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On the surface of the Moon a large number of linear features are recognizable. Long and narrow depressions are defined as lunar rilles. Their morphology has different characteristics, related to their origin. Among these, the sinuous rilles represent lineaments considered remnants of shallow lava channels. In this article, a quadrant of the Moon has been analyzed to recognize and map this type of morphology. An accurate morphometric analysis has been accomplished, using the lunar reconnaissance orbiter camera which has a resolution of 100 m/pixel, and the digital elevation model from lunar orbiter laser altimeter with a resolution of 6 m/pixel. A total of 51 sinuous rilles have been recognized in the study area, 18 of which are new, improving a previous catalogue. The resulting quantitative and qualitative measurements were analyze and compared each other' to identify potential morphological trends. Different relationships between morphological parameters have been proposed, and the results enhance the importance of substrate composition in the evolution of these features, emerged mainly from the variations in width and depth values. The linear relationship between these two parameters is consistent with the idea that erosion efficiency acts proportionally in both vertical and horizontal directions. Partial filling phenomena by subsequent lava flows probably occurred in some sinuous rilles located in maria. The hypothesis of a constructive genesis requires further investigation to identify the levees created by sinuous rilles' formation process.

Der auch als ein Nestor der deutschsprachigen Dermatovenerologie apostrophierte Johann Heinrich Rille wurde 1902 als auserordentlicher Professor fur Syphilis und Hautkrankheiten an die zweitalteste deutsche Universitat berufen, nach Leipzig, wo ihm eine spatere ordentliche Professur in Aussicht gestellt wurde. Die Realisierung dieser Zusage verzogerte sich durch den in Deutschland muhsamen Weg der Anerkennung seiner Disziplin als eigenstandiges Fachgebiet und durch weltkriegsbedingte Verschiebungen von Prioritaten. Erst 1919 wurde die uberfallige Ordinariatsverleihung an Rille vollzogen, die er als „erfolgreiche Teilzurucklegung des Leidensweges der deutschen Dermatologie in Leipzig“ kommentierte.

Fine-resolution morphological mapping aided by ortho-images and digital elevation model from Chandrayaan-1 Terrain Mapping Camera and 3D GIS visualization has revealed scientifically diverse characteristics of lunar surface features, due to unique topographical significance of morphological features, i.e., highlands, basaltic plains and craters, which are very well manifested in 3D GIS environment. The distribution of various morphological features provides insights into the sequential evolution and surface process of the study area. The highland region represented by the Fra Mauro formation in the study area exhibits high albedo with distinct topography. The northern part of the study area falls in the southern part of major basin Serenitatis, and exhibits the dark mantling material with low albedo. The morphological features, i.e., wrinkle ridges and rilles, indicate volcanic flow events consequence to the loading of basaltic materials in the interior of the Serenitatis and Imbrium Basins and related extensional failure. The Manilius crater, which occupies the central part of the study area, is a complex crater with a central peak and asymmetric ejecta deposit. The ages of the major surficial features were determined based on size, frequency and distribution pattern of craters using crater size-frequency distribution model. Age of the Fra Mauro highland, Manilius crater, Mare Serenitatis and Mare Vaporum is, respectively, 3.9, 3.5, 2.8 and 1.7 Ga years, indicating that the lunar surface of this region evolved in Imbrian to Eratosthenian age of lunar selenological timescale.

Volcanic channels are common features on the terrestrial planets. They have diverse morphologies including sinuous rilles, channelized flows, and potentially collapsed lava tubes. Many of these channels are a part of a typical igneous assemblage of landforms. In addition, some channels have an ambiguous origin, where a volcanic interpretation explains many of the observed features in some settings. This chapter describes volcanically formed sinuous channels, pitted channels, channelized flows, streamlined forms, platy terrain, and discusses a potential volcanic context for outflow channels and some valley networks on Mars.

Lunar sinuous rilles are large (kilometers long; tens of meters wide) channels commonly found on the lunar maria. Although there is broad consensus that sinuous rilles were generated during lava-flow emplacement, disagreement remains regarding the relative contributions of erosional and constructional processes during rille formation. Careful mapping of portions of Rima Marius (centered at 16.37°N, 49.54°W) using Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) images with resolutions as high as 0.5 m/pixel reveal morphologic evidence for the origin of sinuous rilles. Specifically, shallow (

The objective of this study is to explore the regional geology of the northwest Imbrium region in which the Chang'E-3 (CE-3) landing site is located. CE-3 successfully landed on December 14, 2013 on the unsampled Eratosthenian basalts whose study is important for understanding the evolution of the Moon. New geologic and structural maps of the research area were produced through the integrated analysis of diverse datasets. The highlands surrounding Imbrium differ from typical Farside Highlands Terrain (FHT). The Iridum highland region (as well as the surrounding Imbrium region) exhibits elevated concentrations of Fe, and abundant local exposures of low-Ca pyroxene and olivine bearing lithologies. In this study these highlands are named as mafic highlands (MH). Our dating results using crater size-frequency distributions (CSFDs) show that the Iridum basin (hosting Sinus Iridum) was formed ∼3.8 Ga, shortly following the Imbrium basin formation and before the last large multiringed basin, Orientale. The Eratosthenian period of lunar basalt eruptions, which lasted longer than other stratigraphic units, is suggested to divide into the Lower Eratosthenian mare (LEm) and Upper Eratosthenian mare (UEm) units. This subdivision is based on whether lava fronts can be clearly seen or not and the age separating the units is 2.35 Ga. The mafic mineralogy of the mare basalts in Imbrium is characterized by abundant olivine in the Eratosthenian-aged basalts and average pyroxene compositions near pigeonite to sub-calcic augite in the Imbrian and Em1 units. The thickness of individual lava for UEm units is 8–11 m, indicative of high effusion rates. The thickness of the Em3 unit ranges from ∼17 m to ∼45 m with lesser thickness to the west and greater thickness in the interior and to the east. The estimated volume and average flux of the Eratosthenian-aged basalts are greater than previously thought. The presence of these youngest basalts in the Procellarum-KREEP terrain (PKT) is hypothesized to be a causal relationship, with the PKT terrain reducing the thickness of the lithosphere and permitting preferential dike emplacement and extrusion there. We speculate that high-Ti and olivine-rich composition in late stage basalts may be consistent with low Si and high Ti and low degrees of partial melting. Large numbers of sinuous rilles and small ridges are identified and mapped. Many young ridges were found inside Imbrium, suggesting a very extended period (at least as young as the last 50 Ma) of the Moon's tectonic activity. The distinct compositions of both highlands and mare basalts and extended tectonism emphasize how the Imbrium basin is an important area for understanding the Moon.

Published in the Bloomsbury Social Theory and Methodology in Education Research Series, this book edited by Mike Murphy, Ciaran Burke, Cristina Costa and Rille Raaper critically examines the curren...

