37 results on '"Soderblom LA"'
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2. Close Cassini flybys of Saturn's ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus.
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Buratti BJ, Thomas PC, Roussos E, Howett C, Seiß M, Hendrix AR, Helfenstein P, Brown RH, Clark RN, Denk T, Filacchione G, Hoffmann H, Jones GH, Khawaja N, Kollmann P, Krupp N, Lunine J, Momary TW, Paranicas C, Postberg F, Sachse M, Spahn F, Spencer J, Srama R, Albin T, Baines KH, Ciarniello M, Economou T, Hsu HW, Kempf S, Krimigis SM, Mitchell D, Moragas-Klostermeyer G, Nicholson PD, Porco CC, Rosenberg H, Simolka J, and Soderblom LA
- Abstract
Saturn's main ring system is associated with a set of small moons that either are embedded within it or interact with the rings to alter their shape and composition. Five close flybys of the moons Pan, Daphnis, Atlas, Pandora, and Epimetheus were performed between December 2016 and April 2017 during the ring-grazing orbits of the Cassini mission. Data on the moons' morphology, structure, particle environment, and composition were returned, along with images in the ultraviolet and thermal infrared. We find that the optical properties of the moons' surfaces are determined by two competing processes: contamination by a red material formed in Saturn's main ring system and accretion of bright icy particles or water vapor from volcanic plumes originating on the moon Enceladus., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)
- Published
- 2019
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3. Diviner Lunar Radiometer observations of cold traps in the Moon's south polar region.
- Author
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Paige DA, Siegler MA, Zhang JA, Hayne PO, Foote EJ, Bennett KA, Vasavada AR, Greenhagen BT, Schofield JT, McCleese DJ, Foote MC, DeJong E, Bills BG, Hartford W, Murray BC, Allen CC, Snook K, Soderblom LA, Calcutt S, Taylor FW, Bowles NE, Bandfield JL, Elphic R, Ghent R, Glotch TD, Wyatt MB, and Lucey PG
- Subjects
- Cold Temperature, Extraterrestrial Environment, Ice, Radiometry, Spectrophotometry, Infrared, Moon
- Abstract
Diviner Lunar Radiometer Experiment surface-temperature maps reveal the existence of widespread surface and near-surface cryogenic regions that extend beyond the boundaries of persistent shadow. The Lunar Crater Observation and Sensing Satellite (LCROSS) struck one of the coldest of these regions, where subsurface temperatures are estimated to be 38 kelvin. Large areas of the lunar polar regions are currently cold enough to cold-trap water ice as well as a range of both more volatile and less volatile species. The diverse mixture of water and high-volatility compounds detected in the LCROSS ejecta plume is strong evidence for the impact delivery and cold-trapping of volatiles derived from primitive outer solar system bodies.
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- 2010
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4. The identification of liquid ethane in Titan's Ontario Lacus.
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Brown RH, Soderblom LA, Soderblom JM, Clark RN, Jaumann R, Barnes JW, Sotin C, Buratti B, Baines KH, and Nicholson PD
- Abstract
Titan was once thought to have global oceans of light hydrocarbons on its surface, but after 40 close flybys of Titan by the Cassini spacecraft, it has become clear that no such oceans exist. There are, however, features similar to terrestrial lakes and seas, and widespread evidence for fluvial erosion, presumably driven by precipitation of liquid methane from Titan's dense, nitrogen-dominated atmosphere. Here we report infrared spectroscopic data, obtained by the Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini spacecraft, that strongly indicate that ethane, probably in liquid solution with methane, nitrogen and other low-molecular-mass hydrocarbons, is contained within Titan's Ontario Lacus.
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- 2008
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5. Pyroclastic activity at Home Plate in Gusev Crater, Mars.
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Squyres SW, Aharonson O, Clark BC, Cohen BA, Crumpler L, de Souza PA, Farrand WH, Gellert R, Grant J, Grotzinger JP, Haldemann AF, Johnson JR, Klingelhöfer G, Lewis KW, Li R, McCoy T, McEwen AS, McSween HY, Ming DW, Moore JM, Morris RV, Parker TJ, Rice JW Jr, Ruff S, Schmidt M, Schröder C, Soderblom LA, and Yen A
- Abstract
Home Plate is a layered plateau in Gusev crater on Mars. It is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. A coarsegrained lower unit lies under a finer-grained upper unit. Textural observations indicate that the lower strata were emplaced in an explosive event, and geochemical considerations favor an explosive volcanic origin over an impact origin. The lower unit likely represents accumulation of pyroclastic materials, whereas the upper unit may represent eolian reworking of the same pyroclastic materials.
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- 2007
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6. The evolution of Titan's mid-latitude clouds.
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Griffith CA, Penteado P, Baines K, Drossart P, Barnes J, Bellucci G, Bibring J, Brown R, Buratti B, Capaccioni F, Cerroni P, Clark R, Combes M, Coradini A, Cruikshank D, Formisano V, Jaumann R, Langevin Y, Matson D, McCord T, Mennella V, Nelson R, Nicholson P, Sicardy B, Sotin C, Soderblom LA, and Kursinski R
- Subjects
- Atmosphere, Extraterrestrial Environment, Spacecraft, Spectrum Analysis, Methane, Saturn
- Abstract
Spectra from Cassini's Visual and Infrared Mapping Spectrometer reveal that the horizontal structure, height, and optical depth of Titan's clouds are highly dynamic. Vigorous cloud centers are seen to rise from the middle to the upper troposphere within 30 minutes and dissipate within the next hour. Their development indicates that Titan's clouds evolve convectively; dissipate through rain; and, over the next several hours, waft downwind to achieve their great longitude extents. These and other characteristics suggest that temperate clouds originate from circulation-induced convergence, in addition to a forcing at the surface associated with Saturn's tides, geology, and/or surface composition.
