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At least 379 records · Page 21

Geology Before Pluto: Pre-Encounter Considerations

Pluto, its large satellite Charon, and its four known satellites represent the first trans-Neptunian Kuiper Belt objects populating the outer-most solar system beyond the gas giant planets to be studied in detail from a spacecraft (New Horizons). A complete picture of the solar nebula, and solar system formation cannot be confidently formulated until representatives of this group of bodies at the edge of solar space have been examined. The Pluto system is composed of unique lunar- and intermediate-sized objects that can tell us much about how objects with volatile icy compositions evolve. Modeling of the interior suggests that geologic activity may have been to some degree, and observations of frost on the surface could imply the need for a geologic reservoir for the replenishment of these phases. However, the putative indicators of Pluto's geologic history are inconclusive and unspecific. Detailed examination of Pluto's geologic record is the only plausible means of bridging the gap between theory and observations. In this talk I will examine the potential importance of these tentative indications of geologic activity and how specific spacecraft observations have been designed and used to constrain the Pluto system's geologic history. The cameras of New Horizons will provide robust data sets that should be immanently amenable to geological analysis of the Pluto System's landscapes. In this talk, we begin with a brief discussion of the planned observations by New Horizons' cameras that will bear most directly on geological interpretability. Then I will broadly review major geological processes that could potentially operate of the surfaces of Pluto and its moons. I will first survey exogenic processes (i.e., those for which energy for surface modification is supplied externally to the planetary surface): impact cratering, sedimentary processes (including volatile migration) and the work of wind. I will conclude with an assessment of prospects for endogenic activity in the form of tectonics and cryo-volcanism.

Pluto↗

The Multispectral Microscopic Imager: Integrating Microimaging with Spectroscopy for the In-Situ Exploration of the Moon

To maximize the scientific return, future robotic and human missions to the Moon will need to have in-situ capabilities to enable the selection of the highest value samples for returning to Earth, or a lunar base for analysis. In order to accomplish this task efficiently, samples will need to be characterized using a suite of robotic instruments that can provide crucial information about elemental composition, mineralogy, volatiles and ices. Such spatially-correlated data sets, which place mineralogy into a microtextural context, are considered crucial for correct petrogenetic interpretations. . Combining microscopic imaging with visible= nearinfrared reflectance spectroscopy, provides a powerful in-situ approach for obtaining mineralogy within a microtextural context. The approach is non-destructive and requires minimal mechanical sample preparation. This approach provides data sets that are comparable to what geologists routinely acquire in the field, using a hand lens and in the lab using thin section petrography, and provide essential information for interpreting the primary formational processes in rocks and soils as well as the effects of secondary (diagenetic) alteration processes. Such observations lay a foundation for inferring geologic histories and provide "ground truth" for similar instruments on orbiting satellites; they support astronaut EVA activities and provide basic information about the physical properties of soils required for assessing associated health risks, and are basic tools in the exploration for in-situ resources to support human exploration of the Moon.

Nunez, J. I.↗

A Survey of Geologic Resources

This chapter focuses on the resources available from the Moon itself: regolith, geologically concentrated materials, and lunar physical features that will enable habitation and generation of power on the surface. This chapter briefly covers the formation of the Moon and thus the formation of the crust of the Moon, as well as the evolution of the regolith. The characteristics of the regolith are provided in some detail, including its mineralogy and lithology. The location of high concentrations of specific minerals or rocks is noted. Other ideal locations for in situ resource utilization technology and lunar habitation are presented. This chapter is intended to be a brief review of current knowledge, and to serve as a foundational source for further study. Each concept presented here has a wealth of literature associated with it; the reader is therefore directed to that literature with each discussion. With great interest in possible manned lunar landings and continued study of the Moon by multiple satellites, the available information changes regularly.

Edmonson, Jennifer↗

Earth's early atmosphere as seen from carbon and nitrogen isotopic analysis of Archean sediments

The origin and evolution of the Earth's early atmosphere has long been a topic of great interest but determination of actual compositions over geologic time is a difficult problem. However, recent systematic studies of stromatolite deposits (Precambrian Paleobiology Research Group) has extended our knowledge of Archean ecosystems. It has been shown that many stromatolite deposits have undergone negligible alteration since their time of formation. The discovery of primary fluid inclusions within unaltered 3.5 b.y. old Archiean sediments and the observation that the 3.3 b.y. old Barberton cherts have remained closed to argon loss and have not been subjected to thermal metamorphism suggests that an opportunity exists for the direct measurement of the volatile constituents present at their time of formation. Of primary interest to this study was the possibility that the stromatolites and other Archean sediments might retain a vestige of the atmosphere and thus afford an indication of the variations in carbon dioxide and nitrogen isotopic compositions with time. A suite of essentially unaltered Archean stromatolites and the cherts of different ages and geologic sites have been analyzed for their trapped carbon dioxide and nitrogen compositions by the stepped combustion extraction tech nique utilizing static mass spectrometers for the isotope measurements.