Because of the impending energy crisis and the environmental Impact of fossil fuels, researchers are actively looking for alternatives, such as Helium-3 on the Moon. Although it remains challenging to explore energies on the Moon due to the long physical distance, the lunar features, such as craters and rilles, can be the hotspots for such energy sources, according to recent studies. Thus, identifying lunar features, such as craters and rilles, can facilitate the discovery of Helium-3 on the Moon, which is enriched in such hotspots. However, previously, no computational method was developed to recognize the lunar features automatically for facilitating space energy discovery. In our research, we aim at developing the first deep learning method to identify multiple lunar features simultaneously for potential energy source discovery. Based on the state-of-the-art deep learning model, High Resolution Net, our model can efficiently extract semantic information and high-resolution spatial information from the input images, which ensures the performance for recognizing the lunar features. With a novel framework, our method can recognize multiple lunar features, such as craters and rilles, at the same time. We also used transfer learning to handle the data deficiency issue. With comprehensive experiments on three datasets, we show the effectiveness of the proposed method. All the datasets and codes are available online. The source code and the data are available at https://github.com/frankchen121212/High-Resolution-MoonNet

We model the ascent and eruption of lunar mare basalt magmas with new data on crustal thickness and density (GRAIL), magma properties, and surface topography, morphology and structure (Lunar Reconnaissance Orbiter). GRAIL recently measured the broad spatial variation of the bulk density structure of the crust of the Moon. Comparing this with the densities of lunar basaltic and picritic magmas shows that essentially all lunar magmas were negatively buoyant everywhere within the lunar crust. Thus positive excess pressures must have been present in melts at or below the crust–mantle interface to enable them to erupt. The source of such excess pressures is clear: melt in any region experiencing partial melting or containing accumulated melt, behaves as though an excess pressure is present at the top of the melt column if the melt is positively buoyant relative to the host rocks and forms a continuously interconnected network. The latter means that, in partial melt regions, probably at least a few percent melting must have taken place. Petrologic evidence suggests that both mare basalts and picritic glasses may have been derived from polybaric melting of source rocks in regions extending vertically for at least a few tens of km. This is not surprising: the vertical extent of a region containing inter-connected partial melt produced by pressure-release melting is approximately inversely proportional to the acceleration due to gravity. Translating the ∼25 km vertical extent of melting in a rising mantle diapir on Earth to the Moon then implies that melting could have taken place over a vertical extent of up to 150 km. If convection were absent, melting could have occurred throughout any region in which heat from radioisotope decay was accumulating; in the extreme this could have been most of the mantle. The maximum excess pressure that can be reached in a magma body depends on its environment. If melt percolates upward from a partial melt zone and accumulates as a magma reservoir, either at the density trap at the base of the crust or at the rheological trap at the base of the elastic lithosphere, the excess pressure at the top of the magma body will exert an elastic stress on the overlying rocks. This will eventually cause them to fail in tension when the excess pressure has risen to close to twice the tensile strength of the host rocks, perhaps up to ∼10 MPa, allowing a dike to propagate upward from this point. If partial melting occurs in a large region deep in the mantle, however, connections between melt pockets and veins may not occur until a finite amount, probably a few percent, of melting has occurred. When interconnection does occur, the excess pressure at the top of the partial melt zone will rise abruptly to a high value, again initiating a brittle fracture, i.e. a dike. That sudden excess pressure is proportional to the vertical extent of the melt zone, the difference in density between the host rocks and the melt, and the acceleration due to gravity, and could readily be ∼100 MPa, vastly greater than the value needed to initiate a dike. We therefore explored excess pressures in the range ∼10 to ∼100 MPa. If eruptions take place through dikes extending upward from the base of the crust, the mantle magma pressure at the point where the dike is initiated must exceed the pressure due to the weight of the magmatic liquid column. This means that on the nearside the excess pressure must be at least ∼19 ± 9 MPa and on the farside must be ∼29 ± 15 MPa. If the top of the magma body feeding an erupting dike is a little way below the base of the crust, slightly smaller excess pressures are needed because the magma is positively buoyant in the part of the dike within the upper mantle. Even the smallest of these excess pressures is greater than the ∼10 MPa likely maximum value in a magma reservoir at the base of the crust or elastic lithosphere, but the values are easily met by the excess pressures in extensive partial melt zones deeper within the mantle. Thus magma accumulations at the base of the crust would have been able to intrude dikes part-way through the crust, but not able to feed eruptions to the surface; in order to be erupted, magma must have been extracted from deeper mantle sources, consistent with petrologic evidence. Buoyant dikes growing upward from deep mantle sources of partial melt can disconnect from their source regions and travel through the mantle as isolated bodies of melt that encounter and penetrate the crust–mantle density boundary. They adjust their lengths and internal pressure excesses so that the stress intensity at the lower tip is zero. The potential total vertical extent of the resulting melt body depends on the vertical extent of the source region from which it grew. For small source extents, the upper tip of the resulting dike crossing the crust–mantle boundary cannot reach the surface anywhere on the Moon and therefore can only form a dike intrusion; for larger source extents, the dike can reach the surface and erupt on the nearside but still cannot reach the surface on the farside; for even larger source extents, eruptions could occur on both the nearside and the farside. The paucity of farside eruptions therefore implies a restricted range of vertical extents of partial melt source region sizes, between ∼16 and ∼36 km. When eruptions can occur, the available pressure in excess of what is needed to support a static magma column to the surface gives the pressure gradient driving magma flow. The resulting typical turbulent magma rise speeds are ∼10 to a few tens of m s−1, dike widths are of order 100 m, and eruption rates from 1 to 10 km long fissure vents are of order 105 to 106 m3 s−1. Volume fluxes in lunar eruptions derived from lava flow thicknesses and surface slopes or rille lengths and depths are found to be of order 105 to 106 m3 s−1 for volume-limited lava flows and >104 to 105 m3 s−1 for sinuous rilles, with dikes widths of ∼50 m. The lower end of the volume flux range for sinuous rilles corresponds to magma rise speeds approaching the limit set by the fact that excessive cooling would occur during flow up a 30 km long dike kept open by a very low excess pressure. These eruptions were thus probably fed by partial melt zones deep in the mantle. Longer eruption durations, rather than any subtle topographic slope effects, appear to be the key to the ability of these flows to erode sinuous rille channels. We conclude that: (1) essentially all lunar magmas were negatively buoyant everywhere within the crust; (2) positive excess pressures of at least 20–30 MPa must have been present in mantle melts at or below the crust–mantle interface to drive magmas to the surface; (3) such pressures are easily produced in zones of partial melting by pressure-release during mantle convection or simple heat accumulation from radioisotopes; (4) magma volume fluxes available from dikes forming at the tops of partial melt zones are consistent with the 105 to 106 m3 s−1 volume fluxes implied by earlier analyses of surface flows; (5) eruptions producing thermally-eroded sinuous rille channels involved somewhat smaller volume fluxes of magma where the supply rate may be limited by the rate of extraction of melt percolating through partial melt zones.