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- 2005
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7. Aeolian processes at the Mars Exploration Rover Meridiani Planum landing site.
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Sullivan R, Banfield D, Bell JF 3rd, Calvin W, Fike D, Golombek M, Greeley R, Grotzinger J, Herkenhoff K, Jerolmack D, Malin M, Ming D, Soderblom LA, Squyres SW, Thompson S, Watters WA, Weitz CM, and Yen A
- Abstract
The martian surface is a natural laboratory for testing our understanding of the physics of aeolian (wind-related) processes in an environment different from that of Earth. Martian surface markings and atmospheric opacity are time-variable, indicating that fine particles at the surface are mobilized regularly by wind. Regolith (unconsolidated surface material) at the Mars Exploration Rover Opportunity's landing site has been affected greatly by wind, which has created and reoriented bedforms, sorted grains, and eroded bedrock. Aeolian features here preserve a unique record of changing wind direction and wind strength. Here we present an in situ examination of a martian bright wind streak, which provides evidence consistent with a previously proposed formational model for such features. We also show that a widely used criterion for distinguishing between aeolian saltation- and suspension-dominated grain behaviour is different on Mars, and that estimated wind friction speeds between 2 and 3 m s(-1), most recently from the northwest, are associated with recent global dust storms, providing ground truth for climate model predictions.
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- 2005
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8. Release of volatiles from a possible cryovolcano from near-infrared imaging of Titan.
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Sotin C, Jaumann R, Buratti BJ, Brown RH, Clark RN, Soderblom LA, Baines KH, Bellucci G, Bibring JP, Capaccioni F, Cerroni P, Combes M, Coradini A, Cruikshank DP, Drossart P, Formisano V, Langevin Y, Matson DL, McCord TB, Nelson RM, Nicholson PD, Sicardy B, LeMouelic S, Rodriguez S, Stephan K, and Scholz CK
- Subjects
- Atmosphere chemistry, Gases chemistry, Geography, Hydrocarbons analysis, Hydrocarbons chemistry, Methane analysis, Methane chemistry, Spacecraft, Extraterrestrial Environment chemistry, Gases analysis, Ice analysis, Infrared Rays, Moon, Photography, Saturn
- Abstract
Titan is the only satellite in our Solar System with a dense atmosphere. The surface pressure is 1.5 bar (ref. 1) and, similar to the Earth, N2 is the main component of the atmosphere. Methane is the second most important component, but it is photodissociated on a timescale of 10(7) years (ref. 3). This short timescale has led to the suggestion that Titan may possess a surface or subsurface reservoir of hydrocarbons to replenish the atmosphere. Here we report near-infrared images of Titan obtained on 26 October 2004 by the Cassini spacecraft. The images show that a widespread methane ocean does not exist; subtle albedo variations instead suggest topographical variations, as would be expected for a more solid (perhaps icy) surface. We also find a circular structure approximately 30 km in diameter that does not resemble any features seen on other icy satellites. We propose that the structure is a dome formed by upwelling icy plumes that release methane into Titan's atmosphere.
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- 2005
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9. Evidence from Opportunity's Microscopic Imager for water on Meridiani Planum.
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Herkenhoff KE, Squyres SW, Arvidson R, Bass DS, Bell JF 3rd, Bertelsen P, Ehlmann BL, Farrand W, Gaddis L, Greeley R, Grotzinger J, Hayes AG, Hviid SF, Johnson JR, Jolliff B, Kinch KM, Knoll AH, Madsen MB, Maki JN, McLennan SM, McSween HY, Ming DW, Rice JW Jr, Richter L, Sims M, Smith PH, Soderblom LA, Spanovich N, Sullivan R, Thompson S, Wdowiak T, Weitz C, and Whelley P
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- Extraterrestrial Environment, Ferric Compounds, Geologic Sediments, Minerals, Silicates, Spacecraft, Mars, Water
- Abstract
The Microscopic Imager on the Opportunity rover analyzed textures of soils and rocks at Meridiani Planum at a scale of 31 micrometers per pixel. The uppermost millimeter of some soils is weakly cemented, whereas other soils show little evidence of cohesion. Rock outcrops are laminated on a millimeter scale; image mosaics of cross-stratification suggest that some sediments were deposited by flowing water. Vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis. Microscopic images support the hypothesis that hematite-rich spherules observed in outcrops and soils also formed diagenetically as concretions.
- Published
- 2004
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10. Localization and physical property experiments conducted by Opportunity at Meridiani Planum.
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Arvidson RE, Anderson RC, Bartlett P, Bell JF 3rd, Christensen PR, Chu P, Davis K, Ehlmann BL, Golombek MP, Gorevan S, Guinness EA, Haldemann AF, Herkenhoff KE, Landis G, Li R, Lindemann R, Ming DW, Myrick T, Parker T, Richter L, Seelos FP 4th, Soderblom LA, Squyres SW, Sullivan RJ, and Wilson J
- Subjects
- Extraterrestrial Environment, Geologic Sediments, Spacecraft, Wind, Mars
- Abstract
The location of the Opportunity landing site was determined to better than 10-m absolute accuracy from analyses of radio tracking data. We determined Rover locations during traverses with an error as small as several centimeters using engineering telemetry and overlapping images. Topographic profiles generated from rover data show that the plains are very smooth from meter- to centimeter-length scales, consistent with analyses of orbital observations. Solar cell output decreased because of the deposition of airborne dust on the panels. The lack of dust-covered surfaces on Meridiani Planum indicates that high velocity winds must remove this material on a continuing basis. The low mechanical strength of the evaporitic rocks as determined from grinding experiments, and the abundance of coarse-grained surface particles argue for differential erosion of Meridiani Planum.
