James Head

James Head
Brown University · Department of Earth, Environmental and Planetary Sciences

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2,129
Publications
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Introduction

Publications

Publications (2,129)
Article
Full-text available
The surfaces of icy moons are covered by fractures, other tectonic features, and active or ancient remains of cryovolcanism. These observations suggest active or recent tectonics, but there is still much unknown about the specific conditions surrounding the formation of these features. One important process leading to the fracture of the ice shell...
Conference Paper
Full-text available
The SPACEIL Institute has built, tested, and is expected by the time of EGU meeting to have launched a mission to land on the Moon. This mission carries two scientific investigations: a magnetic fields investigation and a laser reflector. The magnetometer on the lander was built by the engineers and scientists at the University of California, Los A...
Article
Lunar floor-fractured craters (FFCs) represent the surface manifestation of a class of shallow crustal intrusions in which magma-filled cracks (dikes) rising to the surface from great depth encounter contrasts in host rock lithology (breccia lens, rigid solidified melt sheet) and intrude laterally to form a sill, laccolith or bysmalith, thereby upl...
Article
The Reull Vallis outflow channel is a segmented system of fluvial valleys which originates from the volcanic plains of the Hesperia Planum region of Mars. Explanation of the formation of the Reull Vallis outflow channel by canonical catastrophic groundwater release models faces difficulties with generating sufficient hydraulic head, requiring unrea...
Poster
Full-text available
Introduction: Space missions to the outer planets of the Solar System are providing new insights into the composition, structure, and behavior of icy moons (e.g., Europa, Ganymede, Enceladus). Icy moons typically contain a rocky interior surrounded by an outer water layer, often around 100 km thick [1, 2]. The uppermost part of this layer (~5-30 km...
Article
On Earth a transitional phase between glacial and interglacial periods is referred to as the paraglacial period. This period immediately postdates glacial retreat and is characterized by ice removal, glacial unloading, and the exposure of steep slopes and large sediment stores. These responses led to the development of a suite of morphologic units...
Conference Paper
Full-text available
Lunar mare surface morphologic structures/features are siginificant keys to understanding of the nature of basaltic lava flow emplacement [1], which carries important information on the deep interior mantle [2]. A type of ring-moat structure, characterized by a nearly circular mound surrounded by a ring depression, was first observed during the Apo...
Article
Areally extensive exposures of intact olivine/pyroxene-enriched rock, as well as feldspar-enriched rock, are found in isolated locations throughout the Martian highlands. The petrogenetic origin(s) of these rock units are not well understood, but some previous studies favored an effusive volcanic origin partly on the basis of distinctive compositio...
Article
We use the global distribution of the steepest slopes on crater walls derived from Mars Orbiter Laser Altimeter profile data to assess the magnitudes of degradational processes with latitude, altitude, and time. We independently confirm that Amazonian polar/high-latitude crater slope modification is substantial, but that craters in the low latitude...
Article
The 492 km-diameter Apollo impact basin post-dates, and is located at the inner edge of, the ∼2240 km-diameter South Pole–Aitken (SPA) basin, providing an opportunity to assess the SPA substructure and lateral heterogeneity. Gravity Recovery and Interior Laboratory gravity data suggest an average crustal thickness on the floor of SPA of ∼20 km and...
Article
Full-text available
This is a review of current knowledge about Earth’s nearest planetary neighbour and near twin, Venus. Such knowledge has recently been extended by the European Venus Express and the Japanese Akatsuki spacecraft in orbit around the planet; these missions and their achievements are concisely described in the first part of the review, along with a sum...
Article
Radar-bright deposits at the poles of Mercury are located in permanently shadowed regions, which provide thermally stable environments for hosting and retaining water ice on the surface or in the near subsurface for geologic timescales. While the areal distribution of these radar-bright deposits is well characterized, their thickness, and thus thei...
Article
We report on a decade of fieldwork designed to determine the conditions required for erosion of Mars-like gully channels in the McMurdo Dry Valleys (MDV) of Antarctica. We have outlined the major factors in the morphological evolution of gullies in the Inland Mixed Zone of the MDV: (1) the distribution of ice sources; (2) the temporal aspects of ic...