International audience; Mare Tranquillitatis corresponds to the deposit of successive Early to Late Imbrian basaltic units filling the Tranquillitatis basin on the Moon. The present study focuses on the western half of the mare, in the vicinity of the Arago crater (6.16°N, 21.42°E). High resolution datasets from recent remote sensing missions were used to reconstruct the geologic history of the area, which includes a variety of geological features such as: 8 extrusive domes, numerous wrinkle ridges, a sinuous rille and 37 Irregular Mare Patches (IMPs). We performed crater counting to date the domes emplacement and estimated the domes lava rheologic properties (plastic viscosities, lava effusion rates, and durations of effusion) using their geometric characteristics. As a result we classify the Arago domes into three groups: E1-type domes (Arago 1 and 8), H1-type domes (Arago 4 to 7), and B-type domes (Arago 2 and 3) respectively emplaced ​~ ​3.7 ​Ga, ~3.4 ​Ga, and ~2.8 ​Ga ago. IMPs are observed in the younger mare unit and on the top of the Arago 6 dome; they likely correspond to a late stage of waning mare volcanism in the area. Both IMPs and domes have a composition similar to the surrounding mare in the VNIR spectral domain, consistent with mafic materials. The exceptionally long-lived volcanism and its diversity recorded in the Arago region may be related to both a Th-rich anomaly reported nearby and to the large-scale magma center responsible for the Lamont positive Bouguer anomaly. In addition, volcanic features of the Arago region are superimposed on a Ti-rich mare unit visited by the Apollo 11 crew 175 ​km to the south at Tranquility Base. The geological and historical richness of this region makes it a compelling site for future science and/or In Situ Resources Utilization (ISRU) driven missions to the Moon.

Some areas of the Moon’s surface are crisscrossed by kilometers-long linear depression features; “cracks” as Wilkins and others called them. Many of these features do appear to be simply cracks, but their true nature is more complex than that. The classification of these linear features depends primarily on their particular creative processes. The shallow fault trace or meandering river-like features are all called rilles. The generally deeper and wider linear depressions are known as either a catena (crater chain) or a vallis (valley). In this chapter we will observe these linear features and cover the different endogenic and external processes by which they were formed.

Lunar rilles are any of the long, narrow depressions on the surface of the Moon. These structures have different characteristics, which are related to their origin. Here, a classification of the lunar rilles in different groups with similar morphometric features and likely the same formation mechanisms is proposed. The detection, classification and mapping of lunar rilles has been achieved in two quadrants of the northern hemisphere, which are located between -90°E to 90°E longitude and 0°N to 60°N latitude. For the detection and mapping of rilles, we used images from the Lunar Reconnaissance Orbiter Camera (LROC) [1] which have a resolution of 100 m/pixel and the DEM from Lunar Orbiter Laser Altimeter (LOLA) with a resolution of 6 m/pixel. This work is part of an international cooperation between Italy and China called "Moon Mapping project" for the collaboration between Italian and Chinese college students.

Charon displays extensive plains that cover the equatorial area and south to the terminator on the sub-Pluto hemisphere observed by New Horizons. We hypothesize that these plains are a result of Charon's global extension and early subsurface ocean yielding a large cryoflow that completely resurfaced this area leaving the plains and other features that we observe today. The cryoflow consisted of ammonia-rich material, and could have resurfaced this area either by cryovolcanic effusion similar to lunar maria emplacement or a mechanism similar to magmatic stoping where lithospheric blocks foundered. Geological observations, modeling of possible flow rheology, and an analysis of rille orientations support these hypotheses.

Chang'e-5, China's first lunar sample return mission, is targeted to land in northern Oceanus Procellarum, within a region selected on the basis of 1) its location away from the Apollo-Luna sampling region, 2) the presence of the Procellarum KREEP Terrane (PKT), 3) the occurrence of one of the youngest lunar mare basalts (Em4), and 4) its association with Rima Sharp. In order to provide context for returned sample analyses, we conducted a comprehensive study of the regional and global settings, geomorphology, composition, mineralogy, and chronology of the Em4 mare basalts. Superposed on Imbrian-aged low-Ti basalts, Em4 covers 37,000 km2 and is composed of Eratosthenian-aged (∼1.53 Ga), high-Ti basalts with a mean thickness of ∼51 m and a volume between ∼1450 and 2350 km3. Minor variations in TiO2 and FeO abundance occur within the unit and the thorium content averages ∼6.7 ppm, typical of PKT mare basaltic regolith. No specific source vents (e.g., fissures, cones, domes) were found within the unit. We show that Rima Sharp is actually composed of three major rilles, whose source vents are located outside of, and which flow into, and merge in Em4, suggesting that they may be among the sources for Em4. Regolith thickness averages ∼7 m and there is abundant evidence for vertical and lateral mixing; the most likely sources of distal ejecta are Aristarchus, Harpalus, and Sharp B craters. Returned samples from local and distant materials delivered by impact will thus provide significant new insights into lunar geochronology, inner Solar System impact fluxes, the age of very young mare basalts, the role of the PKT in the generation of mare basalts, the role of sinuous rilles in lava flow emplacement, and the thermal evolution of the Moon.

NASA's GRAIL mission employed twin spacecraft in polar orbits around the Moon to measure the lunar gravity field at unprecedentedly high accuracy and resolution. The low spacecraft altitude in the extended mission enables the detection of small-scale surface or subsurface features. We analyzed these data for evidence of empty lava tubes beneath the lunar maria. We developed two methods, gradiometry and cross-correlation, to isolate the target signal of long, narrow, sinuous mass deficits from a host of other features present in the GRAIL data. Here, we report the discovery of several strong candidates that are either extensions of known lunar rilles, collocated with the recently discovered “skylight” caverns, or underlying otherwise unremarkable surfaces. Owing to the spacecraft polar orbits, our techniques are most sensitive to east-west trending near-surface structures and empty lava tubes with minimum widths of several kilometers, heights of hundreds of meters, and lengths of tens of kilometers.

The Fe-Ni-Cu sulfide ores at Kambalda, Western Australia, are interpreted to be the result of thermomechanical erosion of underlying rocks by the host komatiite lava flows. However, there is a long-standing argument about the extent of the erosion process, and the degree to which the linear embayments that host the ores were eroded by lava as opposed to formed by tectonic processes. This controversy has fundamental implications for the origin of magmatic sulfide ore, as well as for sinuous rilles on terrestrial planets. The controversy at Kambalda hinges on pinchout features, where sulfide ore at the edges of embayments penetrates laterally into footwall rocks. The most recently published studies of these features interpret them as forming by thrusting of basalts over sulfide-komatiite contacts along the margins of tectonic embayments. Field evidence and X-ray fluorescence element mapping on underground exposures in the Moran deposit demonstrate that sulfide liquid melted its way both downward and laterally into basalt, generating complex plumose melt layers, melt emulsions, and hybridized chromite-decorated contacts. These observations confirm an origin for the pinchouts by thermomechanical erosion, driven by the high temperature, high density, and low viscosity of the sulfide melt. They also provide some intriguing insights into the nature of interactions between sulfide melt and melting silicate rocks in magmatic Ni-Cu-platinum group element sulfide ore deposits in general.