Gibson, E. K., Jr.↗

Geological Map of the Fredegonde (V-57) Quadrangle, Venus

The area of V-57, the Fredegonde quadrangle (50-75degS, 60-120degE, Fig.1), is located within the eastern portion of Lada Terra within the topographic province of midlands (0-2 km above MPR [1,2]). Midlands form the most abundant portion of the surface of Venus and are characterized by diverse sets of units and structures [3-11]. The area of the Fredegonde quadrangle is in contact with the elevated portion of Lada Terra to the W and with the lowland of Aino Planitia to the NE. The transitions of the mid-lands to the lowlands and highlands are, thus, one of the main themes of the geology within the V-57 quadrangle. The character of the transitions and distribution and sequence of units/structures in the midlands are crucially important in understanding the time and modes of formation of this topographic province. The most prominent features in the map area are linear deformational zones consisting of swarms of grooves and graben and large coronae. The zones characterize the central and NW portions of the map area and represent regionally important, broad (up to 100s km wide) ridges that are 100s m high. Relatively small (100s km across, 100s m deep) equidimensional basins occur between the corona-groove-chains in the west and border the central chain from the east. Here we describe units that make up the surface within the V-57 quadrangle and present a summary of our geological map that shows the areal distribution of the major groups of units.

Ivanov, M. A.↗

Proceedings of the 40th Lunar and Planetary Science Conference

The 40th Lunar and Planetary Science Conference included sessions on: Phoenix: Exploration of the Martian Arctic; Origin and Early Evolution of the Moon; Comet Wild 2: Mineralogy and More; Astrobiology: Meteorites, Microbes, Hydrous Habitats, and Irradiated Ices; Phoenix: Soil, Chemistry, and Habitability; Planetary Differentiation; Presolar Grains: Structures and Origins; SPECIAL SESSION: Venus Atmosphere: Venus Express and Future Missions; Mars Polar Caps: Past and Present; SPECIAL SESSION: Lunar Missions: Results from Kaguya, Chang'e-1, and Chandrayaan-1, Part I; 5 Early Nebula Processes and Models; SPECIAL SESSION: Icy Satellites of Jupiter and Saturn: Cosmic Gymnasts; Mars: Ground Ice and Climate Change; SPECIAL SESSION: Lunar Missions: Results from Kaguya, Chang'e-1, and Chandrayaan-1, Part II; Chondrite Parent-Body Processes; SPECIAL SESSION: Icy Satellites of Jupiter and Saturn: Salubrious Surfaces; SNC Meteorites; Ancient Martian Crust: Primary Mineralogy and Aqueous Alteration; SPECIAL SESSION: Messenger at Mercury: A Global Perspective on the Innermost Planet; CAIs and Chondrules: Records of Early Solar System Processes; Small Bodies: Shapes of Things to Come; Sulfur on Mars: Rocks, Soils, and Cycling Processes; Mercury: Evolution and Tectonics; Venus Geology, Volcanism, Tectonics, and Resurfacing; Asteroid-Meteorite Connections; Impacts I: Models and Experiments; Solar Wind and Genesis: Measurements and Interpretation; Mars: Aqueous Processes; Magmatic Volatiles and Eruptive Conditions of Lunar Basalts; Comparative Planetology; Interstellar Matter: Origins and Relationships; Impacts II: Craters and Ejecta Mars: Tectonics and Dynamics; Mars Analogs I: Geological; Exploring the Diversity of Lunar Lithologies with Sample Analyses and Remote Sensing; Chondrite Accretion and Early History; Science Instruments for the Mars Science Lander; . Martian Gullies: Morphology and Origins; Mars: Dunes, Dust, and Wind; Mars: Volcanism; Early Solar System Chronology; Seek Out and Explore: Upcoming and Future Missions; Mars: Early History and Impact Processes; Mars Analogs II: Chemical and Spectral; Achondrites and their Parent Bodies; and Planning for Future Exploration of the Moon The poster sessions were: Lunar Missions: Results from Kaguya, Chang'e-1, and Chandrayaan-1; LRO and LCROSS; Geophysical Analysis of the Lunar Surface and Interior; Remote Observation and Geologic Mapping of the Lunar Surface; Lunar Spectroscopy; Venus