08-17
    Description: With the possible exception of the lowest one or two scale heights, the dominant mode of circulation of Venus' atmosphere is a rapid, zonal, retrograde motion. Global albedo variations in the ultraviolet may reflect planetary scale waves propagating relative to the zonal winds. Other special phenomena such as cellular convection in the subsolar region and internal gravity waves generated in the interaction of the zonal circulation with the subsolar disturbance may also be revealed in ultraviolet imagery of the atmosphere. We discuss the contributions of experiments on the Orbiter and Entry Probes of Pioneer Venus toward unravelling the mystery of the planet's global circulation and the role played by waves, instabilities and convection therein
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 20; June 197
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  • 72
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    The ionospheres of Saturn, Uranus, and Neptune (1977)
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    Publication Date: 2011-08-17
    Description: Models of the ionospheres of Saturn, Uranus, and Neptune are presented. It is postulated that galactic cosmic-ray ionization is an important component of these ionospheres. For example, in the case of Neptune, the level of ionization caused by cosmic rays is comparable with that due to solar extreme-ultraviolet (EUV) radiation. The existence of cosmic-ray, as well as solar EUV-produced ionization, could be a valuable diagnostic tool for investigating the atmospheric thermal structure of those planets.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 215
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  • 73
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    Lunar transient phenomena /LTP/ - Manifestations, site distribution, correlations and possible causes (1977)
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    Publication Date: 2011-08-17
    Description: More than 1400 observations of lunar transient phenomena (LTP), encompassing brightenings, darkenings, and gaseous, reddish, and bluish events, are analyzed in an attempt to determine the possible causes of LTP. Hypotheses considered include effects of earth tides on the moon, low-angle illumination, thermal luminescence, UV heating, solar-particle acceleration by the magnetopause of earth's magnetotail, terrestrial magnetotail bow-shock-front turbulence, cathode luminescence due to magnetotail effects, and solar-flare particle bombardment. Analysis are performed in terms of histograms of the number of observations vs. phase of anomalistic period and of number vs. moon's age, percentage of numbers of observed phenomena and percentage of expected numbers as well as their ratios, and albedo behavior over a lunation period of chosen permanent points in ten specific features. The results indicate that different phenomena may have different causes, strong tidal effects are dubious, correlations with sunrise are most frequent, and the distribution of all LTP sites is distinct from that of deep- and shallow-focus moonquake epicenters.
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    Minor planets and related objects. XXIII - Photometry of asteroid /7/ Iris (1977)
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    Publication Date: 2011-08-17
    Description: Analysis of light curves and UBV photometry yields a model for (7) Iris as an ellipsoid with axial ratios 3:4:5. The North Pole orientation is near 41 deg ecliptic latitude and 11 deg longitude.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal; 82; June 197
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    Picture of Ganymede (1977)
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    Publication Date: 2011-08-17
    Description: Spin-scan images of Ganymede obtained by the imaging photopolarimeter of Pioneer 10 in December 1973 are described and presented. Intensity measurements in the blue and red scans are provided. The width of the scan elements is 0.5 mrad which is the size of the aperture in the focal plane of the telescope; the height is also 0.5 mrad (1 millisec integration - or dwell-time at 5 rpm spin rate). The distance of Pioneer 10 from Ganymede was 7.8 x 10 to the fifth km, and the resolution is therefore 390 km. The spin-scan image is in general agreement with Lyot's visual observations (Dollfus, 1961). Preliminary results on polarimetry of Ganymede obtained during the flyby of Pioneer 10 are discussed with attention to the question of whether water frost, NaCl powdered crystals, or other substances is responsible for the observed pattern.
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    Phobos and Deimos (1977)
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    Publication Date: 2011-08-17
    Description: Ground-based and spacecraft observations of Phobos and Deimos are reviewed and the satellites' origin is discussed. The crater densities of both bodies are close to the saturation level. The largest impact events may have caused extensive fracturing of their surfaces. The surfaces are at least 1.5 billion years old and may date back to the early history of the solar system. The Martian satellites display large deviations from sphericity. As a result of tidal processes, they are in synchronous rotation. Several independent lines of evidence show that they have regoliths. Despite some provocative arguments, their internal strengths and the nature of their interior are poorly known at present. Photometric measurements suggest that they are made of either carbonaceous chondritic material or a basalt. Sinclair (1972), Born and Duxbury (1975) and Shor (1975) apparently have successfully determined Phobos' secular acceleration. Their value of approximately .001 deg/year/year implies that the interior of Mars has a low specific dissipation factor (about 100), may indicate that a portion of the Martian interior is experiencing partial melting. The low inclination of the satellites' orbits indicates that they were formed as part of the same process that resulted in Mars.