Article
The Orientale basin is the youngest and best-preserved multiring impact basin on the Moon, having experienced only modest modification by subsequent impacts and volcanism. Orientale is often treated as the type example of a multiring basin, with three prominent rings outside of the inner depression: the Inner Rook Montes, the Outer Rook Montes, and...
Article
Phobos and Deimos are the only natural satellites of the terrestrial planets, other than our Moon. Despite decades of revolutionary Mars exploration and plans to send humans to the surface of Mars in the 2030's, there are many strategic knowledge gaps regarding the moons of Mars, specifically regarding the origin and evolution of these bodies. Addr...
Article
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 resea...
Article
Lunar irregular mare patches (IMPs) comprise dozens of small, distinctive, and enigmatic lunar mare features. Characterized by their irregular shapes, well-preserved state of relief, apparent optical immaturity, and few superposed impact craters, IMPs are interpreted to have been formed or modified geologically very recently (<~100 Ma; Braden et al...
Article
The MESSENGER mission revealed, for the first time, conclusive evidence of explosive volcanism on Mercury. Several previous works have cataloged the appearance and location of explosive volcanism on the planet using a variety of identifying characteristics, including vent presence and deposit color as seen in multispectral image mosaics. We present...
Article
The observed darkening of water tracks near Don Juan Pond (DJP) as well as the formation of wet patches elsewhere in the McMurdo Dry Valleys is attributed at least partially to deliquescence, a process by which salts absorb atmospheric water vapor and form brine, coupled with liquid-phase growth when the atmospheric relative humidity exceeds the wa...
Conference Paper
Full-text available
An imaging survey of the Moon with a resolution ~0.5 m by the LROC NAC cameras onboard the Lunar Reconnaissance Orbiter [1] allowed us to identify ~3200 scarps in the lunar highlands probably formed by young (<50-100 Ma) thrust faults [2-4]; these discoveries have significantly changed our understanding of the post-mare geological history of the Mo...
Conference Paper
Full-text available
The Luna-Glob landing zone is in the southern sub-polar region within the heavily cratered highlands, near the southern portion of the rim of the South Pole-Aitken (SPA) basin [1], [2]. In the landing zone, numerous large craters (up to 100-120 km in diameter and a few kilometers deep) form a very rough surface at tens of kilometers scale. During t...
Conference Paper
Full-text available
The Luna-Glob landing zone is in the southern sub-polar region within the heavily cratered highlands. The main feature of this area is the southern portion of the rim of the South Pole-Aitken (SPA) basin [1, 2]. The major impact structures, basins, are the main sources of materials that form the megaregolith of the Moon [3], [4] and in the landing...
Article
Full-text available
We report on a newly discovered morphological feature on the lunar surface, here named Ring-Moat Dome Structure (RMDS). These low domes (a few meters to ~20 m height with slopes <5°) are typically surrounded by narrow annular depressions or moats. We mapped about 2,600 RMDSs in the lunar maria with diameters ranging from tens to hundreds of meters....
Article
The nature of the Late Noachian climate of Mars remains one of the outstanding questions in the study of the evolution of martian geology and climate. Despite abundant evidence for flowing water (valley networks and open/closed basin lakes), climate models have had difficulties reproducing mean annual surface temperatures (MAT) > 273 K in order to...
Article
The Mercury Laser Altimeter (MLA) measured surface reflectance, rs, at 1064 nm. On Mercury, most water-ice deposits have anomalously low rs values indicative of an insulating layer beneath which ice is buried. Previous detections of surface water ice (without an insulating layer) were limited to seven possible craters. Here we map rs in three addit...
Article
The Dorsa Argentea Formation (DAF), a set of geomorphologic units covering ∼1.5 million square kilometers in the south circumpolar region of Mars, has been interpreted as the remnants of a large south polar ice sheet that formed near the Noachian-Hesperian boundary and receded in the early Hesperian. Determining the extent and thermal regime of the...