The lunar maria cover approximately 17% of the Moon's surface. Discerning discrete subsurface layers in the mare provides some constraints on thickness and volume estimates of mare volcanism. Multiple types of data and measurement techniques allow probing the subsurface and provide insights into these layers, including detailed examination of impact craters, mare pits and sinuous rilles, and radar sounders. Unfortunately, radar sounding includes many uncertainties about the material properties of the lunar surface that may influence estimates of layer depth and thickness. Because they distribute material from depth onto the surface, detailed examination of impact ejecta blankets provides a reliable way to examine deeper material using orbital instruments such as cameras, spectrometers, or imaging radars. Here, we utilize Miniature Radio Frequency (Mini-RF) data to investigate the scattering characteristics of ejecta blankets of young lunar craters. We use Circular Polarization Ratio (CPR) information from twenty-two young, fresh lunar craters to examine how the scattering behavior changes as a function of radius from the crater rim. Observations across a range of crater size and relative ages exhibit significant diversity within mare regions. Five of the examined craters exhibit profiles with no shelf of constant CPR near the crater rim. Comparing these CPR profiles with LROC imagery shows that the magnitude of the CPR may be an indication of crater degradation state; this may manifest differently at radar compared to optical wavelengths. Comparisons of radar and optical data also suggest relationships between subsurface stratigraphy and structure in the mare and the block size of the material found within the ejecta blanket. Of the examined craters, twelve have shelves of approximately constant CPR as well as discrete layers outcropping in the subsurface, and nine fall along a trend line when comparing shelf-width with thickness of subsurface layers. These observations suggest that surface CPR measurements may be used to identify near-surface layering. Here, we use ejected material to probe the subsurface, allowing observations of near-surface stratigraphy that may be otherwise hidden by layers higher from remote observations.

In general, textures are thought to be some complicated repeated patterns formed by elements, or primitives which are sorted in certain rules. Lunar surfaces record the interactions between its outside environment and itself, thus, based on high-resolution DEM model or image data, there are some topographic features which have different roughness and entropy values or signatures on lunar surfaces. Textures of lunar surfaces can help us to concentrate on typical topographic and photometric variations and reveal the relationships between obvious features (craters, impact basins, sinuous rilles (SRs) and ridges) with resurfacing processes on the Moon. In this paper, the term surface roughness is an expression of the variability of a topographic or photometric surface at kilometer scale, and the term entropy can characterize the variability inherent in a geological and topographic unit and evaluate the uncertainty of predictions made by a given geological process. We use the statistical moments of gray-level histograms in different-sized neighborhoods (e.g., 3, 5, 10, 20, 40 and 80 pixels) to compute the kilometer-scale roughness and entropy values, using the mosaic image from 70°N to 70°S obtained by Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera (WAC). Large roughness and entropy signatures were only found in the larger scale maps, while the smallest 3-pixel scale map had more disorderly and unsystematic textures. According to the entropy values in 10-pixel scale entropy map, we made a frequency curve and categorized lunar surfaces into three types, shadow effects, maria and highlands. A 2D scatter plot of entropy versus roughness values was produced and we found that there were two point clusters corresponding to the highlands and maria, respectively. In the last, we compared the topographic and photometric signatures derived from Lunar Orbiter Laser Altimeter (LOLA) data and WAC mosaic image. On the lunar surfaces, the ridges have obvious multilevel topographic textures which are sensitive to the topographic changes, while the ejecta deposits of fresh craters appear obvious photometric textures which are sensitive to the brightness variations.

In this paper, we estimated the relative and absolute ages of the seven rilles (1–7) in southwest Aristarchus region in order to know when these lunar rilles formed and how they fit into lunar volcanic history. According to their superposition relationships and colors in the color-ratio composite, the geological units and features in the study area were sorted in an order from old to young: the highland materials, the glassy Fe 2+ rich pyroclastics (DMD), the rille 1, 2, 3, 5, and 7, the mature and fresh basaltic units in the east and south of the Aristarchus plateau, the rille 4 and 6, the youngest Aristarchus Craters and its ejecta deposits. Buffered Crater Counting (BCC) method provides a chance to determine ages of linear features that do not have enough surface areas for the traditional crater counting method. The BCC analysis of seven rilles had shown that five of them probably formed in the Imbrium Period and the other two formed in Eratosthenian Period. The absolute age of oldest rille is 3.77 − 0.04 + 0.03 Ga and the youngest rille׳s age is 1.49 − 0.26 + 0.26 Ga . Because their formation is interpreted to lava flowing and eroding of magma eruptions, we can see that the volcanic activities in Aristarchus region lasted for a long time from Pre-Nectarian Period (DMD materials) to Eratosthenian Period (rille 6) and weakened gradually to form small scale rilles as times went on. This may be because of the basaltic volcanic eruptions produced by heating elements in Aristarchus region to partially melt the underlying lunar mantle, which become the materials and source of these rilles.

Basaltic eruptive fissures of the Great Rift and surroundings on the eastern Snake River Plain of Idaho, USA, and selected volcanic features in Hawai’i, Iceland and northern Africa were surveyed for their relevancy as planetary analogs. Evaluated during field investigations and in satellite imagery for structures, physiography, and geologic setting, fissures were categorized into four broad types: (1) simple, monogenetic fissures with obvious volcanic constructs or deposits, (2) monogenetic fissures now obscured by low shields or relatively large cones, (3) polygenetic volcanic rift zones with multiple vents and deposits, and (4) compound regional fissure systems or dike swarms that comprise major rift zones or large volcanic terrains. Using this classification as an initial base, we surveyed imagery of volcanic features for likely fissure vents in two major geologic settings on the Moon: floor-fractured craters (FFCs) and mare and cryptomare provinces. Two major regions on Mars, the volcanic plains around Alba Mons and the greater Tharsis region, were also surveyed for fissure types and volcanic associations of fissure-like features. The planetary surveys suggest that the proposed classification provides a suitable analog starting point to interpret structures associated with fissure systems on the Moon and Mars. With few exceptions, our survey indicates that each of the studied terrains exhibits a dominant fissure type. Type 1 fissures, most with pyroclastic deposits, prevail in lunar FFCs and mare-like regions; whereas type 2 fissures are ubiquitous in the Tharsis region of Mars and a few exist on the Moon as low shields. Type 3 volcanic rift zones are not common on either the Moon or Mars, although they might become evident in future work on chemically evolved terrains. Type 4 fissures are inferred in mare terrains, often represented as the extensions of major linear rille networks or rimae, with possibly complex dike swarms that were buried beneath voluminous mare basalt lava flows. Likewise, numerous flood lavas on Mars are possibly associated with now-obscured or difficult to define type 4 fissure systems.

Large shield-building volcanic structures (>30 km) with central vents are rare on the Moon. The most popular candidate targets of lunar large shield volcanoes are volcanic complexes on the lunar nearside within the compositionally evolved Procellarum KREEP terrane (PKT). However, there is a unique mass concentrated volcanic complex not within the PKT, namely Gardner (16.1°N, 34.1°E, ∼70 km in diameter) on the northern edge of Mare Tranquillitatis, whose origin is enigmatic. Here we use multi-source remote-sensing data to assess its morphology, composition and stratigraphy to better understand its formation and evolution. Results show that domes, sinuous rilles, and an irregular depression exist in this region. Gardner has experienced four stages of volcanic activities with absolute model ages from 3.90 to 2.96 Ga, contemporaneous with the main volcanic activity periods of the lunar nearside. An area with relatively low albedo, high FeO and TiO2 contents, low rock abundances, and young surface age is identified in the southeast part of the irregular depression at the summit of the plateau, which could have been the result of a long-lived eruptive center. Quasi-circular positive Bouguer-gravity anomaly suggests either sill/laccolith intrusions or large conduit solidifications underneath this area, which could be related to its surrounding radially distributed lava domes, wrinkle ridges and faults. We conclude that Gardner is the largest central-vent volcano identified so far on the Moon, and it provides an essentially new perspective and supplement for the knowledge of the lunar nearside volcanism.