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    Surface properties of a north ray crater soil /Apollo 16/ (1977)
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    Publication Date: 2011-08-17
    Description: Surface properties of lunar fines sample 67481 have been investigated by measuring the adsorptions of nitrogen (at -196 C) and water (at 20 C). Characteristics of this sample are similar to those of samples from other locations on the lunar surface and include the more typical alteration reaction with adsorbed water. Although their maturities are markedly different, the surface properties of 67481 are very much like those of the more mature 63341 from the adjacent station 13. These results indicate that the surface properties of lunar soils attain an equilibrium state faster than other properties used to indicate maturity.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 35; 1, Ma; May 1977
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    Solar radiation incident on Mars and the outer planets - Latitudinal, seasonal, and atmospheric effects (1977)
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    Publication Date: 2011-08-17
    Description: Calculations of the daily solar radiation incident at the tops of the atmospheres of Mars and the outer planets and its variability with latitude and season are presented in a series of figures and tables. The changes in the latitudinal and seasonal distributions of daily surface insolation during the great Martian dust storm of 1971 (when Martian atmospheric optical depth increased from about tau = 0.1 to 2.0) were significant and dramatically illustrate the effect of atmospheric aerosols on surface insolation; i.e., the mean annual daily insolation at the poles decreased by more than a factor of 100 as tau increased from 0.1 to 2.0.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 31; May 1977
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    The deficiency of siderophile elements in the moon (1977)
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    Description: An attempt is made to reconcile a plausible origin of the moon with the observed deficiency of siderophile elements in the moon. A numerical analysis is performed which indicates that at least 1% metal was needed to extract nickel successfully from the moon and that the deficiency of lunar siderophiles can be explained on the basis of a fission hypothesis. It is suggested that leaching by liquid metallic iron caused the lunar deficiency and that the leaching took place in the protoearth from which the moon subsequently formed by fission.
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    Distribution and flux of micrometeoroids (1977)
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    Publication Date: 2011-08-17
    Description: The mass distribution, flux, and distribution in space of the micrometeoroid complex at 1 AU are estimated on the basis of data from Apollo 17 rocks and recent calibrations of solar-flare track-production rates. It is found that the size frequency distribution of microcraters on lunar rocks suggests a bimodal mass distribution of micrometeoroids, but the precise form of the curve requires further definition, particularly insofar as the degree of depletion of particles producing craters 10 to 100 microns in diameter is concerned. Variations in slope with crater-diameter or particle-mass increments are shown to indicate that different processes affect one or more particle populations. Fluxes corresponding to varied lunar surface orientation and residence time are calculated, but no striking difference is observed between the flux of submicron-diameter particles with orbits in the plane of the ecliptic and fluxes of particles with orbits normal to the plane in the solar apex direction.
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    A calculation of Saturn's gravitational contraction history (1977)
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    Description: A gravitational-contraction history is calculated for a homogeneous quasi-equilibrium Saturn model of solar composition without a rock-ice core and without allowance for the possible separation of hydrogen and helium. The calculations begin at the time when Saturn's radius was ten times its current value, and the subsequent gravitational contraction is followed for 4.5 billion years. The results obtained are given in terms of the path of the evolving model on the H-R diagram, the variation of central temperature with central density, the time variation of radius and internal luminosity, and the energy changes that take place during the evolution. These results are compared with those of similar calculations for Jupiter, and the internal structure of the evolutionary models is examined in detail. The Saturn calculations yield a radius at the current epoch that is 9% larger than the observed value and an excess luminosity comparable to that observed. It is noted that an inhomogeneous model containing a solar-mix envelope and a central rocky core has a radius equal to the observed value.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 30; Jan. 197
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    The Apollo 17 'melt sheet' - Chemistry, age and Rb/Sr systematics (1977)
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    Publication Date: 2011-08-17
    Description: Major, minor, and trace-element compositions, age data, and Rb/Sr systematics of Apollo 17 boulders have been compiled, and additional analyses performed on a norite breccia clast (77215) included in the Apollo 17, Station 7 boulder. The Apollo 17 boulders are found to be identical or nearly so in major, minor, and trace-element composition, suggesting that they all originated as an impact melt analogous to melt sheets found in larger terrestrial craters. The matrix dates (Ar-40/Ar-39) and Rb/Sr systematics available suggest that this impact melt formed by a single impact about 4 billion years ago. This impact excavated, shocked, brecciated, and melted norites, norite cumulates, and possibly anorthositic gabbros and dunites about 4.4 billion years old. The impact was likely a major one, possibly the Serenitatis basin-forming event.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 33; 3, Ja; Jan. 197