Article
Full-text available
Data from the Gravity Recovery and Interior Laboratory (GRAIL) mission have revealed that ∼98% of the power of the gravity signal of the Moon at high spherical harmonic degrees correlates with the topography. The remaining 2% of the signal, which cannot be explained by topography, contains information about density variations within the crust. Thes...
Article
The ∼1500 km diameter Caloris basin is the largest, most well-preserved impact structure on Mercury. The interior of Caloris contains an enigmatic geological unit at depth subsequently excavated by smaller impacts – low-reflectance material (LRM). LRM is interpreted to be the original basin floor material and be composed of melted and re-crystalliz...
Article
Widespread Amazonian-aged fluvial channels have been mapped proximal to Lyot crater, a ~225 km diameter impact basin in the northern lowlands of Mars. Comparable in area to some Noachian/Hesperian fluvial systems, their morphology differs, being dominated by broad, shallow braided channels. Using new developments in the study of cratering, water in...
Article
Double-layered ejecta (DLE) craters are distinctive among the variety of crater morphologies observed on Mars, but the mechanism by which they form remains under debate. We assess two ejecta emplacement mechanisms: (1) atmospheric effects from ejecta curtain-induced vortices or a base surge and (2) ballistic emplacement followed by a landslide of e...
Article
A global and uniformly distributed spike of secondary impact craters on Phobos with diameters (D) <0.6 km and a portion of craters up to D 2 km were produced by Stickney Crater ejecta, including secondary craters within the surface area of Stickney Crater. The global exposure of Phobos to Stickney secondary impacts was facilitated by the desynchron...
Article
GRAIL gravity observations are combined with morphometric measurements to investigate the evolution of crust/mantle structure in the transition from complex craters to peak-ring basins on the Moon.
Article
The enigmatic Ina feature on the Moon was recently interpreted to represent extrusive basaltic volcanic activity within the past 100 m.y. of lunar history, an extremely young age for volcanism on the Moon. Ina is a 2 × 3 km D-shaped depression that consists of a host of unusual bleb-like mounds surrounded by a relatively optically fresh hummocky an...
Article
In June 2009 the Lunar Reconnaissance Orbiter (LRO) spacecraft was launched to the Moon. The payload consists of 7 science instruments selected to characterize sites for future robotic and human missions. Among them, the Lunar Orbiter Laser Altimeter (LOLA) was designed to obtain altimetry, surface roughness, and reflectance measurements. The prima...
Article
Volcanic eruptions on the Moon take place in conditions of low gravity and negligible atmospheric pressure, very different from those on Earth. These differences lead to characteristic lunar versions of hawaiian and strombolian explosive activity, and to the production of unusual eruption products neither predicted nor observed on Earth in the term...
Article
The present-day martian mean annual surface temperature is well below freezing at all latitudes; this produces a near-surface portion of the crust that is below the freezing point of water for >2 consecutive years (defined as permafrost). This permafrost layer (i.e., the cryosphere) is a few to tens of km thick depending on latitude. Below the base...
Article
Full-text available
Mars was characterized by cataclysmic groundwater-sourced surface flooding that formed large outflow channels and that may have altered the climate for extensive periods during the Hesperian era. In particular, it has been speculated that such events could have induced significant rainfall and caused the formation of late-stage valley networks. We...
Article
Full-text available
The martian Residual South Polar Cap (RSPC) is a 1–10 m thick deposit of permanent CO2 ice perched on the much larger H2O ice cap. The CO2 ice is dissected into mesas by erosional landforms that can be broadly classified as (i) quasi-circular pits, (ii) heart-shaped pits, (iii) linear troughs, and (iv) moats. We use HiRISE (25–50 cm/px) images take...
Article
Using in-situ field measurements, laboratory analyses, and numerical modeling, we test the potential efficacy of thermal stress weathering in the flaking of mm-thick alteration rinds observed on cobbles and boulders of Ferrar Dolerite on Mullins Glacier, McMurdo Dry Valleys (MDV). In particular, we examine whether low magnitude stresses, arising fr...
Article
We present an analysis of two concentrically-fractured depressions on Mars, one in northern Hellas and the second in Galaxias Fossae. Volumetric measurements indicate that ∼2.4 km³ and ∼0.2 km³ of material was removed in order to form the North Hellas and Galaxias depressions. The removed material is inferred to be predominantly water ice. Calorime...