We have investigated the links between regional stress fields, the volcanic centers, rifts, graben and channels in the NW region of the Elysium Province (Fig 1(a) and Fig 1(b)) to determine whether the sequence of stress events occurring during province development can be derived from the morphologies of these features; and thus provide a sequence of development events, which is independent of surface dating techniques. Rift and graben geomorphology was mapped and the neighboring relationships and orientation of individual graben were assessed to determine any spatial clustering or preferred orientation with regional or surface features capable of creating lithospheric flexure or tectonic stress within the study area. Crosscutting analysis determined a time ordered sequence of graben formation and these were related to volcanic centers or regional sources of stress. In addition, mapping showed that different channels share sections with similar shape and orientation, prompting our study of whether these channels, in tandem with the graben, were tectonically influenced during their development. The channel central axes were mapped and compared to identify common sequences of channel direction change. The time sequence of channel direction changes and the time ordered sequence of graben development were then compared. We have demonstrated a correlation between rift and graben direction with channel orientation suggesting a regional stress control from evolving volcanic centers. Overall we derive, for the first time, the temporal pattern of tectonic, volcanic and channel evolution for the northwestern region of this major magmatic province on Mars.

Marius Hills volcanic complex is one of the most important regions on the lunar surface having an abundant number of volcanic features like domes and cones. Systematic mapping of 106 domes/cones in the Marius Hills region was carried out in this study using high-resolution orthoimage and digital elevation models of Chandrayaan-1 and Kaguya missions. Various morphometric parameters like diameter, height, volume, flank slope, circularity index and form factor are derived for all the mapped domes. The rheological parameters, such as viscosity and eruption rate are estimated for isolated domes and cones superimposed over low domes. The morphometric and rheological properties of these domes are comparable to those located in the area near to Hortensius crater and other mare regions. Surface ages derived for a selected region in NW portion of the Marius Hills volcanic complex using crater size-frequency distribution technique yields ages of 2.98 and 1.91 Ga. It suggests that the domes in this region formed at about 2.98 Ga ago, and then, the younger mare basalts likely embayed this region about 1.98 Ga ago. Stratigraphic sequence of rilles, wrinkle ridge and domes shows that wrinkle ridges are the oldest, while the rilles are younger than the domes.

Domes, an analog of the terrestrial shield volcanoes are one of the important volcanic features found on the lunar surface. Such volcanic features are windows to better understanding of the contrasting natures of lunar volcanism, giving an insight into the source and the nature of the basaltic magmas. Marius Hills Complex is one of the most important regions in the entire lunar surface for having a complex setting of volcanic constructs with an abundant number of volcanic features like domes, cones and rilles. As a part of initiation of the study of Marius Hills volcanism, an effusive dome located to the south of Rima Galilaei, near the contact of Imbrian and Eratosthenian geological units is taken for the present study. Inferring from the Terrain Mapping Camera-Digital Elevation Model (TMC-DEM), the morphometric parameters are estimated (350 m in height, 9.62 km in diameter), and accordingly the rheological parameters are also estimated. As the signatures of multiphase eruption are not clear geomorphologically and also in topography, the dome is assumed to evolved in monogenetic eruption. The causative dike parameters of the dome are estimated, which gives upper bounds of true values of the parameters. The estimated feeder dike length (150 km) and width (233 m) implies that the source region is lying most probably in the mantle portion of moon. The crater size frequency distribution (CSFD) is applied to determine the age of the particular dome and also the surrounding mare surface so as to better construct a stratigraphic correlation. It is found that dome belongs to oldest age unit of Marius Hills region while the surrounding units are relatively younger. Using Chandrayaan-I Moon Mineralogy Mapper (M3) data, the surface composition for the study area is also analysed. Thus, the morphometry, rheology, dike parameters, age determination and mineralogy are found to be in good agreement with results of the earlier studies. Such a study, covering all the domes and other volcanic features in Marius Hills using high resolution data sets will provide a clear and better understanding of the volcanic history of the region and the Oceanus Procellarum Basin as well. In such a study, the application potential of high resolution Chandrayaan-I TMC image and its DEM generated from the stereo data has been useful.

Accepted: 2014-06-11, 資料番号: SA1140139000

The Lunar Radar Sounder (LRS) onboard Kaguya (SELENE) detected widespread horizontal reflectors under some nearside maria. Previous studies estimated that the depths of the subsurface reflectors were up to several hundreds of meters and suggested that the reflectors were interfaces between mare basalt units. The comparison between the reflectors detected in the LRS data and surface age maps indicating the formation age of each basalt unit allows us to discuss the lower limit volume of each basalt unit and its space and time variation. We estimated volumes of basalt units in the ages of 2.7 Ga to 3.8 Ga in the nearside maria including Mare Crisium, Mare Humorum, Mare Imbrium, Mare Nectaris, Mare Serenitatis, Mare Smythii, and Oceanus Procellarum. The lower limit volumes of the geologic units estimated in this study were on the order of 103 to 104 km3. This volume range is consistent with the total amount of erupted lava flows derived from numerical simulations of thermal erosion models of lunar sinuous rille formation and is also comparable to the average flow volumes of continental flood basalt units formed after the Paleozoic and calculated flow volumes of Archean komatiite flows on the Earth. The lower limits of average eruption rates estimated from the unit volumes were on the order of 10−5 to 10−3 km3/yr. The estimated volumes of the geologic mare units and average eruption rate showed clear positive correlations with their ages within the same mare basin, while they vary among different maria compared within the same age range.

The Sinus Iridum region is one of the most important candidate landing targets for Chinese lunar landing mission ChangE-3 (CE-3). Because of its flat topography, complex evolution history and abundance of geological features, it shows great significance to both science and engineering. There are abundant geological features, such as winkle ridges, mare rilles, impact craters and crater chains in this region, indicating complex evolution history. In this paper, we use Lunar Reconnaissance Orbiter (LRO) Altimeter (LOLA) and Camera (LROC) data to characterize regional topography and geological features. We deduce the iron and titanium content from Clementine ultraviolet-visible (UVVIS) data and generate mineral absorption features from the Chandrayaan-1 Moon Mineralogy Mapper (M3) imaging spectrum data. Results show that this region has experienced four magmatic events. The composition of these basaltic materials filled in different time changes from low-titanium basalts in earlier time to medium-titanium basalts in later time. The inner Sinus Iridum has a composition of mature and pyroxene-rich materials, but olivine abundance of these pyroxene-rich materials increases from old to young. The surrounding highlands have a dominantly feldspathic composition. In the north wall, there exposed some possible mantle origin olivine-rich materials. The comparable flat topography condition and abundant geological features make Sinus Iridum an excellent site to carry out in-site analyses and rover exploration.

