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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Self-organized rock textures and multiring structure in the Duolun crater

The Duolun impact crater is a multiring basin located 200 km north of Beijing. From the center to the edge of the crater there are innermost rim, inner ring, outer rim, and outermost ring. Recently, we have found some self-organized textures or chaos phenomena in shock-metamorphic rocks from the Duolun impact crater, such as turbulence in matrices of impact glass, oscillatory zoning, or chemical chaos of spherulites in spherulitic splashed breccia, fractal wavy textures or self-similar wavy textures with varied scaling in impact glass, and crystallite beams shaped like Lorentz strange attractors. The rare phenomena indicate that the shock-metamorphic rocks from Duolun crater are formed far from equilibrium. If impact cratering generates momentarily under high-pressure and superhigh-temperature, occurrence of those chaos phenomena in shock-metamorphic rock is not surprising.

Wu, Siben↗
NASA NTRS1977

Impact cratering phenomenon for the Ries multiring structure based on constraints of geological, geophysical, and petrological studies and the nature of the impacting body

In the present paper, an attempt is made to delineate, on the basis of field and laboratory data, the phenomenon of formation of the Ries multiring basin - the best preserved very large terrestrial impact structure. The model proposed conforms to constraints imposed by geological, geophysical, and petrological studies and by the nature of the postulated impacting body. It is also based on the impact features of a stony meteorite measuring 3 km in diameter at an impact velocity of 15 km/sec. The schematic reconstruction shows that critical to the production of a shallow crater is shallow impact penetration (shallow depth of burst). This and the nonballistic ejection of excavated material appear to be genetically related, i.e., if extensive nonballistic transport is recognized, then the associated crater must be a shallow structure and vice versa. This also means the shallow configuration of a crater may not have anything to do with postcratering readjustment.

Chao, E. C. T.↗
NASA NTRS1992

Variation in multiring basic structures as a function of impact angle

Previous studies have demonstrated that the impact process in the laboratory varies as a function of impact angle. This variation is attributed to changes in energy partitioning and projectile failure during the impact and, in simple craters, produces a sequence of progressively smaller and more asymmetric crater forms as impact angle decreases from approximately 20 degrees. Variations in impact angle can produce differences in the appearance of multiring impact basins. Comparisons of Orientale to the more oblique impact structure at Crisium also suggests that these differences primarily reflect the degree of cavity collapse. The relative changes in massif ring topography, basin scarp relief, and the distribution of peripheral mare units are consistent with a reduction in degree of cavity collapse with decreasing impact angle. The prominent uprange basin scarps and the restriction of tectonically derived peripheral mare units along uprange ring structures also may indicate an uprange enhancement of failure during cavity collapse. Finally, although basin ring faults appear to be preferred pathways for mare volcanism, fault-controlled peripheral mare volcanism occurs most readily uprange of an oblique impact; elsewhere such volcanism apparently requires superposition of an impact structure on the ring fault.

Wichman, R. W.↗
NASA NTRS1996

The Lunar Crust: Global Structure and Signature of Major Basins

New lunar gravity and topography data from the Clementine Mission provide a global Bouguer anomaly map corrected for the gravitational attraction of mare fill in mascon basins. Most of the gravity signal remaining after corrections for the attraction of topography and mare fill can be attributed to variations in depth to the lunar Moho and therefore crustal thickness. The large range of global crustal thickness (approx. 20-120 km) is indicative of major spatial variations in melting of the lunar exterior and/or significant impact-related redistribution. The 6l-km average crustal thickness, constrained by a depth-to-Moho measured during the Apollo 12 and 14 missions, is preferentially distributed toward the farside, accounting for much of the offset in center-of-figure from the center-of-mass. While the average farside thickness is 12 km greater than the nearside, the distribution is nonuniform, with dramatic thinning beneath the farside, South Pole-Aitken basin. With the global crustal thickness map as a constraint, regional inversions of gravity and topography resolve the crustal structure of major mascon basins to half wavelengths of 150 km. In order to yield crustal thickness maps with the maximum horizontal resolution permitted by the data, the downward continuation of the Bouguer gravity is stabilized by a three- dimensional, minimum-slope and curvature algorithm. Both mare and non-mare basins are characterized by a central upwarped moho that is surrounded by rings of thickened crust lying mainly within the basin rims. The inferred relief at this density interface suggests a deep structural component to the surficial features of multiring lunar impact basins. For large (greater than 300 km diameter) basins, moho relief appears uncorrelated with diameter, but is negatively correlated with basin age. In several cases, it appears that the multiring structures were out of isostatic equilibrium prior to mare emplacement, suggesting that the lithosphere was strong enough to maintain their state of stress to the present.