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- 2004
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11. The Opportunity Rover's Athena science investigation at Meridiani Planum, Mars.
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Squyres SW, Arvidson RE, Bell JF 3rd, Brückner J, Cabrol NA, Calvin W, Carr MH, Christensen PR, Clark BC, Crumpler L, Marais DJ, d'Uston C, Economou T, Farmer J, Farrand W, Folkner W, Golombek M, Gorevan S, Grant JA, Greeley R, Grotzinger J, Haskin L, Herkenhoff KE, Hviid S, Johnson J, Klingelhöfer G, Knoll AH, Landis G, Lemmon M, Li R, Madsen MB, Malin MC, McLennan SM, McSween HY, Ming DW, Moersch J, Morris RV, Parker T, Rice JW Jr, Richter L, Rieder R, Sims M, Smith M, Smith P, Soderblom LA, Sullivan R, Wänke H, Wdowiak T, Wolff M, and Yen A
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- Atmosphere, Evolution, Planetary, Extraterrestrial Environment, Ferric Compounds, Geologic Sediments, Minerals, Silicates, Spacecraft, Water, Wind, Mars
- Abstract
The Mars Exploration Rover Opportunity has investigated the landing site in Eagle crater and the nearby plains within Meridiani Planum. The soils consist of fine-grained basaltic sand and a surface lag of hematite-rich spherules, spherule fragments, and other granules. Wind ripples are common. Underlying the thin soil layer, and exposed within small impact craters and troughs, are flat-lying sedimentary rocks. These rocks are finely laminated, are rich in sulfur, and contain abundant sulfate salts. Small-scale cross-lamination in some locations provides evidence for deposition in flowing liquid water. We interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water, followed by evaporation, exposure, and desiccation. Hematite-rich spherules are embedded in the rock and eroding from them. We interpret these spherules to be concretions formed by postdepositional diagenesis, again involving liquid water.
- Published
- 2004
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12. Soils of Eagle crater and Meridiani Planum at the Opportunity Rover landing site.
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Soderblom LA, Anderson RC, Arvidson RE, Bell JF 3rd, Cabrol NA, Calvin W, Christensen PR, Clark BC, Economou T, Ehlmann BL, Farrand WH, Fike D, Gellert R, Glotch TD, Golombek MP, Greeley R, Grotzinger JP, Herkenhoff KE, Jerolmack DJ, Johnson JR, Jolliff B, Klingelhöfer G, Knoll AH, Learner ZA, Li R, Malin MC, McLennan SM, McSween HY, Ming DW, Morris RV, Rice JW Jr, Richter L, Rieder R, Rodionov D, Schröder C, Seelos FP 4th, Soderblom JM, Squyres SW, Sullivan R, Watters WA, Weitz CM, Wyatt MB, Yen A, and Zipfel J
- Subjects
- Extraterrestrial Environment, Ferric Compounds, Geologic Sediments, Minerals, Silicates, Spacecraft, Spectrum Analysis, Water, Mars
- Abstract
The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.
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- 2004
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13. Pancam multispectral imaging results from the Opportunity Rover at Meridiani Planum.
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Bell JF 3rd, Squyres SW, Arvidson RE, Arneson HM, Bass D, Calvin W, Farrand WH, Goetz W, Golombek M, Greeley R, Grotzinger J, Guinness E, Hayes AG, Hubbard MY, Herkenhoff KE, Johnson MJ, Johnson JR, Joseph J, Kinch KM, Lemmon MT, Li R, Madsen MB, Maki JN, Malin M, McCartney E, McLennan S, McSween HY Jr, Ming DW, Morris RV, Dobrea EZ, Parker TJ, Proton J, Rice JW Jr, Seelos F, Soderblom JM, Soderblom LA, Sohl-Dickstein JN, Sullivan RJ, Weitz CM, and Wolff MJ
- Subjects
- Atmosphere, Extraterrestrial Environment, Ferric Compounds, Geologic Sediments, Ice, Silicates, Spacecraft, Spectrum Analysis, Water, Mars
- Abstract
Panoramic Camera (Pancam) images from Meridiani Planum reveal a low-albedo, generally flat, and relatively rock-free surface. Within and around impact craters and fractures, laminated outcrop rocks with higher albedo are observed. Fine-grained materials include dark sand, bright ferric iron-rich dust, angular rock clasts, and millimeter-size spheroidal granules that are eroding out of the laminated rocks. Spectra of sand, clasts, and one dark plains rock are consistent with mafic silicates such as pyroxene and olivine. Spectra of both the spherules and the laminated outcrop materials indicate the presence of crystalline ferric oxides or oxyhydroxides. Atmospheric observations show a steady decline in dust opacity during the mission. Astronomical observations captured solar transits by Phobos and Deimos and time-lapse observations of sunsets.
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- 2004
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14. In situ evidence for an ancient aqueous environment at Meridiani Planum, Mars.
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Squyres SW, Grotzinger JP, Arvidson RE, Bell JF 3rd, Calvin W, Christensen PR, Clark BC, Crisp JA, Farrand WH, Herkenhoff KE, Johnson JR, Klingelhöfer G, Knoll AH, McLennan SM, McSween HY Jr, Morris RV, Rice JW Jr, Rieder R, and Soderblom LA
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- Exobiology, Extraterrestrial Environment, Ferric Compounds, Geologic Sediments, Life, Minerals, Silicates, Spacecraft, Spectrum Analysis, Sulfates, Sulfur, Mars, Water
- Abstract
Sedimentary rocks at Eagle crater in Meridiani Planum are composed of fine-grained siliciclastic materials derived from weathering of basaltic rocks, sulfate minerals (including magnesium sulfate and jarosite) that constitute several tens of percent of the rock by weight, and hematite. Cross-stratification observed in rock outcrops indicates eolian and aqueous transport. Diagenetic features include hematite-rich concretions and crystal-mold vugs. We interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history. The environmental conditions that they record include episodic inundation by shallow surface water, evaporation, and desiccation. The geologic record at Meridiani Planum suggests that conditions were suitable for biological activity for a period of time in martian history.
