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At least 343 records · Page 19Linked to original sources
USGS2018

Interoperability in planetary research for geospatial data analysis

For more than a decade there has been a push in the planetary science community to support interoperable methods for accessing and working with geospatial data. Common geospatial data products for planetary research include image mosaics, digital elevation or terrain models, geologic maps, geographic location databases (e.g., craters, volcanoes) or any data that can be tied to the surface of a planetary body (including moons, comets or asteroids). Several U.S. and international cartographic research institutions have converged on mapping standards that embrace standardized geospatial image formats, geologic mapping conventions, U.S. Federal Geographic Data Committee (FGDC) cartographic and metadata standards, and notably on-line mapping services as defined by the Open Geospatial Consortium (OGC). The latter includes defined standards such as the OGC Web Mapping Services (simple image maps), Web Map Tile Services (cached image tiles), Web Feature Services (feature streaming), Web Coverage Services (rich scientific data streaming), and Catalog Services for the Web (data searching and discoverability). While these standards were developed for application to Earth-based data, they can be just as valuable for planetary domain. Another initiative, called VESPA (Virtual European Solar and Planetary Access), will marry several of the above geoscience standards and astronomy-based standards as defined by International Virtual Observatory Alliance (IVOA). This work outlines the current state of interoperability initiatives in use or in the process of being researched within the planetary geospatial community.

Planetary and Space Science↗
USGS2019

The compositions of the lunar crust and upper mantle: Spectral analysis of the inner rings of lunar impact basins

The innermost ring in impact basins exposes material originating from various depths, and can be used to study the composition of the lunar crust with depth. In this study, we conduct quantitative mineralogical analyses of the innermost ring in 13 lunar impact basins using reflectance data from the Kaguya Multiband Imager and radiative transfer modeling. We use results from recent hydrocode modeling to calculate the depth of origin of the material exposed by the innermost rings. We find that the most abundant rock type on the innermost ring of most basins is anorthosite. The mafic assemblages are dominated by olivine in some cases, but most often by pyroxene. The impact modeling suggests that the innermost ring material was excavated from a wide range of depths. Here we focus on two mean depths: a crustal component and a mantle component. The crustal component largely dominates the innermost ring material, and the mantle component is present on the innermost ring of 9 of the basins we studied. On these 9 rings, the abundance of low-calcium pyroxene decreases with the proportion of crustal component, suggesting a dominantly mantle origin. However, as we do not detect exposures of ultramafic material, such mantle material is possibly present at the sub-pixel scale (<62 m). This quantitative study reassesses the composition of the lunar crust and upper mantle, which is of great importance for understanding the formation of the Moon.

Planetary and Space Science↗
USGS2003

Compositional analyses of lunar pyroclastic deposits

The 5-band Clementine UVVIS data at ∼100 m/pixel were used to examine the compositions of 75 large and small lunar pyroclastic deposits (LPDs), and these were compared to representative lunar maria and highlands deposits. Results show that the albedo, spectral color, and inferred composition of most LPDs are similar to those of low-titanium, mature lunar maria. These LPDs may have consisted largely of fragmented basalt, with substantial components of iron-bearing mafic minerals (pyroxenes, olivine) and smaller amounts (if any) of volcanic glass. Several smaller LPDs also show substantial highland components. Three classes of very large deposits can be distinguished from most LPDs and from each other on the basis of crystallinity and possible titanium content of their pyroclastic components. One class has spectral properties that are dominated by high-titanium, crystallized “black beads” (e.g., Taurus–Littrow), a second consists of a mixture of high-titanium glasses and beads with a higher glass/bead ratio (Sulpicius Gallus) than that of Taurus–Littrow, and a third has a significant component of quenched iron-bearing volcanic glasses (Aristarchus) with possible moderate titanium contents. Although areally extensive, these three classes of very large pyroclastic deposits compose only 20 of the 75 deposits studied (∼27%), and eruption of such materials was thus likely to have been less frequent on the Moon.

