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  • LUNAR AND PLANETARY EXPLORATION  (105)
  • Lunar and Planetary Science and Exploration  (50)
  • ASTROPHYSICS  (2)
  • SPACE SCIENCES (GENERAL)  (2)
  • 1
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    Gusev Crater Paleolake: Two-Billion Years of Martian Geologic, (and Biologic?) History (1998)
    In:  CASI
    Details
    Publikationsdatum: 2004-12-03
    Beschreibung: Ancient Martian lakes are sites where the climatological, chemical, and possibly biological history of the planet has been recorded. Their potential to keep this global information in their sedimentary deposits, potential only shared with the polar layered-deposits, designates them as the most promising targets for the ongoing exploration of Mars in terms of science return and global knowledge about Mars evolution. Many of the science priority objectives of the Surveyor Program can be met by exploring ancient Martian lake beds. Among martian paleolakes, lakes in impact craters represent probably the most favorable sites to explore. Though highly destructive events when they occur, impacts may have provided in time a significant energy source for life, by generating heat, and at the contact of water and/or ice, deep hydrothermal systems, which are considered as favorable environments for life. In addition, impact crater lakes are changing environments, from thermally driven systems at the very first stage of their formation, to cold ice-protected potential oases in the more recent Martian geological times. Thus, they are plausible sites to study the progression of diverse microbiologic communities.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: Mars Surveyor 2001 Landing Site Workshop
    Format: text
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  • 2
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    Mars Aerobot Missions (2000)
    In:  CASI
    Details
    Publikationsdatum: 2004-12-03
    Beschreibung: Mars aerobots constitute a class of mission nearly a factor of 10 smaller than earlier concepts for Mars balloons. A key goal is to achieve high payload mass fraction in a small total systems mass and to maximize the scientific potential of that payload. The "low and slow" attributes of aerobot flight paths afford advantages for many observations and measurements of Mars. Scientific objectives include surveys of remnant magnetism, studies of the surface with high resolution stereo imaging, and investigations of the structure and dynamics of the atmosphere with an in situ meteorology payload.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: Concepts and Approaches for Mars Exploration; Part 1; 131; LPI-Contrib-1062
    Format: text
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  • 3
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    Geology of the Icy Galilean Satellites: Understanding Crustal Processes and Geologic Histories Through the JIMO Mission (2003)
    In:  CASI
    Details
    Publikationsdatum: 2004-10-30
    Beschreibung: Knowledge of the geology, style and time history of crustal processes on the icy Galilean satellites is necessary to understanding how these bodies formed and evolved. Data from the Galileo mission have provided a basis for detailed geologic and geo- physical analysis. Due to constrained downlink, Galileo Solid State Imaging (SSI) data consisted of global coverage at a -1 km/pixel ground sampling and representative, widely spaced regional maps at -200 m/pixel. These two data sets provide a general means to extrapolate units identified at higher resolution to lower resolution data. A sampling of key sites at much higher resolution (10s of m/pixel) allows evaluation of processes on local scales. We are currently producing the first global geological map of Europa using Galileo global and regional-scale data. This work is demonstrating the necessity and utility of planet-wide contiguous image coverage at global, regional, and local scales.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: Forum on Concepts and Approaches for Jupiter Icy Moons Orbiter; 23; LPI-Contrib-1163
    Format: text
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  • 4
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    Wind abrasion on Venus: A means for experimental investigations (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-06
    Beschreibung: A study to determine the feasibility of conducting experiments to simulate the aeolian environment on Venus as related to wind abrasion was completed. Ideally, such experiments should involve complete investigation of weathering, in which mechanical, thermal, and chemical parameters are taken into account. This is particularly important for Venus, where atmospheric temperatures and pressures at the surface produce an environment which is equivalent to low or medium grade metamorphic conditions on Earth. Details that describe the Venus Aeolian Abrasion Device (VAAD) are included. The VAAD device would enable experiments to be conducted with the same chemistry, temperature, pressure, and other physical properties of the Venus atmosphere near the surface. The proposed device enables the important aeolian parameters to be controlled and monitored, including particle size, velocity, impact-angle and flux, atmospheric pressure, temperature, and gas composition.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA. Washington Repts. of Planetary Geol. Program; p 67-68
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  • 5
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    Morphology of fresh craters on Ganymede and the origin of pedestal craters (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-06
    Beschreibung: Properties of the planetary surface and subsurface can affect the morphology of impact craters. A mechanism was proposed to explain pedestal craters and domed floors within fresh craters on Ganymede. Voyager 1 and 2 images with resolutions = to or 3.2 km/lp were examined and 523 fresh craters were identified. For each crater, the rim and ejecta diameters were measured, and the crater was characterized by ejecta class(es), interior features, floor morphology and target terrain. Of the craters examined, 97 show moderate to prominent doming of the crater floor; 340 craters have continuous ejecta which terminates in a scarp pedestal craters, of which 86 (25%) have a high albedo diffuse deposit beyond the pedestal.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 94-96