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- 2004
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15. Pancam multispectral imaging results from the Spirit Rover at Gusev Crater.
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Bell JF 3rd, Squyres SW, Arvidson RE, Arneson HM, Bass D, Blaney D, Cabrol N, Calvin W, Farmer J, Farrand WH, Goetz W, Golombek M, Grant JA, Greeley R, Guinness E, Hayes AG, Hubbard MY, Herkenhoff KE, Johnson MJ, Johnson JR, Joseph J, Kinch KM, Lemmon MT, Li R, Madsen MB, Maki JN, Malin M, McCartney E, McLennan S, McSween HY Jr, Ming DW, Moersch JE, Morris RV, Dobrea EZ, Parker TJ, Proton J, Rice JW Jr, Seelos F, Soderblom J, Soderblom LA, Sohl-Dickstein JN, Sullivan RJ, Wolff MJ, and Wang A
- Subjects
- Atmosphere, Evolution, Planetary, Extraterrestrial Environment, Ferric Compounds, Geologic Sediments, Iron Compounds, Minerals, Silicates, Solar System, Spectrum Analysis, Water, Mars
- Abstract
Panoramic Camera images at Gusev crater reveal a rock-strewn surface interspersed with high- to moderate-albedo fine-grained deposits occurring in part as drifts or in small circular swales or hollows. Optically thick coatings of fine-grained ferric iron-rich dust dominate most bright soil and rock surfaces. Spectra of some darker rock surfaces and rock regions exposed by brushing or grinding show near-infrared spectral signatures consistent with the presence of mafic silicates such as pyroxene or olivine. Atmospheric observations show a steady decline in dust opacity during the mission, and astronomical observations captured solar transits by the martian moons, Phobos and Deimos, as well as a view of Earth from the martian surface.
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- 2004
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16. The Spirit Rover's Athena science investigation at Gusev Crater, Mars.
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Squyres SW, Arvidson RE, Bell JF 3rd, Brückner J, Cabrol NA, Calvin W, Carr MH, Christensen PR, Clark BC, Crumpler L, Des Marais DJ, D'Uston C, Economou T, Farmer J, Farrand W, Folkner W, Golombek M, Gorevan S, Grant JA, Greeley R, Grotzinger J, Haskin L, Herkenhoff KE, Hviid S, Johnson J, Klingelhöfer G, Knoll A, Landis G, Lemmon M, Li R, Madsen MB, Malin MC, McLennan SM, McSween HY, Ming DW, Moersch J, Morris RV, Parker T, Rice JW Jr, Richter L, Rieder R, Sims M, Smith M, Smith P, Soderblom LA, Sullivan R, Wänke H, Wdowiak T, Wolff M, and Yen A
- Subjects
- Atmosphere, Extraterrestrial Environment, Geologic Sediments, Geological Phenomena, Geology, Magnetics, Minerals, Water, Wind, Mars
- Abstract
The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.
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- 2004
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17. Textures of the soils and rocks at Gusev Crater from Spirit's Microscopic Imager.
- Author
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Herkenhoff KE, Squyres SW, Arvidson R, Bass DS, Bell JF 3rd, Bertelsen P, Cabrol NA, Gaddis L, Hayes AG, Hviid SF, Johnson JR, Kinch KM, Madsen MB, Maki JN, McLennan SM, McSween HY, Rice JW Jr, Sims M, Smith PH, Soderblom LA, Spanovich N, Sullivan R, and Wang A
- Subjects
- Extraterrestrial Environment, Geologic Sediments, Volcanic Eruptions, Water, Wind, Mars
- Abstract
The Microscopic Imager on the Spirit rover analyzed the textures of the soil and rocks at Gusev crater on Mars at a resolution of 100 micrometers. Weakly bound agglomerates of dust are present in the soil near the Columbia Memorial Station. Some of the brushed or abraded rock surfaces show igneous textures and evidence for alteration rinds, coatings, and veins consistent with secondary mineralization. The rock textures are consistent with a volcanic origin and subsequent alteration and/or weathering by impact events, wind, and possibly water.
- Published
- 2004
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18. Observations of comet 19P/Borrelly by the miniature integrated camera and spectrometer aboard Deep Space 1.
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Soderblom LA, Becker TL, Bennett G, Boice DC, Britt DT, Brown RH, Buratti BJ, Isbell C, Giese B, Hare T, Hicks MD, Howington-Kraus E, Kirk RL, Lee M, Nelson RM, Oberst J, Owen TC, Rayman MD, Sandel BR, Stern SA, Thomas N, and Yelle RV
- Subjects
- Carbon analysis, Cosmic Dust, Hydrocarbons analysis, Spectrum Analysis, Temperature, Meteoroids
- Abstract
The nucleus of the Jupiter-family comet 19P/Borrelly was closely observed by the Miniature Integrated Camera and Spectrometer aboard the Deep Space 1 spacecraft on 22 September 2001. The 8-kilometer-long body is highly variegated on a scale of 200 meters, exhibiting large albedo variations (0.01 to 0.03) and complex geologic relationships. Short-wavelength infrared spectra (1.3 to 2.6 micrometers) show a slope toward the red and a hot, dry surface (=345 kelvin, with no trace of water ice or hydrated minerals), consistent with approximately 10% or less of the surface actively sublimating. Borrelly's coma exhibits two types of dust features: fans and highly collimated jets. At encounter, the near-nucleus coma was dominated by a prominent dust jet that resolved into at least three smaller jets emanating from a broad basin in the middle of the nucleus. Because the major dust jet remained fixed in orientation, it is evidently aligned near the rotation axis of the nucleus.