Geology, Geophysics, Mapping, and Sampling; Planetary Differentiation; Bunburra and Buzzard Coulee: Recent Meteorite Falls; Meteorites: Terrestrial History; CAIs and Chondrules: Records of Early Solar System Processes; Volatile and Organic Compounds in Chondrites; Crashing Chondrites: Impact, Shock, and Melting; Ureilite Studies; Petrology and Mineralogy of the SNC Meteorites; Martian Meteorites; Phoenix Landing Site: Perchlorate and Other Tasty Treats; Mars Polar Atmospheres and Climate Modeling; Mars Polar Investigations; Mars Near-Surface Ice; Mars: A Volatile-Rich Planet; Mars: Geochemistry and Alteration Processes; Martian Phyllosilicates: Identification, Formation, and Alteration; Astrobiology; Instrument Concepts, Systems, and Probes for Investigating Rocks and Regolith; Seeing is Believing: UV, VIS, IR, X- and Gamma-Ray Camera and Spectrometer Instruments; Up Close and Personal: In Situ Analysis with Laser-Induced Breakdown Spectroscopy and Mass Spectrometry; Jupiter and Inscrutable Io; Tantalizing Titan; Enigmatic Enceladus and Intriguing Iapetus; Icy Satellites: Cryptic Craters; Icy Satellites: Gelid Geology/Geophysics; Icy Satellites: Cool Chemistry and Spectacular Spectroscopy; Asteroids and Comets; Comet Wild 2: Mineralogy and More; Hypervelocity Impacts: Stardust Models, LDEF, and ISPE; Presolar Grains; Early Nebular Processes: Models and Isotopes; Solar Wind and Genesis: Measurements and Interpretation; Education and Public Outreach; Mercury; Pursuing Lunar Exploration; Sources and Eruptionf Lunar Basalts; Chemical and Physical Properties of the Lunar Regolith; Lunar Dust and Transient Surface Phenomena; Lunar Databases and Data Restoration; Meteoritic Samples of the Moon; Chondrites, Their Clasts, and Alteration; Achondrites: Primitive and Not So Primitive; Iron Meteorites; Meteorite Methodology; Antarctic Micrometeorites; HEDs and Vesta; Dust Formation and Transformation; Interstellar Organic Matter; Early Solar System Chronology; Comparative Planetology; Impacts I: Models and Experiments; Impacts II: Craters and Ejecta; Mars: Volcanism; Mars: Tectonics and Dynamics; Martian Stratigraphy: Understanding the Geologic History of Mars Through the Sedimentary Rock Record; Mars: Valleys and Valley Networks; Mars: Aqueous Processes in Valles Marineris and the Southern Highlands; Mars: Aqueous Geomorphology; Martian Gullies: Morphology and Origins; Mars: Dunes, Dust, and Wind; Mars: Remote Sensing; Mars: Geologic Mapping, Photogrammetry, and Cratering; Martian Mineralogy: Constraints from Missions and Laboratory Investigations; Mars Analogs: Chemical and Physical; Mars Analogs: Sulfates and Sulfides; Missions: Approaches, Architectures, Analogs, and Actualities; Not Just Skin Deep: Electron Microscopy, Heat Flow, Radar, and Seismology Instruments and Planetary Data Systems, Techniques, and Interpretation.

Source record↗

Stable isotopic studies of H,C,N,O and S in samples of Martian origin

The present day geochemical cycles of volatile elements through the various reservoirs on Earth are largely understood within the context of the planet's standing as a geologically and biologically evolved body. In terrestrial studies stable isotope measurements of light elements (H, C, N, O and S) can be utilized to obtain insight into the conditions prevailing during formation of rocks of various types. Perhaps the most important problem which could be addressed by light element studies of the sorts of specimen likely to be available from remote automatic sampling, would be the role of volatiles during evolution. Of fundamental importance here is the question of whether Mars was volatile rich or volatile poor. The only way to fully comprehend the effects of volatile cycling through the mantle crust and regolith atmosphere polar cap system of Mars, is by analyses of appropriate returned samples. In order to interpret the record of geological activity in Martian samples it will be necessary to understand how the past, or present, surface environment may have acted to disturb the primary characteristics of the rocks.