Icarus↗
USGS2000

Compositional analyses of small lunar pyroclastic deposits using Clementine multispectral data

Clementine ultraviolet-visible (UVVIS) data are used to examine the compositions of 18 pyroclastic deposits (15 small, three large) at 13 sites on the Moon. Compositional variations among pyroclastic deposits largely result from differing amounts of new basaltic (or juvenile) material and reworked local material entrained in their ejecta upon eruption. Characterization of pyroclastic deposit compositions allows us to understand the mechanisms of lunar explosive volcanism. Evidence for compositional differences between small pyroclastic deposits at a single site is observed at Atlas crater. At all sites, compositional variation among the small pyroclastic deposits is consistent with earlier classification based on Earth-based spectra: three compositional groups can be observed, and the trend of increasing mafic absorption band strength from Group 1 to Group 2 to Group 3 is noted. As redefined here, Group 1 deposits include those of Alphonsus West, Alphonsus Southeast, Alphonsus Northeast 2, Atlas South, Crüger, Franklin, Grimaldi, Lavoisier, Oppenheimer, Orientale, and Riccioli. Group 1 deposits resemble lunar highlands, with weak mafic bands and relatively high UV/VIS ratios. Group 2 deposits include those of Alphonsus Northeast 1, Atlas North, Eastern Frigoris East and West, and Aristarchus Plateau; Group 2 deposits are similar to mature lunar maria, with moderate mafic band depths and intermediate UV/VIS ratios. The single Group 3 deposit, J. Herschel, has a relatively strong mafic band and a low UV/VIS ratio, and olivine is a likely juvenile component. Two of the deposits in these groups, Orientale and Aristarchus, are large pyroclastic deposits. The third large pyroclastic deposit, Apollo 17/Taurus Littrow, has a very weak mafic band and a high UV/VIS ratio and it does not belong to any of the compositional groups for small pyroclastic deposits. The observed compositional variations indicate that highland and mare materials are also present in many large and small pyroclastic deposits, and they suggest that volcanic glasses or spheres may not be dominant juvenile components in all large pyroclastic deposits.

Journal of Geophysical Research E: Planets↗
USGS2001

Rock types of South Pole-Aitken basin and extent of basaltic volcanism

The enormous pre-Nectarian South Pole-Aitken (SPA) basin represents a geophysically and compositionally unique region on the Moon. We present and analyze the mineralogical diversity across this basin and discuss the implications for basin evolution. Rock types are derived from Clementine multispectral data based on diagnostic characteristics of ferrous absorptions in fresh materials. Individual areas are characterized as noritic (dominated by low-Ca pyroxene), gabbroic/basaltic (dominated by high-Ca pyroxene), feldspathic (<3-6% FeO), and olivine-gabbro (dominated by high-Ca pyroxene and olivine). The anorthositic crust has effectively been removed from the interior of the basin. The style of volcanism within the basin extends over several 100 Myr and includes mare basalt and pyroclastic deposits. Several areas of ancient (pre-Orientale) volcanism, or cryptomaria, have also been identified. The nonmare mafic lithology that occurs across the basin is shown to be noritic in composition and is pervasive laterally and vertically. We interpret this to represent impact melt/breccia deposits derived from the lower crust. A few localized areas are identified within the basin that contain more diverse lithologies (gabbro, olivine-gabbro), some of which may represent material from the deepest part of the lower crust and perhaps uppermost mantle involved in the SPA event.

Journal of Geophysical Research E: Planets↗
USGS2009

Discovery of lake-effect clouds on Titan

Images from instruments on Cassini as well as from telescopes on the ground reveal the presence of sporadic small-scale cloud activity in the cold late-winter north polar region of Saturn's large moon Titan. These clouds lie underneath the previously discovered uniform polar cloud attributed to a quiescent ethane cloud at ???40 km and appear confined to the same latitudes as those of the largest known hydrocarbon lakes at the north pole of Titan. The physical properties of these clouds suggest that they are due to methane convection and condensation. Such convection could be caused by a process in some ways analogous to terrestrial lake-effect clouds. The lakes on Titan could be a key connection between the surface and the meteorological cycle. ?? 2009 by the American Geophysical Union.

Geophysical Research Letters↗
USGS2009

Photometric changes on Saturn's Titan: Evidence for active cryovolcanism

We report infrared spectrophotometric variability on the surface of Saturn's moon Titan detected in images returned by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini Saturn Orbiter. The changes were observed at 7°S, 138°W and occurred between October 27, 2005 and January 15, 2006. After that date the surface was unchanged until the most recent observation, March 18, 2006. We previously reported spectrophotometric variability at another location (26°S, 78°W). Cassini Synthetic Aperture RADAR (SAR) images find that the surface morphology at both locations is consistent with surface flows possibly resulting from cryovolcanic activity (Wall et al., companion paper, this issue). The VIMS‐reported time variability and SAR morphology results suggest that Titan currently exhibits intermittent surface changes consistent with present ongoing surface processes. We suggest that these processes involve material from Titan's interior being extruded or effused and deposited on the surface, as might be expected from cryovolcanism.