- Published
- 2002
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19. A close-up look at Io from Galileo's near-infrared mapping spectrometer.
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Lopes-Gautier R, Douté S, Smythe WD, Kamp LW, Carlson RW, Davies AG, Leader FE, McEwen AS, Geissler PE, Kieffer SW, Keszthelyi L, Barbinis E, Mehlman R, Segura M, Shirley J, and Soderblom LA
- Subjects
- Extraterrestrial Environment, Hot Temperature, Spectroscopy, Near-Infrared methods, Sunlight, Temperature, Jupiter, Spacecraft, Volcanic Eruptions
- Abstract
Infrared spectral images of Jupiter's volcanic moon Io, acquired during the October and November 1999 and February 2000 flybys of the Galileo spacecraft, were used to study the thermal structure and sulfur dioxide distribution of active volcanoes. Loki Patera, the solar system's most powerful known volcano, exhibits large expanses of dark, cooling lava on its caldera floor. Prometheus, the site of long-lived plume activity, has two major areas of thermal emission, which support ideas of plume migration. Sulfur dioxide deposits were mapped at local scales and show a more complex relationship to surface colors than previously thought, indicating the presence of other sulfur compounds.
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- 2000
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20. North-south geological differences between the residual polar caps on Mars.
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Thomas PC, Malin MC, Edgett KS, Carr MH, Hartmann WK, Ingersoll AP, James PB, Soderblom LA, Veverka J, and Sullivan R
- Subjects
- Carbon Dioxide analysis, Evolution, Planetary, Extraterrestrial Environment, Mars
- Abstract
Polar processes can be sensitive indicators of global climate, and the geological features associated with polar ice caps can therefore indicate evolution of climate with time. The polar regions on Mars have distinctive morphologic and climatologic features: thick layered deposits, seasonal CO2 frost caps extending to mid latitudes, and near-polar residual frost deposits that survive the summer. The relationship of the seasonal and residual frost caps to the layered deposits has been poorly constrained, mainly by the limited spatial resolution of the available data. In particular, it has not been known if the residual caps represent simple thin frost cover or substantial geologic features. Here we show that the residual cap on the south pole is a distinct geologic unit with striking collapse and erosional topography; this is very different from the residual cap on the north pole, which grades into the underlying layered materials. These findings indicate that the differences between the caps are substantial (rather than reflecting short-lived differences in frost cover), and so support the idea of long-term asymmetry in the polar climates of Mars.
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- 2000
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21. Hydrogen peroxide on the surface of Europa.
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Carlson RW, Anderson MS, Johnson RE, Smythe WD, Hendrix AR, Barth CA, Soderblom LA, Hansen GB, McCord TB, Dalton JB, Clark RN, Shirley JH, Ocampo AC, and Matson DL
- Subjects
- Hydrogen Peroxide chemistry, Ice, Spectrophotometry, Infrared, Spectrophotometry, Ultraviolet, Water chemistry, Extraterrestrial Environment, Hydrogen Peroxide analysis, Jupiter
- Abstract
Spatially resolved infrared and ultraviolet wavelength spectra of Europa's leading, anti-jovian quadrant observed from the Galileo spacecraft show absorption features resulting from hydrogen peroxide. Comparisons with laboratory measurements indicate surface hydrogen peroxide concentrations of about 0.13 percent, by number, relative to water ice. The inferred abundance is consistent with radiolytic production of hydrogen peroxide by intense energetic particle bombardment and demonstrates that Europa's surface chemistry is dominated by radiolysis.
- Published
- 1999
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22. Early views of the martian surface from the Mars Orbiter Camera of Mars Global Surveyor.
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Malin MC, Carr MH, Danielson GE, Davies ME, Hartmann WK, Ingersoll AP, James PB, Masursky H, McEwen AS, Soderblom LA, Thomas P, Veverka J, Caplinger MA, Ravine MA, Soulanille TA, and Warren JL
- Subjects
- Carbon Dioxide, Ice, Spacecraft, Extraterrestrial Environment, Mars
- Abstract
High-resolution images of the martian surface at scales of a few meters show ubiquitous erosional and depositional eolian landforms. Dunes, sandsheets, and drifts are prevalent and exhibit a range of morphology, composition (inferred from albedo), and age (as seen in occurrences of different dune orientations at the same location). Steep walls of topographic depressions such as canyons, valleys, and impact craters show the martian crust to be stratified at scales of a few tens of meters. The south polar layered terrain and superposed permanent ice cap display diverse surface textures that may reflect the complex interplay of volatile and non-volatile components. Low resolution regional views of the planet provide synoptic observations of polar cap retreat, condensate clouds, and the lifecycle of local and regional dust storms.
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- 1998
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23. Results from the Mars Pathfinder camera.
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Smith PH, Bell JF 3rd, Bridges NT, Britt DT, Gaddis L, Greeley R, Keller HU, Herkenhoff KE, Jaumann R, Johnson JR, Kirk RL, Lemmon M, Maki JN, Malin MC, Murchie SL, Oberst J, Parker TJ, Reid RJ, Sablotny R, Soderblom LA, Stoker C, Sullivan R, Thomas N, Tomasko MG, and Wegryn E
- Subjects
- Atmosphere, Ice, Minerals, Wind, Extraterrestrial Environment, Mars, Water
- Abstract
Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (at 440- to 1000-nanometer wavelength) reveal three types of rock and four classes of soil. Upward-looking IMP images of the predawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity approximately 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers.