Wright, I. P.↗

Geologic Mapping of the Martian Impact Crater Tooting

Tooting crater is approximately 29 km in diameters, is located at 23.4 deg N, 207.5 deg E and is classified as a multi-layered ejecta crater. Tooting crater is a very young crater, with an estimated age of 700,000 to 2M years. The crater formed on virtually flat lava flows within Amazonis Planitia where there appears to have been no major topographic features prior to the impact, so that we can measure ejecta thickness and cavity volume. In the past 12 months, the authors have: published their first detailed analysis of the geometry of the crater cavity and the distribution of the ejecta layers; refined the geologic map of the interior of Tooting crater through mapping of the cavity at a scale of 1:1100K; and continued the analysis of an increasing number of high resolution images obtained by the CTX and HiRISE instruments. Currently the authors seek to resolve several science issues that have been identified during this mapping, including: what is the origin of the lobate flows on the NW and SW rims of the crater?; how did the ejecta curtain break apart during the formation of the crater, and how uniform was the emplacement process for the ejecta layers; and, can we infer physical characteristics about the ejecta? Future study plans include the completion of a draft geologic map of Tooting crater and submission of it to the U.S. Geological survey for a preliminary review, publishing a second research paper on the detailed geology of the crater cavity and the distribution of the flows on the crater rim, and completing the map text for the 1:100K geologic map description of units at Tooting crater.

Mouginis-Mark, Peter↗

The Geology of Inferno Chasm, Idaho: a Terrestrial Analog for Lunar Rilles?

Lunar sinuous rilles are thought to have formed by thermal erosion, mechanical erosion, construction, or a combination of these processes via emplacement by lava tubes or lava channels. The investigation of Hadley Rille by Apollo 15 provided the first field observations of a rille, but remote sensing observations remain our primary method for studying these features. Terrestrial volcanic features with similar morphologies to lunar rilles can provide insight into their formation on the Moon.

Geology↗

Remote sensing of some sedimentary rocks.

Sedimentary rocks including varying sized clastics and carbonates were overflown by aircraft between 1966 and 1971 producing data in the ultraviolet to microwave regions of the electromagnetic spectrum. This paper reports that multispectral analysis increases the ease and rapidity of discrimination of rock types having subtle differences in physical characteristics, but fails to enhance and may degrade distinctions where physical characteristics are significantly different. Brief resumes of color and color IR photographic data are presented. Thermal infrared is found to be useful in the mapping of rock units, but limitations such as moisture variation, soil cover, and vegetation may exceed in one formation the distinction between differing lithologies. A brief review of previously published SLAR data is included for completeness. Remote sensing techniques should reduce field geological effort by as much as 50%.

Brennan, P. A.↗

Wilson cycle studies

Continents originate by the sweeping together of island arcs. Continental and island arc crusts are dominated by rocks of comparable compositional and density ranges, evidence of the operation of this process is abundant in the geological record, and can be seen in action today in Indonesia. Lineaments within continents are attributable to a small number of processes of continent formation and modification, but interactions among these processes may produce complex patterns.

Source record↗

Glasses formed by hypervelocity impact

This paper presents description, classification, and geological setting of impact glasses, which are formed as a result of meteorite impacts with the planetary surface, and discusses the impact-glass formation process in the context of cratering mechanics. Impact glasses can be classified as belonging to two major groups: (1) mineral glasses, which are identical in composition to a mineral, and (2) rock glasses, which have the composition of a rock or a mixture of various rocks. Rock glasses may be (1) melt ejecta, (2) parts of a coherent melt layer inside the crater cavity, or (3) dikes or veins. The composition of rock glasses at a particular crater can be matched by that of the target. In nonporous rocks, the formation of rock glasses requires peak pressures in excess of 60-80 GPa, while mineral glasses are formed in the pressure range of about 25 to 55 GPa; in porous rocks, interstitial glass forms at pressures as low as 5 GPa.

Stoeffler, D.↗

Tectonic evolution of Eastern Ishtar Terra, Venus

Tectonic deformation is cited as the cause for the complex morphology and topography of Eastern Ishtar Terra. A number of models proposed to account for this deformation are reviewed, and their predictions for the geology of Fortuna Tessera are examined. The detailed geology, topography, and structural fabric of Eastern Ishtar are reviewed, and these observations are compared to the predictions of the existing models for the formation and evolution of Fortuna Tessera. On the basis of the analysis, a number of conclusions are drawn regarding the evolution of Eastern Ishtar Terra. These include the recognition of primary morphological and topographical patterns which allow Eastern Ishtar Terra to be divided into four major physiographic regions named Maxwell Montes, Eastern Fortuna Tessera, Central Fortuna Tessera, and Northern Fortuna Tessera. A model is suggested that accounts for the morphology and high topography of Eastern Ishtar Terra.