Geophysical Research Letters↗
USGS2011

Transient and steady state creep response of ice I and magnesium sulfate hydrate eutectic aggregates

Using uniaxial compression creep experiments, we characterized the transient and steady state deformation behaviors of eutectic aggregates of system ice I and MgSO4 11H2O (MS11; meridianiite), which has significance because of its likely presence on moons of the outer solar system. Synthetic samples of eutectic liquid bulk composition, which produce eutectic colonies containing 0.35-0.50 volume fraction MS11, were tested as functions of colony size and lamellar spacing, temperature (230-250 K), and confining pressure (0.1 and 50 MPa) to strains ???0.2. Up to a differential stress of 6 MPa, the ice I-MS11 aggregates display an order of magnitude higher effective viscosity and higher stress sensitivity than do aggregates of pure polycrystalline ice at the same conditions. The creep data and associated microstructural observations demonstrate, however, that the aggregates are additionally more brittle than pure ice, approaching rate-independent plasticity that includes rupture of the hydrate phase at 6-8 MPa, depending on the scale of the microstructure. Microstructures of deformed samples reveal forms of semibrittle flow in which the hydrate phase fractures while the ice phase deforms plastically. Semibrittle flow in the icy shell of a planetary body would truncate the lithospheric strength envelope and thereby decrease the depth to the brittle-ductile transition by 55% and reduce the failure limit for compressional surface features from 10 to ???6 MPa. A constitutive equation that includes eutectic colony boundary sliding and intracolony flow is used to describe the steady state rheology of the eutectic aggregates. Copyright ?? 2011 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗
USGS2011

M3 spectral analysis of lunar swirls and the link between optical maturation and surface hydroxyl formation at magnetic anomalies

We examined the lunar swirls using data from the Moon Mineralogy Mapper (M 3 ). The improved spectral and spatial resolution of M 3 over previous spectral imaging data facilitates distinction of subtle spectral differences, and provides new information about the nature of these enigmatic features. We characterized spectral features of the swirls, interswirl regions (dark lanes), and surrounding terrain for each of three focus regions: Reiner Gamma, Gerasimovich, and Mare Ingenii. We used Principle Component Analysis to identify spectrally distinct surfaces at each focus region, and characterize the spectral features that distinguish them. We compared spectra from small, recent impact craters with the mature soils into which they penetrated to examine differences in maturation trends on- and off-swirl. Fresh, on-swirl crater spectra are higher albedo, exhibit a wider range in albedos and have well-preserved mafic absorption features compared with fresh off-swirl craters. Albedoand mafic absorptions are still evident in undisturbed, on-swirl surface soils, suggesting the maturation process is retarded. The spectral continuum is more concave compared with off-swirl spectra; a result of the limited spectral reddening being mostly constrained to wavelengths less than ∼1500 nm. Off-swirl spectra show very little reddening or change in continuum shape across the entire M 3 spectral range. Off-swirl spectra are dark, have attenuated absorption features, and the narrow range in off-swirl albedos suggests off-swirl regions mature rapidly. Spectral parameter maps depicting the relative OH surface abundance for each of our three swirl focus regions were created using the depth of the hydroxyl absorption feature at 2.82 μ m. For each of the studied regions, the 2.82 μ m absorption feature is significantly weaker on-swirl than off-swirl, indicating the swirls are depleted in OH relative to their surroundings. The spectral characteristics of the swirls and adjacent terrains from all three focus regions support the hypothesis that the magnetic anomalies deflect solar wind ions away from the swirls and onto off-swirl surfaces. Nanophase iron (npFe 0 ) is largely responsible for the spectral characteristics we attribute to space weathering and maturation, and is created by vaporization/deposition by micrometeorite impacts and sputtering/reduction by solar wind ions. On the swirls, the decreased proton flux slows the spectral effects of space weathering (relative to nonswirl regions) by limiting the npFe 0 production mechanism almost exclusively to micrometeoroid impact vaporization/deposition. Immediately adjacent to the swirls, maturation is accelerated by the increased flux of protons deflected from the swirls.

Journal of Geophysical Research E: Planets↗
USGS2016

Planetary caves’ role in astronaut bases and the search for life

Planetary caves are practically everywhere. Scientists have identified more than 200 lunar and more than 2000 Martian cave-related features. They’ve also found vents and fissures associated with water ice plumes on Saturnian, Jovian, and Neptunian moons. Recently, primary vents of two possible cryovolcanoes were identified on Pluto.