Marius Hills is a large volcanic complex on the Oceans Procellarum of the lunar nearside. Numerous volcanic features, including domes, cones, and rilles occur in this region. Due to limitations in lunar remote sensing data, most previous studies on this region focused on its morphological and geochemical properties but little was known about the subsurface and interior structures of this volcanic complex. Knowledge of the local crustal density is meaningful to both determine the composition for this volcanic complex and understand the crustal evolutionary history for this region. Constraining the lithospheric thickness in this region is helpful to estimate the heat flux at the time of volcanic loading, which is a crucial parameter to study the thermal evolutionary history of the nearside mantle. Here, we applied a localized gravity and topography admittance analysis for the Marius Hills region to constraint its crustal density and lithospheric thickness. The gravity filed is modeled using a thin elastic lithspheric model that considers both surface and subsurface loads. Localized admittance and correlations spectra are used to constrain these modeled parameters. The best-fit crustal density in our model is ~3040 kg m-3, which is much higher than the average lunar crustal density as 2550 kg m-3, indicating that magma chambers or sills has intruded to the shallow crust and/or that intrusive magma has filled up the porous subsurface crust. The total volume of basalts emplaced in the Marius Hills region is ~2.9×104 km3, suggesting that Marius Hills is a major volcanic center in the Oceanus Procellarum. The best-fit lithospheric thickness of this region is constrained to be as small as ~4 km, indicating that a significant amount of heat production elements have concentrated in this region during the formation of the volcanic complex. This result is consistent with the previous spectral studies that heat production elements (such as thorium) are more abundant in the Oceanus Procellarum.

Lunar sinuous rilles (SRs) are enigmatic features interpreted to have formed as the result of lava erosion into the lunar surface. While specific SRs have been studied in detail over the past few decades, the most recent general survey of these features was conducted in 1969 using Lunar Orbiter IV and V photographs. The current global study updates the catalog of SRs, using higher resolution SELENE and LRO image and topography data to provide detailed observations and measurements of the rilles observed across the lunar surface. The new survey catalogs more than 200 SRs that vary in length from 2 km to 566 km (median length 33.2 km), in width from 160 m to 4.3 km (median width 480 m), in depth from 4.8 m to 534 m (median depth 49 m), in slope from −1.4° to 0.5° (median slope −0.2°), and in sinuosity index from 1.02 to 2.1 (median sinuosity 1.19). Oceanus Procellarum contains 48% of the rilles mapped in this survey, and these rilles are typically associated with the known centers of volcanism within the Procellarum-KREEP Terrain, the Aristarchus Plateau and the Marius Hills. The current study also constrains the timing of the formation of lunar SRs, using the assumptions that the incised unit represents an upper age limit and the terminal or embaying unit represents a lower age limit. Results indicate that the distribution of ages of rille formation is highly correlated with the emplacement ages of mare units, where the majority of rilles are observed to have formed between 3.0 Ga and 3.8 Ga ago, though some of the features associated with the Aristarchus Plateau may have formed as recently as 1.0 Ga to 1.5 Ga ago. The documented observations can be used to better understand how SRs formed; for example, the range of slopes observed for all rilles (−1.4° to 0.5°) indicates that thermal erosion is likely dominant during the formation of the 78% of rilles that are observed to have formed in solidified mare basalt material, though mechanical erosion is likely to have been a more significant process during the formation of the 25% of observed rilles that originate in the highlands (20% of the mapped rilles crossed from the highlands into the mare), where a thicker regolith is expected to have been more easily eroded.

Phase equilibrium experiments have been performed to place constraints on the melting processes in the lunar interior using the Apollo 15 group A ultramafic green glass, the most abundant pyroclastic glass composition found in the polymict regolith breccia (15426) near Hadley Rille at station 7. Experiments on two compositional end members of the 15A green glass trend yield experiments saturated with olivine and orthopyroxene on the liquidus at 1520 °C and 2.1 GPa. Experiments were also performed on high-Al and -Ca analog compositions and on mixtures of the green glass compositions and natural minerals (olivine, orthopyroxene and garnet) in order to obtain experimental liquids multiply saturated with olivine, orthopyroxene, clinopyroxene and garnet. Three liquid compositions in equilibrium with a garnet-lherzolite residual phase assemblage were produced at 2.35 GPa, 1440 and 1420 °C and at 2.6 GPa, 1460 °C. Observed compositional variations in the 15A glasses rule out any simple partial melting process that would involve a olivine + orthopyroxene bearing source region. The results of these experiments are used to test petrogenetic models for the origin of the 15A green glasses. Synergistic evidence from major and trace element geochemistry, geophysical data on the lunar interior structure and results from models of lunar magma ocean differentiation is used to develop a model for the origin of the 15A ultramafic glasses. We propose that a mixing process involving a primary magma, derived by melting primordial lunar mantle, and remelted late-stage magma ocean cumulates led to the origin of the 15A glass. The model uses the 15A green glass multiple saturation point at 1520 °C and 2.1 GPa to constrain the depth of a cumulate remelting process. Decompression partial melting of undifferentiated lunar mantle, produced by adiabatic upwelling of the deep, hot interior of the moon, produced melts that infiltrated and selectively melted late stage magma ocean cumulates that had sunk to the base of a lunar magma ocean. The compositional variations observed in the 15A glasses are consistent with this model.

A new optical remote-sensing technique called phase-ratio imagery, which suggests an estimation of sub-resolution roughness of the lunar surface, is presented. Lunar images acquired by the Narrow Angle Camera on the Lunar Reconnaissance Orbiter are used. The technique is applied to the 3D phase-ratio imagery of Vallis Schr teri region. This allows observations of patterns of complicated movements of regolith materials on the rille flank, which can be attributed to regolith/debris taluses, definitely not to impact melt as this structure is not associated with an impact crater.

Typical flow thicknesses of lunar mare basalts were not well constrained in the past, because as craters and rilles age, downslope movement of loose material tends to mix and bury stratigraphy, obscuring the three dimensional nature of the maria. New Lunar Reconnaissance Orbiter Camera high resolution images unambiguously reveal thicknesses of mare basalt layers exposed in impact craters, rilles, and steep-walled pits. Pits up to one hundred meters deep present relatively unmodified, near-vertical sections of mare in three cases, and many young impact craters also expose well preserved sections of mare. Oblique views of each pit and many of these craters reveal multiple layers, 3 to 14 m thick, indicating that eruptions typically produced a series of ∼10 m thick flows (or flow lobes) rather than flows many tens to hundreds of meters thick. Additionally, these images unambiguously show that the floors of two pits extend beneath the mare surfaces, thus revealing sublunarean voids of unknown lateral extent. We also document the occurrence of pits that may be expressions of collapse into subsurface voids in non-mare impact melt deposits. These voids are compelling targets for future human and robotic exploration, with potential as temporary shelters, habitations, or geologic museums.

Intact lunar lava tubes offer a pristine environment to conduct scientific examination of the Moon's composition and potentially serve as secure shelters for humans and instruments. We investigated the SELENE Lunar Radar Sounder (LRS) data at locations close to the Marius Hills Hole (MHH), a skylight potentially leading to an intact lava tube, and found a distinctive echo pattern exhibiting a precipitous decrease in echo power, subsequently followed by a large second echo peak that may be evidence for the existence of a lava tube. The search area was further expanded to 13.00–15.00°N, 301.85–304.01°E around the MHH, and similar LRS echo patterns were observed at several locations. Most of the locations are in regions of underground mass deficit suggested by GRAIL gravity data analysis. Some of the observed echo patterns are along rille A, where the MHH was discovered, or on the southwest underground extension of the rille.