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  • 6
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    Velocities of windblown particles in saltation: Venus, Earth, and Mars (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-06
    Beschreibung: Particle velocities were determined in environmental wind tunnels capable of simulating aeolian processes on Earth, Mars, and Venus. Comparisons of results for Earth, Mars, and Venus reveal some remarkable differences. Most particles achieve speeds nearly equal to freestream wind speed on Venus, but seldom achieve half the wind speed on Mars; Earth cases are of intermediate values. This is attributed to the differences in atmospheric density and to the threshold wind speeds among the three planetary environments. Particles are more easily moved in the dense venusian atmosphere than on Mars; consequently, threshold speeds are very low, and for the range of wind speeds in which most movement is presumed to occur (just above threshold speeds), the grains need not be moving very fast to achieve 100% of the wind speed. Conversely, particles on Mars must accelerate very rapidly to achieve the speed of the high winds required for threshold, and despite the fact that saltation path lengths are long on Mars, most grains fall to the surface before achieving even 50 to 60% of freestream wind speed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA. Washington Rept. of Planetary Geol. Programs; p 166-168
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  • 7
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    Aeolian processes on Venus (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-06
    Beschreibung: Many of the questions regarding aeolian processes on Venus and the subsequent implications for surface history involve understanding the physics of particle motion in the venusian environment. The surface environment of Venus is simulated as closely as practicable using the Venus Wind Tunnel and to determine threshold wind speeds, particle flux, particle velocities, and the characteristics of various aeolian bedforms. Despite the relatively low wind speeds on Venus, the flux of windblown material on Venus is potentially high. A high fraction of material is transported as surface creep by rolling, estimates yield rates up to 100 kg per cm lane width per year depending upon the availability of material and wind frequency, suggesting that the formation of lowland plains by aeolian processes and the burial of various landforms such as impact craters could occur on short geological time-scales. Wind tunnel simulations demonstrate that aeolian processes may be very effective in modifying the surface through erosion and deposited and may have an important influence on the composition of the atmosphere.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA. Washington Repts. of Planetary Geol. Program; p 69-70
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  • 8
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    Imaging of Venus from Galileo - Early results and camera performance (1992)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-24
    Beschreibung: Three images of Venus have been returned so far by the Galileo spacecraft following an encounter with the planet on UT February 10, 1990. The images, taken at effective wavelengths of 4200 and 9900 A, characterize the global motions and distribution of haze near the Venus cloud tops and, at the latter wavelength, deep within the main cloud. Previously undetected markings are clearly seen in the near-infrared image. The global distribution of these features, which have maximum contrasts of 3 percent, is different from that recorded at short wavelengths. In particular, the 'polar collar', which is omnipresent in short wavelength images, is absent at 9900 A. The maximum contrast in the features at 4200 A is about 20 percent. The optical performance of the camera is described and is judged to be nominal.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Advances in Space Research (ISSN 0273-1177); 12; 9, Se; 91-103
    Format: text
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  • 9
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    Estimated grain saltation in a Martian atmosphere (1976)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Mariner 9 spacecraft images showing evidence of variable surface features and surface erosion resulting from atmospheric wind on Mars have caused a renewed interest in the eolian mechanics of saltating grains. To study this phenomenon, both experimental investigation in an atmospheric wind tunnel and numerical solutions of the equations of motion of a single grain under Martian surface conditions were conducted. The numerical solutions for earth were used and empirically adjusted to correlate with existing experimental data for Mars. These modified equations were then solved to estimate grain motion for Mars. These calculations show the importance of a lifting force on the grain to initiate motion in both earth and Mars calculations. Major findings include a comparison of earth and Mars grain trajectories that show Mars length scales to be longer and to fall with a higher terminal grain velocity. The grains in the Mars calculation also made a smaller collision angle with the surface on rebound.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 81; Nov. 10
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  • 10
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    Wind tunnel studies of Martian aeolian processes (1974)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-16
    Beschreibung: In order to determine the nature of Martian aeolian processes, an investigation is in progress which involves wind tunnel simulations, geologic field studies, theoretical model studies, and analyses of Mariner 9 imagery; this report presents the preliminary results. Threshold speed experiments were conducted for particles ranging in relative density from 1.3 to 11.35 and diameter from 10.2 to 1290 microns to verify and better define Bagnold's (1941) expression for grain movement, particularly for low particle Reynolds numbers and to study the effects of aerodynamic lift and surface roughness. Wind tunnel simulations were conducted to determine the flow field over raised rim craters and associated zones of deposition and erosion.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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