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    Preliminary findings of the Viking gas exchange experiment and a model for Martian surface chemistry (1977)
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    Publication Date: 2011-08-17
    Description: Earlier results reported from the Viking Lander-1 experiment are reexamined and interpreted in terms of a model of the Martian soil surface morphology and chemistry. Major events in the gas exchange experiment (GEX) first cycle are tabulated and data are presented on the sample processing and transport environments experienced by the soil samples. Oxygen and CO2 evolved from humidified Martian soil in GEX and slight changes in N2 present are investigated. A soil model involving iron oxide coating on silicate material is entertained to yield a mechanistic explanation of the experimental findings, and invocation of biotic processes is eschewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 265; Jan. 13
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    Asteroid families - Observational evidence for common origins (1977)
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    Description: Colors of minor planets in the UBV system indicate compositions quite distinct from those of the field population in each of three Hirayama families. The Eos and Koronis families apparently originated from the collisional fragmentation of undifferentiated silicate bodies, and the Nysa group from a geochemically differentiated parent body
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 197; July 15
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    Formation of the outer planets and satellites (1977)
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    Description: A mechanism for the formation of the outer planets is proposed, the basis of which is the idea that the giant planets contain an excess of chemically condensable materials over solar composition. Planetary cores were formed by the clumping together of chemically condensed bodies forming a thin disk in the solar nebula. Gas surrounding a core becomes unstable against collapse onto the core. In the case of Jupiter and Saturn, much of the collapsing gas goes into orbit about the formed planet, forming a relatively thin circumplanetary disks with differential rotation in the prograde sense. For Uranus and Neptune, the dynamical collapse mechanism is unlikely. A disk of gas around Uranus may have been formed during a collision of the protoplanet with a large body. The circumplanetary disks then form the basis for formation of satellite systems, in which the Goldreich-Ward instability mechanism plays a role.
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    Saturn's rings - A new survey (1977)
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    Description: Observations of radar returns from Saturn's rings, together with radio interferometry of their absorption of radiation from the disk, combine to require an effective radius of ring particles of about 6 cm or larger. It is suggested that the ring particles may also include, in addition to the known ice constituent, a mixture of the clathrated hydrate of methane and ammonia hydrate. A two-density model for ring particles is possible in which a matrix of low density contains many nodules of higher-density ice particles; in this case, radii nearly as large as the observed ring thickness would be possible. Improved resolution in radio observations at 21 cm or, if necessary, at longer wavelengths for narrow ring openings is perhaps the most useful method for determining upper limits on the particle size.
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    Relative crater production rates on planets (1977)
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    Description: The relative numbers of impacts on different planets, estimated from the dynamical histories of planetesimals in specified orbits (Wetherill, 1975), are converted by a described procedure to crater production rates. Conversions are dependent on impact velocity and surface gravity. Crater retention ages can then be derived from the ratio of the crater density to the crater production rate. The data indicate that the terrestrial planets have crater production rates within a factor ten of each other. As an example, for the case of Mars, least-squares fits to crater-count data suggest an average age of 0.3 to 3 billion years for two types of channels. The age of Olympus Mons is discussed, and the effect of Tharsis volcanism on channel formation is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 31; June 197
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    Detection of rings around Uranus (1977)
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    Description: A description is presented of partial occultations of SAO 158687 by a series of rings around the planet Uranus. A 61-cm telescope at Perth Observatory in Western Australia was used in the investigations. Measurements were made using a conventional single-channel photometer equipped with an RCA C31034B photomultiplier. Uranus was centered in a 28-arc sec diameter aperture during the observations. An occultation of SAO 158687 by Uranus itself did not occur at Perth. However, five brief partial occultations of SAO 158687 were detected with the chart recorder. The midtimes, durations, and depths of these events are listed in a table.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 267; May 26
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  • 89
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    Lunar magnetic permeability studies and magnetometer sensitivity (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A regression of quiet magnetic field components simultaneously measured by the two Explorer 35 magnetometers reveals uncertainties in effective sensitivity factors of up to a few percent in one or both of these instruments. Given this, the validity of previous lunar permeability studies based on Explorer 35/ALSEP regressions, wherein inferences are drawn from regression line slopes differing from unity by the order of one percent, is called into question. We emphasize the need to critically address the question of small deviations in magnetometer sensitivity factors from nominal values as a part of any two-magnetometer lunar permeability study.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 4; Apr. 197
