Astrogeology Science Center

Publications

Filter Total Items: 890
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Year Published: 1992

Enhanced visualization for the interpretation of Magellan radar data: Supplement to the Magellan special issue

The differences of radar data from more familiar photographic images, coupled with the unique geologic characteristics of Venus's surface, can make interpretation of the standard Magellan data products difficult for both planetary scientists and nonspecialists. We describe a set of digital processing techniques for transforming individual remote‐...

Kirk, Randolph L.; Soderblom, Laurence A.; Lee, Ella M.

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Year Published: 1992

The geology and distribution of impact craters on Venus: What are they telling us?

Magellan has revealed an ensemble of impact craters on Venus that is unique in many important ways. We have compiled a data base describing the 842 craters on 89% of Venus' surface mapped through orbit 2578. (The craters range in diameter from 1.5 to 280 km.) We have studied the distribution, size‐density, morphology, geology, and associated...

Schaber, G.G.; Strom, R.G.; Moore, H.J.; Soderblom, Laurence A.; Kirk, Randolph L.; Chadwick, D.J.; Dawson, D.D.; Gaddis, L.R.; Boyce, J.M.; Russell, Joel F.

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Year Published: 1992

Lunar impact basins and crustal heterogeneity: New western limb and far side data from Galileo

Multispectral images of the lunar western limb and far side obtained from Galileo reveal the compositional nature of several prominent lunar features and provide new information on lunar evolution. The data reveal that the ejecta from the Orientale impact basin (900 kilometers in diameter) lying outside the Cordillera Mountains was excavated from...

Belton, Michael J.S.; Head, James W.; Carle m. Pieters; Greeley, Ronald; McEwen, Alfred S.; Neukum, G.; Klaasen, Kenneth P.; Anger, C.D.; Carr, M.H.; Chapman, C.R.; Davies, M.E.; Fanale, F. P.; Gierasch, P.J.; Greenberg, R.; Ingersoll, A.; Johnson, Torrence; Paczkowski, B.; Pilcher, C.B.; Veverka, J.

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Year Published: 1992

The canyon system on Mars

Individual Martian equatorial troughs are described, and their stratigraphy, geomorphology and structure are discussed. Possible origins and the overall sequence of events are addressed. Wall rock, interior layered deposits, irregular floor deposits, fractured floor material, and surficial deposits are examined. Chasma walls, wall stability, pits...

Lucchitta, Baerbel K.; McEwen, A.S.; Clow, Gary D.; Geissler, Paul E.; Singer, R.B.; Schultz, R.A.; Squyres, Steven W.

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Year Published: 1992

Lava-flow characterization at Pisgah Volcanic Field, California, with multiparameter imaging radar

Multi-incidence-angle (in the 25° to 55° range) radar data acquired by the NASA/JPL Airborne Synthetic Aperture Radar (AIRSAR) at three wavelengths simultaneously and displayed at three polarizations are examined for their utility in characterizing lava flows at Pisgah volcanic field, California. Pisgah lava flows were erupted in three phases;...

Gaddis, Lisa R.

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Year Published: 1990

Subsurface energy storage and transport for solar-powered geysers on Triton

The location of active geyser-like eruptions and related features close to the current subsolar latitude on Triton suggests a solar energy source for these phenomena. Solidstate greenhouse calculations have shown that sunlight can generate substantially elevated subsurface temperatures. A variety of models for the storage of solar energy in a sub-...

Kirk, Randolph L.; Brown, Robert H.; Soderblom, Laurence A.

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Year Published: 1990

Energy sources for triton's geyser-like plumes

Four geyser-like plumes were discovered near Triton's south pole in areas now in permanent sunlight. Because Triton's southern hemisphere is nearing a maximum summer solstice, insolation as a driver or a trigger for Triton's geyser-like plumes is an attractive hypothesis. Trapping of solar radiation in a translucent, low-conductivity surface layer...

Brown, R. H.; Kirk, Randolph L.; Johnson, T. V.; Soderblom, Laurence A.

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Year Published: 1990

Triton's geyser-like plumes: Discovery and basic characterization

At least four active geyser-like eruptions were discovered in Voyager 2 images of Triton, Neptune's large satellite. The two best documented eruptions occur as columns of dark material rising to an altitude of about 8 kilometers where dark clouds of material are left suspended to drift downwind over 100 kilometers. The radii of the rising columns...

Soderblom, Laurence A.; Kieffer, S.W.; Becker, T.L.; Brown, R. H.; Cook, A.F.; Hansen, C.J.; Johnson, T. V.; Kirk, Randolph L.; Shoemaker, E.M.

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Year Published: 1990

Volcanism in Northwest Ishtar Terra, Venus

Soviet Venera 15/16 radar images and topographic data for an area in NW Ishtar Terra, Venus (74°N, 313°E) contain evidence for the existence of a complex volcanic center. Located at the intersection of Akna and Freyja Montes (both elevated ∼4 to 7 km above the planetary reference radius of 6051 km), this volcanic center has a complex caldera...

Gaddis, Lisa R.; Greeley, Ronald

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Year Published: 1990

Dark materials in Valles Marineris: Indications of the style of volcanism and magmatism on Mars

Rifting on the equatorial canyon system of Valles Marineris provides a unique view of the interior of the Martian crust to depths reaching 7 km, exposing several in situ bedrock units which testify to past volcanic and magmatic processes on Mars. A thick, regionally extensive deposit observed in Coprates and Juventae chasmata is interpreted on the...

Geissler, Paul E.; Singer, Robert B.; Lucchitta, Baerbel K.

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Year Published: 1990

Flank tectonics of Martian volcanoes

On the flanks of Olympus Mons is a series of terraces, concentrically distributed around the caldera. Their morphology and location suggest that they could be thrust faults caused by compressional failure of the cone. In an attempt to understand the mechanism of faulting and the possible influences of the interior structure of Olympus Mons, we...

Thomas, Paul; Squyres, Steven W.; Carr, M.H.

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Year Published: 1990

Lava flow surface textures: SIR-B radar image texture, field observations, and terrain measurements

Space Shuttle Imaging Radar (SIR-8) images, field observations, and small-scale (cm) terrain measurements are used to study lava flow surface textures related to emplacement processes of a single hawaiian lava flow. Although smooth pahoehoe textures are poorly characterized on the SIR-B data, rougher pahoehoe types and the a'a flow portion show...

Gaddis, Lisa R.; Mouginis-Mark, Peter J.; Hayashi, Joan N.