Marius Hills is a volcanic plateau on the nearside of the Moon. It is of great interest for its high concentration of volcanic features, including domes, cones, ridges, and rilles. However, the morphological and chronological characteristics of this plateau were not well studied due to the low resolution of early mission data. This study describes the detailed morphology of the volcanic features using the latest high spatial resolution images of the Terrain Camera (TC) onboard Selene-1 (10 m/pix) and Narrow Angle Camera (NAC) onboard the Lunar Reconnaissance Orbiter (LRO) (0.5 m/pix). We report here some new structures such as skylights and remnants of lava tubes. We have divided spectrally homogenous areas with Clementine UVVIS data and did crater size frequency distribution (CSFD) measurements with Lunar Orbiter (LO) IV and TC images in every spectral unit. We first report absolute model ages of 1.10 Ga for Marius basalt 1, 1.49 Ga for Flamsteed basalt, and 1.46 Ga for Schiaparelli Basalt. In addition, we have identified several younger lava events: they are Marius basalt 2 (814 Ma), medium to low titanium basalt (949 Ma), and undifferentiated medium titanium basalt (687 Ma). Finally, we propose a mantle plume scenario for the formation of Marius Hills, which

Virtually all of the economic Ni–Cu–(platinum group element (PGE)) mineralization in the central part of the Cape Smith Belt of New Quebec is hosted by thick olivine cumulate units in the Katinniq Member of the Raglan Formation at the base of the 1.9 Ga Chukotat Group. These units transgress underlying gabbros and pelitic metasediments, forming 50–200-m deep and 300–1,000-m wide V-shaped embayments and have been interpreted on the basis of surface geology, deep diamond core drilling, and magnetic inversion models to represent the remnants of one or more large, long (at least 20 km, possibly ≥50 km), sinuous, komatiitic basalt lava channels that formed by thermomechanical erosion of their substrates. We have used a mathematical model to test these hypotheses regarding komatiitic lava emplacement and erosion by lava. Our modeling predicts that an initially 10-m thick komatiitic basalt flow should have flowed turbulently near the vent and should have thermomechanically eroded unconsolidated pelitic sediment during emplacement to reach the observed degree of contamination of ≤10% at distances of ~30–60 km downstream from the source. Furthermore, our models predict that, at these distances downstream, a fully inflated 100-m thick komatiitic basalt flow would have had thermal erosion rates over consolidated gabbroic substrate of ~0.7–1.5 m/day, requiring ~70–140 days to incise a 100-m deep channel, depending on the initial temperature of the lava, the paleoslope, and the initial temperature and solidus temperature of the gabbro. These erosion rates would have been associated with volumetric flow rates of >105–106 m3/s and eruption volumes of >103–104 km3. Although these flow rates are orders of magnitude larger than those of most modern terrestrial basaltic flows, they are of the same order as those estimated for the largest terrestrial flood basalt flows and with those inferred for some of the largest extraterrestrial flows. Our predicted flow volumes are also of the same order as those of the largest terrestrial flood basalt units, consistent with the great thickness and widespread distribution of the Chukotat Group. Our modeling of thermomechanical erosion of gabbro by komatiitic basalt results in negligible contamination ( Middle REE–Heavy REE > Nb–Ta–Ti represent contamination by underlying Povungnituk semipelites. This result is consistent with present models for the genesis of the Ni–Cu–(PGE) mineralization in the Raglan Formation that involve thermomechanical erosion of unconsolidated, sulfidic semipelitic sediments, and decoupling of the miscible silicate and immiscible sulfide components.

Lunar volcanic complexes are prominent features with a high concentration of various volcanic characteristics. They are ideal objects to study the lunar nearside volcanic activity and its thermal evolution. The Gardner volcanic complex is located in the nearside of the Moon, between Mare Serenitatis and Mare Tranquillitatis. It has a series of volcanic features, such as domes and rilles, which make it an ideal object to study the lunar volcanic history. In this study, we make use of recent high-resolution lunar images (Terrain Camera, TC) and multispectral data (Clementine UVVIS) to study the topography, geomorphologic features, iron and titanium contents, and the geochronology of the Gardner volcanic complex. We identified and analyzed different geomorphologic features, such as impact craters, domes, massifs, scarps, and a suspected fault. Spectral analyses indicated that the Gardner region is covered by low-Ti basalt. Absolute model ages of the different units in the Gardner region were obtained using crater size-frequency distribution (CSFD) measurement. The results show that Gardner may have experienced three periods of volcanic activities, which were aged between Nectarian and Imbrium. The volcanic eruption may decrease with time. The relatively high crustal density and the positive Bouguer gravity anomaly of Gardner show that the Gardner volcanic complex is composed of dense volcanic materials on the surface and in the subsurface. An irregular steep-sided depression is located in the central area of the Gardner plateau, which is different from the depression caused by impacting. We suggest that this depression could be a caldera and is once a possible vent responsible for the emplacement of surrounding lava flows. The long history of volcanic activities in this region makes it an ideal area to study the lunar nearside volcanism and thermal evolution, and we suggest it as a candidate landing site for China’s future lunar exploration missions.

Ascraeus Mons was one of the first of the Martian volcanoes to be imaged by the High Resolution Stereo Camera (HRSC) experiment onboard the ESA Mars Express spacecraft. These images show much of the volcano at a higher resolution than previously, and details of its lava flows, sinuous rilles, flank vents and tectonic features indicate an unexpected origin for some of these features. We establish the time-stratigraphic sequence for these features, and use a numerical model on HRSC stereo DTMs of the sinuous rilles, and conclude that they were formed by water erosion. Terrestrial analogues for such features are found at Reunion Island and other volcanoes. We then examine the overall structure of the volcano, which is dissimilar to that of large terrestrial volcanoes in important respects, and perform laboratory analogue experiments of its deformation, concluding that the tectonic features were formed by sinking of the volcano into a substratum that was much weaker than the volcanic edifice. An ice-rich substratum melted by a combination of pressure melting and magmatic heating seems the most likely mechanism. Analogous water-escape structures in a similar volcanic situation have been identified at Mt Haddington in the Antarctic. The possible role of a hydrological cycle and a hydrothermal system within the volcano are discussed. Based on field evidence, we propose that much of the broad aprons of lobate flows issuing from the NE and SSW foot of Ascraeus Mons are composed of mudflows rather than lava flows. These different approaches are linked into a coherent history of this volcano. The similarity of Ascraeus Mons to Pavonis Mons and Arsia Mons (though Ascraeus is younger) suggests that some of our conclusions may apply to these volcanoes too.