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- 1997
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24. Galileo infrared imaging spectroscopy measurements at venus.
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Carlson RW, Baines KH, Encrenaz T, Taylor FW, Drossart P, Kamp LW, Pollack JB, Lellouch E, Collard AD, Calcutt SB, Grinspoon D, Weissman PR, Smythe WD, Ocampo AC, Danielson GE, Fanale FP, Johnson TV, Kieffer HH, Matson DL, McCord TB, and Soderblom LA
- Abstract
During the 1990 Galileo Venus flyby, the Near Infaied Mapping Spectrometer investigated the night-side atmosphere of Venus in the spectral range 0.7 to 5.2 micrometers. Multispectral images at high spatial resolution indicate substanmial cloud opacity variations in the lower cloud levels, centered at 50 kilometers altitude. Zonal and meridional winds were derived for this level and are consistent with motion of the upper branch of a Hadley cell. Northern and southern hemisphere clouds appear to be markedly different. Spectral profiles were used to derive lower atmosphere abundances of water vapor and other species.
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- 1991
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25. Impact craters on venus: initial analysis from magellan.
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Phillips RJ, Arvidson RE, Boyce JM, Campbell DB, Guest JE, Schaber GG, and Soderblom LA
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Magellan radar images of 15 percent of the planet show 135 craters of probable impact origin. Craters more than 15 km across tend to contain central peaks, multiple central peaks, and peak rings. Many craters smaller than 15 km exhibit multiple floors or appear in clusters; these phenomena are attributed to atmospheric breakup of incoming meteoroids. Additionally, the atmosphere appears to have prevented the formation of primary impact craters smaller than about 3 km and produced a deficiency in the number of craters smaller than about 25 km across. Ejecta is found at greater distances than that predicted by simple ballistic emplacement, and the distal ends of some ejecta deposits are lobate. These characteristics may represent surface flows of material initially entrained in the atmosphere. Many craters are surrounded by zones of low radar albedo whose origin may have been deformation of the surface by the shock or pressure wave associated with the incoming meteoroid. Craters are absent from several large areas such as a 5 million square kilometer region around Sappho Patera, where the most likely explanation for the dearth of craters is volcanic resurfacing. There is apparently a spectrum of surface ages on Venus ranging approximately from 0 to 800 million years, and therefore Venus must be a geologically active planet.
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- 1991
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26. Magellan: radar performance and data products.
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Pettengill GH, Ford PG, Johnson WT, Raney RK, and Soderblom LA
- Abstract
The Magellan Venus orbiter carries only one scientific instrument: a 12.6-centimeter wavelength radar system shared among three data-taking modes. The synthetic-aperture mode images radar echoes from the Venus surface at a resolution of between 120 and 300 meters, depending on spacecraft altitude. In the altimetric mode, relative height measurement accuracies may approach 5 meters, depending on the terrain's roughness, although orbital uncertainties place a floor of about 50 meters on the absolute uncertainty. In areas of extremely rough topography, accuracy is limited by the inherent line-of-sight radar resolution of about 88 meters. The maximum elevation observed to date, corresponding to a planetary radius of 6062 kilometers, lies within Maxwell Mons. When used as a thermal emission radiometer, the system can determine surface emissivities to an absolute accuracy of about 0.02. Mosaicked and archival digital data products will be released in compact disk (CDROM) format.
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- 1991
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27. Subsurface energy storage and transport for solar-powered geysers on triton.
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Kirk RL, Brown RH, and Soderblom LA
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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-greenhouse layer and for the supply of gas and energy to a geyser are examined. "Leaky greenhouse" models with only vertical gas transport are inconsistent with the observed upper limit on geyser radius of approximately 1.5 kilometers. However, lateral transport of energy by gas flow in a porous N(2) layer with a block size on the order of a meter can supply the required amount of gas to a source region approximately 1 kilometer in radius. The decline of gas output to steady state may occur over a period comparable with the inferred active geyser lifetime of five Earth years. The required subsurface permeability may be maintained by thermal fracturing of the residual N2 polar cap. A lower limit on geyser source radius of approximately 50 to 100 meters predicted by a theory of negatively buoyant jets is not readily attained.
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- 1990
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28. Energy Sources for Triton's Geyser-Like Plumes.
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Brown RH, Kirk RL, Johnson TV, and Soderblom LA
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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 (in a solid-state greenhouse), which is subsequently released in the form of latent heat of sublimation, could provide the required energy. Both the classical solid-state greenhouse consisting of exponentially absorbed insolation in a gray, translucent layer of solid nitrogen, and the "super" greenhouse consisting of a relatively transparent solid-nitrogen layer over an opaque, absorbing layer are plausible candidates. Geothermal heat may also play a part if assisted by the added energy input of seasonal cycles of insolation.
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- 1990
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29. Triton's Geyser-Like Plumes: Discovery and Basic Characterization.
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Soderblom LA, Kieffer SW, Becker TL, Brown RH, Cook AF 2nd, Hansen CJ, Johnson TV, Kirk RL, and Shoemaker EM
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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 appear to be in the range of several tens of meters to a kilometer. One model for the mechanism to drive the plumes involves heating of nitrogen ice in a subsurface greenhouse environment; nitrogen gas pressurized by the solar heating explosively vents to the surface carrying clouds of ice and dark partides into the atmosphere. A temperature increase of less than 4 kelvins above the ambient surface value of 38 +/- 3 kelvins is more than adequate to drive the plumes to an 8-kilometer altitude. The mass flux in the trailing clouds is estimated to consist of up to 10 kilograms of fine dark particles per second or twice as much nitrogen ice and perhaps several hundred or more kilograms of nitrogen gas per second. Each eruption may last a year or more, during which on the order of a tenth of a cubic kilometer of ice is sublimed.