Neumann, Gregory A.↗
NASA NTRS2017

Large Impact Features on Icy Galilean Satellites

Impact crater morphology can be a very useful tool for probing planetary interiors, but nowhere in the solar system is a greater variety of crater morphologies observed (Fig. 1) than on the large icy Galilean satellites Ganymede and Callisto [e.g., 1- 3]. As on the rocky terrestrial planets, impact crater morphology becomes more complex with increasing size on these satellites. With increasing size, however, these same craters become less like their counterparts on the rocky planets. Several impact landforms and structures (multiring furrows, palimpsests, and central domes, for example), have no obvious analogs on any other planets. Further, several studies [e.g., 4-6] have drawn attention to impact landforms on Europa which are unusual, even by Galilean satellite standards. These radical differences in morphology suggest that impact into icy lithospheres that are mechanically distinct from silicate lithospheres may be responsible. As such, large impact structures may be important probes of the interiors of these bodies over time [e.g., 7]. The first goal of this work is to integrate and correlate the detailed morphologic and morphometric measurements and observations of craters on icy Galilean satellites [e.g., 4, 8-12] with new detailed mapping of these structures from Galileo high-resolution images. As a result, we put forward a revised crater taxonomy for Ganymede and Callisto in order to simplify the nonuniform impact crater nomenclature cluttering the literature. We develop and present an integrated model for the development of these unusual crater morphologies and their implications for the thermal evolution of these bodies.

crater morphologies↗
NASA NTRS2001

Geology of Lofn Crater, Callisto

Lofn crater is a 180-km-diameter impact structure in the southern cratered plains of Callisto and is among the youngest features seen on the surface. The Lofn area was imaged by the Galileo spacecraft at regional-scale resolutions (875 m/pixel), which enable the general geology to be investigated. The morphology of Lofn crater suggests that (1) it is a class of impact structure intermediate between complex craters and palimpsests or (2) it formed by the impact of a projectile which fragmented before reaching the surface, resulting in a shallow crater (even for Callisto). The asymmetric pattern of the rim and ejecta deposits suggests that the impactor entered at a low angle from the northwest. The albedo and other characteristics of the ejecta deposits from Lofn also provide insight into the properties of the icy lithosphere and subsurface configuration at the time of impact. The "target" for the Lofn impact is inferred to have included layered materials associated with the Adlinda multiring structure northwest of Loh and ejecta deposits from the Heimdall crater area to the southeast. The Lofn impact might have penetrated through these materials into a viscous substrate of ductile ice or possibly liquid water. This interpretation is consistent with models of the current interior of Callisto based on geophysical information obtained from the Galileo spacecraft.

Greeley, Ronald↗
NASA NTRS1971

Mariner Mars 1969 - Atmospheric results

Mars atmospheric data from Mariner flights, discussing north polar haze, bright surface features morphology, multiring structures and water vapor exchange

Leighton, R. B.↗
NASA NTRS1979

Charting the southern seas - The evolution of the lunar Mare Australe

Mare Australe has been subjected to at least four major episodes of basalt eruption ranging in age from early Imbrian to Eratosthenian. The basalts were emplaced largely in flood eruptions from at least 197 vents located on post-basin impact crater floors. The youngest basalts occur in an annulus near the outer edge of the basin. The fill thickness apparently reflects a multiring structure for the post-impact morphology of the Australe basin; the thin basaltic fill was not sufficient a load to produce tectonic rilles, but mare ridges are present and exhibit a prominent north-south alignment.