This study examines a set of lunar domes with very low flank slopes which differ in several respects from the frequently occurring lunar effusive domes. Some of these domes are exceptionally large, and most of them are associated with faults or linear rilles of presumably tensional origin. Accordingly, they might be interpreted as surface manifestations of laccolithic intrusions formed by flexure-induced vertical uplift of the lunar crust (or, alternatively, as low effusive edifices due to lava mantling of highland terrain, or kipukas, or structural features). All of them are situated near the borders of mare regions or in regions characterised by extensive effusive volcanic activity. Clementine multispectral UVVIS imagery indicates that they do not preferentially occur in specific types of mare basalt. Our determination of their morphometric properties, involving a combined photoclinometry and shape from shading technique applied to telescopic CCD images acquired at oblique illumination, reveals large dome diameters between 10 and more than 30 km, flank slopes below 0.9 degrees, and volumes ranging from 0.5 to 50 km(3). We establish three morphometric classes. The first class, In1, comprises large domes with diameters above 25 kin and flank slopes of 0.2 degrees-0.6 degrees, class In2 is made up by smaller and slightly steeper domes with diameters of 1015 kin and flank slopes between 0.4 degrees and 0.9 degrees, and domes of class In3 have diameters of 13-20 km and flank slopes below 0.3 degrees. While the morphometric properties of several candidate intrusive domes overlap with those of some classes of effusive domes, we show that a possible distinction criterion are the characteristic elongated Outlines of the candidate intrusive domes. We examine how they differ from typical effusive domes of classes 5 and 6 defined by Head and Gifford [Head, J.W., Gifford, A., 1980. Lunar mare domes: classification and modes of origin. Moon Planets 22, 235-257], and show that they are likely no highland kipukas due to the absence of spectral contrast to their surrounding. These considerations serve as a motivation for an analysis of the candidate intrusive domes in terms of the laccolith model by Kerr and Pollard [Kerr, A.D., Pollard, D.D., 1998. Toward more realistic formulations for the analysis of laccoliths. J. Struct. Geol. 20(12), 1783-1793], to estimate the geophysical parameters, especially the intrusion depth and the magma pressure, which would result from the observed morphometric properties. Accordingly, domes of class In1 are characterised by intrusion depths of 2.3-3.5 km and magma pressures between 18 and 29 MPa. For the smaller and steeper domes of class In2 the magma intruded to shallow depths between 0.4 and 1.0 km while the inferred magma pressures range from 3 to 8 MPa. Class In3 domes are similar to those of class In1 with intrusion depths of 1.8-2.7 km and magma pressures of 15-23 MPa. As an extraordinary feature, we describe in some detail the concentric crater Archytas G associated with the intrusive dome At1 and discuss possible modes of origin. In comparison to the candidate intrusive domes, terrestrial laccoliths tend to be smaller, but it remains unclear if this observation is merely a selection effect due to the limited resolution of our telescopic CCD images. An elongated outline is common to many terrestrial laccoliths and the putative lunar laccoliths, while the thickness values measured for terrestrial laccoliths are typically higher than those inferred for lunar laccoliths, but the typical intrusion depths are comparable. C) 2009 Elsevier Inc. All rights reserved.

More than 200 venusian channels and valleys have been mapped based on analyses of Magellan SAR images. Sinuous rilles are the most abundant channels among six types of venusian channels, and they are widely distributed on Venus. Morphological characteristics of venusian sinuous rilles include sinuous narrowing reaches, source depressions, and length of several 10s to a few 100s of km. This type of channels is known to exist on the Moon and possibly on Mars. Valley networks on Venus often occur in the vicinity of or in connection to sinuous rilles. Cross-sectional morphologies of sinuous rilles and valley networks are of special importance in discussing their formation processes both qualitatively and quantitatively. We reconstructed cross-sectional profiles of 6 sinuous rilles and 2 valley networks using a new radar clinometric method. Reconstructed cross-sections revealed that floors of the channels and valleys are clearly lower than the surrounding plains. This finding implies that the sinuous rilles and the valley networks have erosional origins. Longitudinal depth profiles of the sinuous rilles show distinct decreasing trends toward the termini. Such decreasing trends of depths are qualitatively in agreement with theoretical models and laboratory experiments of thermal erosion. In order to verify this assertion quantitatively, we conduct simple 1-dimensional model calculations under the assumption that both channel-forming lavas and ground substrate are tholeiitic basalt. For initial lava thicknesses in the range 2–6 m, the model calculations yield good matches to the depth profiles. Estimated duration of lava effusion ranges from several months to a few years. These numerical results support thermal erosion of the sinuous rilles but do not necessarily exclude contributions from mechanical erosion processes. Valley networks seem to have formed under a strong structural control in comparison to sinuous rilles. The valleys vary widely in characteristics of the depth profile and flow directions relative to surface slopes. Therefore valley networks appear to have originated from diverse formation mechanisms.

Arnus Vallis (AV) is a >300-km-long sinuous, rille located on the northeastern flank of the Syrtis Major volcano on Mars. Observational evidence presented here suggests that AV formed as an open lava channel that was at least partly incised into the pre-existing terrain. The lava source area consists of a sub-circular pit at the southwestern end of a 7-km-long straight section of channel. AV trends down slope from this source with an average bottom slope of 0.26% or 0.14°. Width varies from ∼1 km at the source to ∼0.6 km near the distal end, with a mean of 0.76 km. Depth decreases from ∼180 m at the source to ∼25 m near the distal end. The AV terminus is obscured by a large impact crater. We suggest that the material that flowed in AV must have been a relatively high temperature, low viscosity lava dynamically and perhaps compositionally similar to terrestrial komatiite or some lunar basalt lavas. If correct, this finding has implications for the mode of construction of Syrtis Major.

Before spacecraft exploration, facts about the Moon were restricted to information about the lunar orbit, angular momentum and density. Speculations about composition and origin were unconstrained. Naked eye and telescope observations revealed two major terrains, the old heavily cratered highlands and the younger mostly circular, lightly cratered maria. The lunar highlands were thought to be composed of granite or covered with volcanic ash-flows. The maria were thought to be sediments, or were full of dust, and possibly only a few million years old. A few perceptive observers such as Ralph Baldwin (Baldwin 1949) concluded that the maria were filled with volcanic lavas, but the absence of terrestrial-type central volcanoes like Hawaii was a puzzle.

Maps of relatively strong crustal magnetic field anomalies detected at low altitudes with the magnetometer instrument on Lunar Prospector are presented. On the lunar nearside, relatively strong anomalies are mapped over the Reiner Gamma Formation on western Oceanus Procellarum and over the Rima Sirsalis rille on the southwestern border of Oceanus Procellarum. The main Rima Sirsalis anomaly does not correlate well with the rille itself but is centered over an Imbrian-aged smooth plains unit interpreted as primary or secondary basin ejecta. The stronger Reiner Gamma anomalies correlate with the locations of both the main Reiner Gamma albedo marking and its northeastward extension. Both the Rima Sirsalis and the Reiner Gamma anomalies are extended in directions approximately radial to the center of the Imbrium basin. This alignment suggests that Imbrium basin ejecta materials (lying in many cases beneath the visible mare surface) are the sources of the nearside anomalies. If so, then the albedo markings associated with the stronger Refiner Gamma anomalies may be consistent with a model involving magnetic shielding of freshly exposed mare materials from the solar wind ion bombardment. Two regions of extensive magnetic anomalies are mapped in regions centered on the Ingenii basin on the south central farside and near the crater Gerasimovic on the southeastern farside. These regions are approximately antipodal to the Imbrium and Crisium basins, respectively. The Imbrium antipode anomaly group is the most areally extensive on the Moon, while the largest anomaly in the Crisium antipode group is the strongest detected by the Lunar Prospector magnetometer. A consideration of the expected antipodal effects of basin-forming impacts as well as a combination of sample data and orbital measurements on the nearside leads to the conclusion that the most probable sources of magnetic anomalies in these two regions are ejecta materials from the respective impacts. In both regions the strongest individual anomalies correlate with swirl-like albedo markings of the Reiner Gamma class visible on available orbital photography.