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  • 90
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    An improved value of the lunar moment of inertia (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The lunar gravitational research reported on by Gapcynski et al., (1975) has been extended to include an additional 600 days of the time variation of ascending node for the Explorer 49 spacecraft. Analysis of these additional data resulted in an improved value of the second-degree zonal harmonic coefficient C(20) = (-2.0219 equal to 0.0091) times 10 to the minus 4. This value of C(20) used in conjunction with the parameters beta equal to libration (631.27 + or - 0.03) times 10 to the minus 6 and gamma to (227.7 + or - 0.7) times 10 to the minus 6 yields a more accurate definition of the lunar moment of inertia ratio equal to 0.391 + or - 0.002.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Apr. 10
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  • 91
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    Yes, Kakangari is a unique chondrite (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The position of the Kakangari chondrite as the representative of a new class of chondrites is considered, taking into account the results of the analysis of a 17.1-mg piece of Kakangari for 20 elements. Elemental concentration data are compared for Kakangari and other meteorite groups. Data for the most similar groups, C2, C3(V), L, and E4 chondrites are represented in a graph along with Kakangari data. It is found that pronounced differences exist between Kakangari and the other meteorite classes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 265; Jan. 20
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  • 92
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    Lunar Rb-Sr chronology (1977)
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    Publication Date: 2011-08-17
    Description: It has been established with the aid of Rb-Sr studies that lunar chronology consists of five episodes, including the formation of the moon approximately 4.6 AE ago (1 AE = 1000 million years), a period of intense bombardment by planetary debris resulting in the formation of the major lunar basins, the end of this period at 3.9-4.0 AE ago, a period of mare flooding extending from 3.9 to 3.2 AE ago, and a relatively quiescent period from 3.2 AE ago to the present. In addition, Rb-Sr-studies have provided valuable constraints on the geochemical evolution of the moon through the determination of the initial Sr-87/Sr-86 ratios which limit the Rb/Sr ratios of the source materials for lunar rocks. Attention is given to the characteristics of the Rb-Sr method, the analytical techniques, the ages of lunar mare basalts, the non-mare rocks, the studies conducted in connection with the various Apollo missions, the lunar cataclysm, lunar soils, and aspects of crustal contamination.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Physics and Chemistry of the Earth; 10; 2, 19; 1977
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  • 93
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    Volatile elements, carbon, nitrogen, sulfur, sodium, potassium and rubidium in the lunar regolith (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Physics and Chemistry of the Earth; 10; 1, 19; 1977
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  • 94
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    Structure of the atmosphere of Mars in summer at mid-latitudes (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Instruments onboard Viking 1 and 2 landers were used to measure the structure of Mars' atmosphere in situ from near the surface to an altitude of 120 km. Atmospheric structure was found to be well defined by the instruments and relatively similar at the two sites. Viking 1 and 2 surface pressures were 7.62 and 7.81 mbar, and temperatures were 238 K and 236 K, respectively, with pressures at the elevation of the reference ellipsoid of 6.74 and 6.30 mbar. Mean temperature was found to decrease with a lapse rate of about 1.6 K/km (significantly subadiabatic) from above the boundary layer to about 40 km. The temperature was then near isothermal with a large-amplitude wave superimposed (attributed to the diurnal thermal tide). It is suggested that the mean profile is governed by radiative equilibrium. The obtained density data are found to merge well with those obtained by an upper-atmosphere spectrometer (at 200 km). The temperature wave is found to continue above 100 km while increasing in wavelength and amplitude.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Sept. 30
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  • 95
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    Search for color changes and brightening of Io upon eclipse reappearance (1977)
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    Publication Date: 2011-08-17
    Description: Medium-resolution spectra were made of Io as it emerged from two eclipses in December 1975. In the wavelength range 4000-5800 A, no spectral changes greater than the standard deviations were observed when the spectrum of Io just after reappearance was divided by the spectrum of Io 20 min later. No substantial increase in total brightness was observed over the same time interval. These observations were made at a time when the sub-earth point was in Io's northern hemisphere; therefore, prediction of positive posteclipse brightening in this circumstance is not confirmed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 32; Oct. 197
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  • 96
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    Mariner 9 Ultraviolet Spectrometer Experiment: Mars Atomic Oxygen 1304-A Emission (1977)
    In:  CASI
    Details
    Publication Date: 2011-06-29