Whitford-Stark, J. L.↗
NASA NTRS1982

Craters and basins on Ganymede and Callisto - Morphological indicators of crustal evolution

The morphologic characteristics of craters and palimpsests on Ganymede and Callisto are surveyed, and the crustal properties of these satellites and the evolution of the properties are studied. The morphology of bowl-shaped craters, smooth-floored craters, craters without central peaks, craters with central pits, chain craters on Callisto, the Gilgamesh and Western Equatorial Basins on Ganymede, crater palimpsests and penepalimpsests, multiring structures on Callisto, and the Galileo Regio rimmed furrow system on Ganymede are described individually. The crustal evolution is addressed by examining the development of the Galileo Regio system, the distribution of crater retention ages, the record of ray clusters, the thermal history of the lithosphere of Ganymede, and the origin of the central pits. It is suggested that as the lithosphere of each satellite cooled and thickened, crater retentivity spread as a wave from the polar regions and the antapex toward the apex; at any given location, progressively larger craters were retained with the passage of time.

Passey, Q. R.↗
NASA NTRS1985

Tectonics of the Galileo Regio on Ganymede

The surface of Ganymede consists of dark cratered terrain, and groved terrain. The dark cratered terrains form polygonal units, the largest of which is Galileo Regio, the surface of which is transected by furrows, smooth floored valleys bounded by relatively sharp parallel ridges. The most apparent of them are grouped together and form an apparently arcuate system of subparallel furrows which was mapped using Voyager pictures and plotted on a map using a stereographic projection. With this kind of projection, the main furrow system is not arcuate, but rectilinear. Observations strongly suggest that the Galileo Regio furrow systems are not of impact origin and appear to be irrelevant to discussions about the basins' morphology or evolution of planetary lithosphere determined from multiring structures.

Thomas, P. G.↗
NASA NTRS1992

New multirate sampled-data control law structure and synthesis algorithm

A new multirate sampled-data control law structure is defined and a new parameter-optimization-based synthesis algorithm for that structure is introduced. The synthesis algorithm can be applied to multirate, multiple-input/multiple-output, sampled-data control laws having a prescribed dynamic order and structure, and a priori specified sampling/update rates for all sensors, processor states, and control inputs. The synthesis algorithm is applied to design two-input, two-output tip position controllers of various dynamic orders for a sixth-order, two-link robot arm model.

Berg, Martin C.↗
NASA NTRS1991

A new multirate sampled-data control law structure and synthesis algorithm

A new multirate sampled-data control law structure is defined and a new parameter-optimization-based synthesis algorithm for that structure is introduced. The synthesis algorithm can be applied to multirate, multiple-input multiple-output, sampled-data control laws having a prescribed dynamic order and structure, and a priori specified sampling/update rates for all sensors, processor states, and control inputs. The synthesis algorithm is applied to design two-input, two-output tip position controllers of various dynamic orders for a sixth-order, two-link robot arm model.

Berg, Martin C.↗
NASA NTRS1977

Cratering motions and structural deformation in the rim of the Prairie Flat multiring explosion crater

Cratering motions and structural deformation are described for the rim of the Prairie Flat multiring crater, 85.5 m across and 5.3 m deep, which was formed by the detonation of a 500-ton TNT surface-tangent sphere. The terminal displacement and motion data are derived from marker cans and velocity gages emplaced in drill holes in a three-dimensional matrix radial to the crater. The integration of this data with a detailed geologic cross section, mapped from deep trench excavations through the rim, provides a composite view of the general sequence of motions that formed a transiently uplifted rim, overturned flap, inverted stratigraphy, downfolded rim, and deformed strata in the crater walls. Preliminary comparisons with laboratory experimental cratering and with numerical simulations indicate that explosion craters of the Prairie Flat-type generated by surface and near-surface energy sources tend to follow predictable motion sequences and produce comparable structural deformation. More specifically, central uplift and multiring impact craters with morphologies and structures comparable to Prairie Flat are inferred to have experienced similar deformational histories of the rim, such as uplift, overturning, terracing, and downfolding.