Vorder Bruegge, R. W.↗

Styles of crater gradation in Southern Ismenius Lacus, Mars: Clues from Meteor Crater, Arizona

Impact craters on the Earth and Mars provide a unique opportunity to quantify the gradational evolution of instantaneously created landforms in a variety of geologic settings. Unlike most landforms, the initial morphology associated with impact craters on both planets is uncomplicated by competition between construction and degradation during formation. Furthermore, pristine morphologies are both well-constrained and similar to a first order. The present study compares styles of graduation at Meteor Crater with those around selected craters (greater than 1-2 km in diameter) in southern Ismenius Lacus. Emphasis is placed on features visible in images near LANDSAT TM resolution (30-50 m/pixel) which is available for both areas. In contrast to Mars, vegetation on the Earth can modify gradation, but appears to influence overall rates and styles by 2X-3X rather than orders of magnitude. Further studies of additional craters in differing settings will refine the effects of this and other factors (e.g., substrate). Finally, by analogy with results from other terrestrial gradational surfaces this study should help provide constraints on climate over crater histories.

Grant, J. A.↗

Temporal changes in the geographic distribution, elevation, and potential origin of the Martian outflow channels

Observational evidence of outflow channel activity on Mars suggests that water was abundant in the planet's early crust. However, with the decline in the planet's internal heat flow, a freezing front developed within the regolith that propagated downward with time and acted as a thermodynamic sink for crustal H2O. One result of this thermal evolution is that, if the initial inventory of water on Mars was small, the cryosphere may have grown to the point where all the available water was taken up as ground ice. Alternatively, if the inventory of H2O exceeds the current pore volume of the cryosphere, then Mars has always possessed extensive bodies of subpermafrost groundwater. We have investigated the relative age, geographic distribution, elevation, and geologic setting of the outflow channels in an effort to accomplish the following: (1) identify possible modes of origin and evolutionary trends in their formation; (2) gain evidence regarding the duration and spatial distribution of groundwater in the crust; and (3) better constraint estimates of the planetary inventory of H2O.

Tribe, S.↗

Admittance Survey of Type 1 Coronae on Venus: Implications for Elastic Thickness

Coronae are volcano-tectonic features on Venus which range from 60km to 2600km and are defined by their nearly circular patterns of fractures. Type 1 (regular) coronae are classified as having >50% complete fracture annuli. Previous work has examined the factors controlling the morphology, size, and fracture pattern of coronae, using lithospheric properties, loading signature and geologic characteristics. However, these studies have been limited to Type 2 (topographic) coronae (e.g. coronaes with <50% fracture annuli), and the factors controlling the formation of Type 1 coronae remain poorly understood. In this study, we apply the methodology of to survey the admittance signature for Type 1 coronae to determine the controlling parameters which govern Type 1 coronae formation.

Hoogenboom, T.↗

The Eons of Chaos and Hades

We propose the Chaotian Eon to demarcate geologic time from the origin of the Solar System to the Moonforming impact on Earth. This separates the solar system wide processes of planet formation from the subsequent divergent evolution of the inner planets. We further propose the division of the Hadean Eon into eras and periods and naming the proto-Earth Tellus.

Goldblatt, C.↗

Precious Dust Two Mission Converge on Asteroid Sample Returns

Far-flung spacecraft deliver incredible views of distant worlds. But there's nothing like bringing samples back to Earth. Instruments carried by spacecraft have limitations-of power, complexity, size, and number. Their investigations leave many fundamental questions unanswered, questions that we might be able to answer if only we had samples. This summer marks the beginning of an exciting new era in sample-return missions: NASA's OSIRIS-REx spacecraft arrives at asteroid Bennu, and the Japanese Hayabusa2 spacecraft arrives at asteroid Ryugu. Both are primitive asteroids-dark remnants of Solar System formation that carry carbon and water-a type of asteroid that's never been visited before. After thoroughly mapping their respective asteroids for geology and mineralogy, each probe will collect surface samples and return them to Earth. I can't wait to study them in my laboratory. Cosmic-dust pioneer Kazu Tomeoka introduced me to the dream of sample-return missions 20 years ago. In those days, the only returned extraterrestrial samples were from the Moon. He said to his students, "In the near future, we will be able to collect samples from asteroids and comets. There will be no need to wait for meteorites or cosmic dust to come and fall from the sky. And some of you might be the first to look at those samples." This inspired my life's work: laboratory analysis of returned astromaterials.

Nakamura-Messenger, Keiko↗