    Description: Selected results are presented for an analysis of Mariner 9 1304-A data from the first 100 passes. Based on a comparison of limb data, the exospheric temperature appears lower on several Mariner 9 passes than when Mariner 6 and 7 encountered the planet in 1969. Temperatures of 300 and 350 K are considered in the atmospheric modeling. At 300 K, derived values of the atomic oxygen concentration are typically between 0.5 and 1 percent of the total density at 135 km, based on fitting theoretical intensities to limb data from several passes. Structure in the limb data below 200 km suggests the possibility that approximately 0.2 kR of the observed approximately 0.8 kR near 150 km is due to dissociative excitation of CO2. There is variability in limb profiles indicating changes in the O distribution with time. The variability does not appear to follow a recognizable pattern. Interpretation of the 1304-A disc data shows a correlation in intensity with the 10.7 cm solar flux and larger O concentrations in the afternoon than in the morning. The correlation in intensity with the 10.7 cm flux is probably due largely to variation in the solar 1304-A fluxes. Selected disc data show localized and random enhancements in the intensity.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 97
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    Viking Radio Occultation Measurements of the Martian Atmosphere and Topography: Primary Mission Coverage (1977)
    In:  Other Sources
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    Publication Date: 2016-11-16
    Description: Radio occultation measurements were made at approximately 50 locations on Mars with the Viking Orbiter 1 S (2.3 GHz) and X (8.4 GHz) band tracking links during October 1976. The measurements have been used to study the topography and atmosphere of Mars at latitudes ranging from about 75 deg S to 70 deg N. By using the ingress and egress times obtained from the observed limb diffraction effects together with the best ephemerides available for the orbiter and the planet we have determined the surface elevations at the occultation points relative to the reference areoid. The observations agree with Mariner 9 and radar data to within 2 km. The mean atmospheric pressure at the areoid level was found to be 5.9 mbar during the northern midsummer season, a value which agrees quite well with data obtained at the landing sites. By comparing the new electron density measurements with earlier Mariner data we have determined that the temperature and the plasma scale height of the upper atmosphere appear to be functions of solar activity.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; Volume 82; No. 28; 4317-4324
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  • 98
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    Some Martian Volcanic Features as Viewed from the Viking Orbiters (1977)
    In:  Other Sources
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    Publication Date: 2016-11-16
    Description: A summary is presented of the results of some new observations on Martian volcanic features made from the Viking orbiters. Most of these observations are concerned with the Tharsis and Alba regions. The youth, size, and style of the volcanic features in these areas render them particularly susceptible to analysis. Excellent coverage was also acquired of Apollinaris Patera. It has many features of the Tharsis shields, with a cliff around its circumference and a large central caldera. Olympus Mons and its vicinity are examined, taking into account the shield of Olympus Mons, mass movement features along the basal scarp, the basal plains, the relative ages of Olympus Mons and the basal plains, and grooved terrain.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; Volume 82; No. 28; 3985–4015
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  • 99
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    Mars Gravity Field: Combined Viking and Mariner 9 Results (1977)
    In:  Other Sources
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    Publication Date: 2016-11-16
    Description: A Martian gravity field of sixth degree and order has been determined from an analysis of a combination of Viking and Mariner 9 spacecraft Doppler tracking data. A short-arc technique utilizing approximately 4 hours of data centered at periapsis was used, and the data covered 16 arcs from Mariner 9 and 17 arcs from the Viking orbiters. The data were selected so as to obtain a uniform distribution of periapsis longitudes over the surface of Mars, and both S band and X band data were used where possible to eliminate charged particle effects. Inclusion of the Viking data arcs altered the Martian geoid features, as defined by previous short-arc analysis techniques of Mariner 9 data, by about 80 m in the southern hemisphere and about 140 m in the northern hemisphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; Volume 82; No. 28; 4325-4327
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  • 100
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    Geological Observations in the Cydonia Region of Mars from Viking (1977)
    In:  Other Sources
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    Publication Date: 2016-11-16
    Description: During the Viking mission, three broad areas of the northern plains were investigated as possible landing sites for Viking lander 2. We present a geological map of the area designated the B1 landing site in Cydonia centered on 45 deg N latitude, 4 deg W longitude. Viking imagery of this area has given detailed coverage, allowing the northern plains to be examined in more detail over wider areas than was possible from Mariner 9. Some plains areas with polygonal fracture patterns are considered to be pediments in ancient southern hemisphere rocks. The fracture patterns predate at least some of the younger northern plains material. Several northern plains units are distinguished as well as surface textures of unknown origin. Viking pictures provide good data for future studies of stratigraphy and surface process in this region and others like it in northern latitudes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; Volume 82; No. 28; 4111-4120
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