Roddy, D. J.↗
NASA NTRS1995

Volcanic Constructs on Ganymede and Enceladus: Topographic Evidence from Stereo Images and Photoclinometry

The morphology of volcanic features on Ganymede differs significantly from that on the terrestrial planets. Few if any major volcanic landforms, such as thick flows or shield volcanoes, have been identified to date. Using new stereo Voyager images, we have searched Ganymede for relief-generating volcanic constructs. We observed seven major types of volcanic structures, including several not previously recognized. The oldest are broad flat-topped domes partially filling many older craters in dark terrain. Similar domes occur on Enceladus. Together with smooth dark deposits, these domes indicate that the volcanic history of the dark terrain is complex. Bright terrain covers vast areas, although the style of emplacement remains unclear. Smooth bright materials embay and flood older terrains, and may have been emplaced as low- viscosity fluids. Associated with smooth bright material are a number of scalloped-shaped, semi- enclosed scarps that cut into preexisting terrain. In planform these structures resemble terrestrial calderas. The youngest volcanic materials identified are a series of small flows that may have flooded the floor of the multiring impact structure Gilgamesh, forming a broad dome, The identification of volcanic constructs up to I km thick is the first evidence for extrusion of moderate-to-high viscosity material on Ganymede. Viscosity and yield strength estimates for these materials span several orders of magnitude, indicating that volcanic materials on Ganymede have a range of compositions and/or were extruded under a wide range of conditions and/or eruptive styles.

Schenk, Paul M.↗
NASA NTRS1981

The excavation stage of basin formation - A qualitative model

One of the most complex problems in planetary geology and geophysics is the determination of the nature of the impact cratering processes at scales of tens to thousands of kilometers that produce the complex morphological structures of multiring basins. The cratering process is frequently considered to be divided into three stages, including a short high-pressure stage of initial contact between the projectile and the planetary crust, a longer excavation or cratering flow stage culminating in the formation of a transient crater, and a still longer modification stage during which the transient crater is modified into the observed final geologic form. The transient crater may be considered as the initial boundary condition of the modification stage. In the present investigation, the nature of the transient crater is indicated by the cratering flow field determined from numerical simulations of the excavation stage. Attention is given to empirical and theoretical scaling.

Croft, S. K.↗
NASA NTRS1987

Cleopatra Patera on Venus - Venera 15/16 evidence for a volcanic origin

The nonconcentric nature, anomalous depth, and terraced morphology of the nested craters that compose Cleopatra Patera are more closely analogous to volcanic craters (calderas) than multiring impact structures. Associated deposits northeast and downslope of the Patera first recognized on Venera 15/16 radar images are interpreted as volcanic plains related to, and perhaps cogenetic with, Cleopatra. The plains lavas probably originated as effusions from a radial rift zone or ring fissures. Rim deposits surrounding Cleopatra are asymmetric along the structural fabric of the region, also indicating fissure-type eruptions. Finally, a volcanic origin not only is easily reconciled with the tectonic setting of the Patera, it is almost required by the correlation between the Patera and regional structural trend.

Schaber, Gerald G.↗
NASA NTRS1991

Progress in multirate digital control system design

A new methodology for multirate sampled-data control design based on a new generalized control law structure, two new parameter-optimization-based control law synthesis methods, and a new singular-value-based robustness analysis method are described. The control law structure can represent multirate sampled-data control laws of arbitrary structure and dynamic order, with arbitrarily prescribed sampling rates for all sensors and update rates for all processor states and actuators. The two control law synthesis methods employ numerical optimization to determine values for the control law parameters. The robustness analysis method is based on the multivariable Nyquist criterion applied to the loop transfer function for the sampling period equal to the period of repetition of the system's complete sampling/update schedule. The complete methodology is demonstrated by application to the design of a combination yaw damper and modal suppression system for a commercial aircraft.

Berg, Martin C.↗