Eos, Earth and Space Science News↗
USGS2018

A new Enceladus global control network, image mosaic, and updated pointing kernels from Cassini's thirteen-year mission

NASA's Cassini spacecraft spent 13 years exploring the Saturn system, including 23 targeted flybys of the small, geologically active moon Enceladus. These flybys provided a wealth of image data from Cassini's Imaging Science Subsystem. To improve the usability of the Enceladus data set, we created a new, global photogrammetric control network for Enceladus that enabled compilation of a versatile cartographic package to support geologic mapping and other investigations. The network used 586 images in four image filters with a pixel scale generally between 50 and 500 m per pixel and a phase angle less than 120° and consisted of 10,362 tie points and 173,704 individual image measures, averaging nearly 17 measures per tie point. Least squares bundle adjustment resulted in a root‐mean‐square residual of 0.45 pixel, corresponding to root‐mean‐square ground point uncertainties of 66, 51, and 46 m in latitude, longitude, and radius, respectively. Using our geodetic control network, we created new global image mosaics, coregistered flyby mosaics to support geologic mapping, and updated pointing kernels for every image used in the solution. These products, including the updated pointing kernels, are available to the community through NASA's Planetary Data System Imaging Annex. The bundle adjustment solution also yielded independently determined shape information, resulting in radii within the stated uncertainty of International Astronomical Union values. The challenges of the data set, and the technical methodology described here are applicable to bodies imaged during multiple flybys with variable viewing and illumination geometry, including other midsized satellites of Saturn, and the Europa Clipper mission.

Earth and Space Science↗
USGS2025

The pre-maria geologic history of the Imbrium basin preserved by remnant highlands massifs

The Imbrium basin is one of the largest and youngest impact basins on the Moon. It has experienced multiple phases of volcanism that filled the basin with basaltic lavas, obscuring most evidence of geologic activity prior to the emplacement of mare basalts. Elevated basin ring massifs, however, can retain some of that history due to their higher topographic elevation compared to the maria. In this work, we use thermal infrared and radar data sets in conjunction with compositional data sets to establish the presence of external material that has been deposited on top of several remnant basin massifs of Imbrium. These massifs originally formed as part of the Imbrium basin ring structure, but their material properties indicate that they have since experienced modification from outside sources. In southwest Imbrium, we present evidence that Mons Vinogradov was mantled by rock-poor, glassy pyroclastic material prior to the deposition of Eratosthenian-era basalts immediately surrounding the mons. In northern Imbrium, we find that Montes Recti and Montes Teneriffe were not affected by pyroclastic volcanism but rather were mantled by rock- and glass-poor ejecta materials likely related to the Iridum basin impact. At Mons Piton in eastern Imbrium, we see weaker glass signatures than those found at Mons Vinogradov, which we suggest could be due to a thin layer of reworked or partially buried glassy pyroclastic material. These results indicate that basin ring massifs provide a mechanism for studying the geologic history of lunar impact basins.

JGR Planets↗
USGS2012

Implications of the Surveyor 7 results

The chemical and television data from the Surveyor 7 mission are discussed. The significance of the α-scattering analysis is found to depend on whether the flow unit underlying the spacecraft was laid down by mass flow at the time of the Tycho-forming impact. The chemical composition of the site is significantly lower in Fe than the composition of the previously analyzed mare sites; no other resolvable distinctions can be made. The higher albedo of the highlands is attributed to the lower iron content in the silicate minerals. By assigning the atomic composition to minerals common in basaltic rocks, we estimate-the highland rock density to be 3.0 and the mare density to be 3.2. The densities may be incorporated into a discussion of recent information on the gravitational field of the moon, yielding estimates of crustal thickness in the highlands around 30 to 50 km. A number of television pictures of rocks and fragments are shown, and we offer some suggestions about the type and origin of these objects. They compose a heterogeneous population in which the brighter rocks seem to be more resistant to mechanical breakdown than the dark rocks. The characteristics of the fine-grained component of the surface mantle are found to be similar to those at earlier Surveyor sites. The process of eroding exposed rocks and covering them with a blanket of fine particles appears to be relatively less advanced than at the sites previously studied; A bright line of light was seen on the western horizon after sunset, as was observed during Surveyor 5 and 6; this rather puzzling phenomenon is discussed again.