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- 1990
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30. The galilean satellites and jupiter: voyager 2 imaging science results.
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Smith BA, Soderblom LA, Beebe R, Boyce J, Briggs G, Carr M, Collins SA, Cook AF 2nd, Danielson GE, Davies ME, Hunt GE, Ingersoll A, Johnson TV, Masursky H, McCauley J, Morrison D, Owen T, Sagan C, Shoemaker EM, Strom R, Suomi VE, and Veverka J
- Abstract
Voyager 2, during its encounter with the Jupiter system, provided images that both complement and supplement in important ways the Voyager 1 images. While many changes have been observed in Jupiter's visual appearance, few, yet significant, changes have been detected in the principal atmospheric currents. Jupiter's ring system is strongly forward scattering at visual wavelengths and consists of a narrow annulus of highest particle density, within which is a broader region in which the density is lower. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but does reveal a complex and, as yet, little-understood system of overlapping bright and dark linear features. Ganymede is found to have at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered.
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- 1979
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31. Voyager 2 at neptune: imaging science results.
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Smith BA, Soderblom LA, Banfield D, Barnet C, Basilevsky AT, Beebe RF, Bollinger K, Boyce JM, Brahic A, Briggs GA, Brown RH, Chyba C, Collins SA, Colvin T, Cook AF 2nd, Crisp D, Croft SK, Cruikshank D, Cuzzi JN, Danielson GE, Davies ME, De Jong E, Dones L, Godfrey D, Goguen J, Grenier I, Haemmerle VR, Hammel H, Hansen CJ, Helfenstein CP, Howell C, Hunt GE, Ingersoll AP, Johnson TV, Kargel J, Kirk R, Kuehn DI, Limaye S, Masursky H, McEwen A, Morrison D, Owen T, Owen W, Pollack JB, Porco CC, Rages K, Rogers P, Rudy D, Sagan C, Schwartz J, Shoemaker EM, Showalter M, Sicardy B, Simonelli D, Spencer J, Sromovsky LA, Stoker C, Strom RG, Suomi VE, Synott SP, Terrile RJ, Thomas P, Thompson WR, Verbiscer A, and Veverka J
- Abstract
Voyager 2 images of Neptune reveal a windy planet characterized by bright clouds of methane ice suspended in an exceptionally clear atmosphere above a lower deck of hydrogen sulfide or ammonia ices. Neptune's atmosphere is dominated by a large anticyclonic storm system that has been named the Great Dark Spot (GDS). About the same size as Earth in extent, the GDS bears both many similarities and some differences to the Great Red Spot of Jupiter. Neptune's zonal wind profile is remarkably similar to that of Uranus. Neptune has three major rings at radii of 42,000, 53,000, and 63,000 kilometers. The outer ring contains three higher density arc-like segments that were apparently responsible for most of the ground-based occultation events observed during the current decade. Like the rings of Uranus, the Neptune rings are composed of very dark material; unlike that of Uranus, the Neptune system is very dusty. Six new regular satellites were found, with dark surfaces and radii ranging from 200 to 25 kilometers. All lie inside the orbit of Triton and the inner four are located within the ring system. Triton is seen to be a differentiated body, with a radius of 1350 kilometers and a density of 2.1 grams per cubic centimeter; it exhibits clear evidence of early episodes of surface melting. A now rigid crust of what is probably water ice is overlain with a brilliant coating of nitrogen frost, slightly darkened and reddened with organic polymer material. Streaks of organic polymer suggest seasonal winds strong enough to move particles of micrometer size or larger, once they become airborne. At least two active plumes were seen, carrying dark material 8 kilometers above the surface before being transported downstream by high level winds. The plumes may be driven by solar heating and the subsequent violent vaporization of subsurface nitrogen.
- Published
- 1989
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32. The jupiter system through the eyes of voyager 1.
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Smith BA, Soderblom LA, Johnson TV, Ingersoll AP, Collins SA, Shoemaker EM, Hunt GE, Masursky H, Carr MH, Davies ME, Cook AF 2nd, Boyce J, Danielson GE, Owen T, Sagan C, Beebe RF, Veverka J, Strom RG, McCauley JF, Morrison D, Briggs GA, and Suomi VE
- Abstract
The cameras aboard Voyager 1 have provided a closeup view of the Jupiter system, revealing heretofore unknown characteristics and phenomena associated with the planet's atmosphere and the surfaces of its five major satellites. On Jupiter itself, atmospheric motions-the interaction of cloud systems-display complex vorticity. On its dark side, lightning and auroras are observed. A ring was discovered surrounding Jupiter. The satellite surfaces display dramatic differences including extensive active volcanismn on Io, complex tectonism on Ganymnede and possibly Europa, and flattened remnants of enormous impact features on Callisto.
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- 1979
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33. Preliminary results from the viking orbiter imaging experiment.
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Carr MH, Masursky H, Baum WA, Blasius KR, Briggs GA, Cutts JA, Duxbury T, Greeley R, Guest JE, Smith BA, Soderblom LA, Veverka J, and Wellman JB
- Abstract
During its first 30 orbits around Mars, the Viking orbiter took approximately 1000 photographic frames of the surface of Mars with resolutions that ranged from 100 meters to a little more than 1 kilometer. Most were of potential landing sites in Chryse Planitia and Cydonia and near Capri Chasma. Contiguous high-resolution coverage in these areas has led to an increased understanding of surface processes, particularly cratering, fluvial, and mass-wasting phenomena. Most of the surfaces examined appear relatively old, channel features abound, and a variety of features suggestive of permafrost have been identified. The ejecta patterns around large craters imply that fluid flow of ejecta occurred after ballistic deposition. Variable features in the photographed area appear to have changed little since observed 5 years ago from Mariner 9. A variety of atmospheric phenomena were observed, including diffuse morning hazes, both stationary and moving discrete white clouds, and wave clouds covering extensive areas.