Journal of Geophysical Research↗
USGS2012

Observations of the lunar regolith and the Earth from the television camera on Surveyor 7

Surveyor 7, the last spacecraft of the Surveyor series, landed about 30 km north of the rim crest of Tycho, one of the most prominent and well-known features in the southern part of the moon. About 21,000 pictures were transmitted during two lunar days of operation. At the Surveyor 7 site, the cumulative size-frequency distribution of craters 13 cm to 3 meters in diameter follows closely the distribution of craters observed at the other Surveyor sites in the lunar maria. This distribution of small craters is believed to be a steady-state distribution.

Journal of Geophysical Research↗
USGS2012

Lu-Hf constraints on the evolution of lunar basalts

Very low Ti basalts and green glass samples from the moon show high Lu/Hf ratios and low Hf concentrations. Low-Ti lunar basalts show high and variable Lu/Hf ratios and higher Hf concentrations, whereas high-Ti lunar basalts show low Lu/Hf ratios and high Hf concentrations. KREEP basalts have constant Lu/Hf ratios and high but variable Hf concentrations. Using the Lu-Hf behavior as a constraint, we propose a model for the mare basalts evolution. This constraint requires extensive crystallization of the primary lunar magma ocean prior to formation of the lunar mare basalt sources and the KREEP basalts. Mare basalts are produced by the melting of the cumulate rocks, and KREEP basalts represent the residual liquid of the magma ocean. Lu and Hf concentrations and the Hf isotopic data of lunar rocks suggest that assimilation cannot be accepted as a major process to explain the diversity of the lunar mare basalts. The urKREEP hypothesis is also unnecessary. Both high- and low-Ti basalts show enough iron enrichment to be regarded as melting products of the last stage cumulate rocks from the lunar magma ocean. The KREEP basalts are also rich in iron and may be regarded as the final, residual liquid left after the crystallization of the major portion of the primary lunar magma ocean.

Journal of Geophysical Research Solid Earth↗
USGS2012

Friction of ice

The frictional strength of ice seems to be well below that for all other rocks. Triaxial testing of cylinders of pure water ice containing a 45° inclined sawcut, at temperatures of 77 ≤ T ≤ 115 K and confining pressures 0.1 ≤ P ≤ 250 MPa, reveals the frictional laws τ = 0.20 σ n + 8.3 MPa for P ≥ 10 MPa and τ = 0.55 σ n + 1.0 MPa for P ≤ 5 MPa, where τ and σ n are the shear and normal stresses on the sawcut surface. Friction is independent of T and, over the one order of magnitude tested, of average sliding velocity. The sliding behavior is invariably stick slip. Examination of sliding surfaces shows only minor gouge development. A curious arrangement of densely packed short vertical fractures occurs primarily in samples with anomalously low strength. These results apply to models of near‐surface tectonic activity on Jupiter's three large icy moons, Europa, Callisto, and Ganymede. They indicate, for example, that a global expansion on Ganymede of 3 linear percent will cause extensional movement on preexisting faults at depths to 7±3 km.

Journal of Geophysical Research B: Solid Earth↗
USGS2010

The geology of the terrestrial planets.

During the last four years our knowledge of the geology of the terrestrial planets has advanced rapidly. The advances are particularly noticeable for Venus and Mars. Improved understanding of Venus has come largely from the Pioneer Venus mission. The period was also one of almost continuous data gathering for Mars as the Viking orbiters and landers, emplaced at the planet in 1976, continued to function. The last orbiter ran out of attitude- control gas in August of 1980 by which time about 55 000 pictures and vast amounts of infrared data had been collected. One lander continues to function and is expected to do so for several years. Only modest advances were made in the cases of Moon and Mercury, however, for little new data was acquired. -from Author

Reviews of Geophysics and Space Physics↗
USGS1970

Lunar radar mapping: Correlation between radar reflectivity and stratigraphy in north-western mare imbrium

DELAY-DOPPLER radar maps of the Moon obtained with the 430 MHz (70 cm wavelength) radar of the Arecibo Ionospheric Observatory in Puerto Rico (Thompson, unpublished) are at present being studied to correlate geological information with the radar reflexion characteristics of the lunar surface. Preliminary evaluation of the radar data for the Sinus Iridum quadrangle (32°–48° N; 14°–38° W) has revealed that the lowest values of radar reflectivity are closely correlated with the mare materials of lowest albedo mapped by Schaber 1 as of most recent volcanic origin. These radar data were obtained with a surface resolution of 50 to 100 km 2 on January 24 and April 17, 1967. A detailed account of the delay-doppler radar mapping technique can be found in unpublished reports by Thompson.

Nature↗