- Published
- 1976
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34. Lunar surface chemistry: a new imaging technique.
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Andre CG, Bielefeld MJ, Eliason E, Soderblom LA, Adler I, and Philpotts JA
- Abstract
Detailed chemical maps of the lunar surface have been constructed by applying a new weighted-filter imaging technique to Apollo 15 and Apollo 16 x-ray fluorescence data. The data quality improvement is amply demonstrated by (i) modes in the frequency distribution, representing highland and mare soil suites, which are not evident before data filtering and (ii) numerous examples of chemical variations which are correlated with small-scale (about 15 kilometer) lunar topographic features.
- Published
- 1977
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35. Voyager 2 in the uranian system: imaging science results.
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Smith BA, Soderblom LA, Beebe R, Bliss D, Boyce JM, Brahic A, Briggs GA, Brown RH, Collins SA, Cook AF 2nd, Croft SK, Cuzzi JN, Danielson GE, Davies ME, Dowling TE, Godfrey D, Hansen CJ, Harris C, Hunt GE, Ingersoll AP, Johnson TV, Krauss RJ, Masursky H, Morrison D, Owen T, Plescia JB, Pollack JB, Porco CC, Rages K, Sagan C, Shoemaker EM, Sromovsky LA, Stoker C, Strom RG, Suomi VE, Synnott SP, Terrile RJ, Thomas P, Thompson WR, and Veverka J
- Abstract
Voyager 2 images of the southern hemisphere of Uranus indicate that submicrometersize haze particles and particles of a methane condensation cloud produce faint patterns in the atmosphere. The alignment of the cloud bands is similar to that of bands on Jupiter and Saturn, but the zonal winds are nearly opposite. At mid-latitudes (-70 degrees to -27 degrees ), where winds were measured, the atmosphere rotates faster than the magnetic field; however, the rotation rate of the atmosphere decreases toward the equator, so that the two probably corotate at about -20 degrees . Voyager images confirm the extremely low albedo of the ring particles. High phase angle images reveal on the order of 10(2) new ringlike features of very low optical depth and relatively high dust abundance interspersed within the main rings, as well as a broad, diffuse, low optical depth ring just inside the main rings system. Nine of the newly discovered small satellites (40 to 165 kilometers in diameter) orbit between the rings and Miranda; the tenth is within the ring system. Two of these small objects may gravitationally confine the e ring. Oberon and Umbriel have heavily cratered surfaces resembling the ancient cratered highlands of Earth's moon, although Umbriel is almost completely covered with uniform dark material, which perhaps indicates some ongoing process. Titania and Ariel show crater populations different from those on Oberon and Umbriel; these were probably generated by collisions with debris confined to their orbits. Titania and Ariel also show many extensional fault systems; Ariel shows strong evidence for the presence of extrusive material. About halfof Miranda's surface is relatively bland, old, cratered terrain. The remainder comprises three large regions of younger terrain, each rectangular to ovoid in plan, that display complex sets of parallel and intersecting scarps and ridges as well as numerous outcrops of bright and dark materials, perhaps suggesting some exotic composition.
- Published
- 1986
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36. Viking orbital colorimetric images of Mars: preliminary results.
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Soderblom LA
- Abstract
Color reconstruction and ratios of orbital images of Mars confirm Earth-based measurements showing red/violet ratios for bright areas to be roughly 1.5 times greater than dark areas. The new results show complex variation among dark materials; dark streaks emanating from craters in southern cratered terrains are much bluer than dark materials of the north equatorial plains on which Viking 1 landed.
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- 1976
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37. Mariner 9 television reconnaissance of Mars and its satellites: preliminary results.
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Masursky H, Batson RM, McCauley JF, Soderblom LA, Wildey RL, Carr MH, Milton DJ, Wilhelms DE, Smith BA, Kirby TB, Robinson JC, Leovy CB, Briggs GA, Duxbury TC, Acton CH Jr, Murray BC, Cutts JA, Sharp RP, Smith S, Leighton RB, Sagan C, Veverka J, Noland M, Lederberg J, Levinthal E, Pollack JB, Moore JT Jr, Hartmann WK, Shipley EN, De Vaucouleurs G, and Davies ME
- Abstract
At orbit insertion on 14 November 1971 the Martian surface was largely obscured by a dust haze with an extinction optical depth that ranged from near unity in the south polar region to probably greater than 2 over most of the planet. The only features clearly visible were the south polar cap, one dark, spot in Nix Olympica, and three dark spots in the Tharsis region. During the third week the atmosphere began to clear and surface visibility improved, but contrasts remained a fraction of their normal value. Each of the dark spots that apparently protrude through most of the dust-filled atmosphere has a crater or crater complex in its center. The craters are rimless and have featureless floors that, in the crater complexes, are at different levels. The largest crater within the southernmost spot is approximately 100 kilometers wide. The craters apparently were formed by subsidence and resemble terrestrial calderas. The south polar cap has a regular margin, suggsting very flat topography. Two craters outside the cap have frost on their floors; an apparent crater rim within the cap is frost free, indicating preferentia loss of frost from elevated ground. If this is so then the curvilinear streaks, which were frost covered in 1969 and are now clear of frost, may be low-relief ridges. Closeup pictures of Phobos and Deimos show that Phobos is about 25 +/-5 by 21 +/-1 kilometers and Deimos is about 13.5 +/- 2 by 12.0 +/-0.5 kilometers. Both have irregular shapes and are highly cratered, with some craters showing raised rims. The satellites are dark objects with geometric albedos of 0.05.
- Published
- 1972
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