Article
We examine the stratigraphic architecture and mineralogy of the western fan deposit in the Jezero crater paleolake on Mars to reassess whether this fan formed as a delta in a standing body of water, as opposed to by alluvial or debris flow processes. Analysis of topography and images reveals that the stratigraphically lowest layers within the fan h...
Article
The “honeycomb” terrain is a Noachian-aged cluster of ∼7 km wide linear cell-like depressions located on the northwestern floor of Hellas basin, Mars. A variety of origins have been proposed for the honeycomb terrain, including deformation rings of subglacial sediment, frozen convection cells from a Hellas impact melt sheet, a swarm of igneous bath...
Article
The evidence for abundant liquid water on early Mars despite the faint young Sun is a long-standing problem in planetary research. Here we present new ab initio spectroscopic and line-by-line climate calculations of the warming potential of reduced atmospheres on early Mars. We show that the strength of both CO2-H2 and CO2-CH4 collision-induced abs...
Article
Multiring basins, large impact craters characterized by multiple concentric topographic rings, dominate the stratigraphy, tectonics, and crustal structure of the Moon. Using a hydrocode, we simulated the formation of the Orientale multiring basin, producing a subsurface structure consistent with high-resolution gravity data from the Gravity Recover...
Article
Full-text available
The Orientale basin is the youngest and best-preserved major impact structure on the Moon. We used the Gravity Recovery and Interior Laboratory (GRAIL) spacecraft to investigate the gravitational field of Orientale at 3- to 5-kilometer (km) horizontal resolution. A volume of at least (3.4 ± 0.2) × 10[superscript 6] km[superscript 3] of crustal mate...
Article
Significant quantities of shock-induced melt are predicted to form during basin-scale impact events, and may contribute substantially to compositional variation in the lunar crust through differentiation processes. Knowledge of the evolution of impact melt sheets and the cooling and crystallization processes involved is therefore important to under...
Article
Global lunar topographic data derived from ranging measurements by the Lunar Oribter Laser Altimeter (LOLA) onboard LRO mission to the Moon have extremely high vertical precision. We use detrended topography as a means for utilization of this precision in geomorphological analysis. The detrended topography was calculated as a difference between act...
Article
Images obtained during MESSENGER's low-altitude campaign in the final year of the mission provide the highest-spatial-resolution views of Mercury's polar deposits. Images for distinct areas of permanent shadow within 35 north polar craters were successfully captured during the campaign. All of these regions of permanent shadow were found to have lo...
Article
Polygonal ridge networks, also known as boxwork or reticulate ridges, are found in numerous locations and geological contexts across Mars. Distinguishing the morphologies and geological context of the ridge networks sheds light on their potential as astrobiological and mineral resource sites of interest. The most widespread type of ridge morphology...
Article
In the present work, we expose procedures and results from a global scale geologically supervised spectral analysis of 121 impact craters on Mercury, selected on the basis of specific morphologic criteria. Using the capabilities of DFTs developed by PEL researchers at DLR, we combined MASCS spectra from the DLR database with MDIS high-resolution im...
Article
Two competing hypotheses suggest lunar Mg-suite parental melts formed: (1) by shallow-level partial melting of a hybridized source region (containing ultramafic cumulates, plagioclase-bearing rocks, and KREEP), producing a plagioclase-saturated, MgO-rich melt, or (2) when plagioclase-undersaturated, MgO-rich melts were brought to plagioclase satura...
Article
Fluvial features present around impact craters on Mars can offer insight into the ancient martian climate and its relationship to the impact cratering process. The widespread spatial and temporal distribution of surface ice on Mars suggests that the interaction between impact cratering and surface ice could have been a relatively frequent occurrenc...
Article
Slope streaks are enigmatic, actively forming albedo features occurring on slopes in high-albedo, low-thermal-inertia, dust-rich equatorial regions on Mars. They are a specifically martian phenomenon with no direct analogs on the Earth. Their morphology suggests that the streaks are initiated at their upslope tips and propagate down to their termin...
Article
Earth-based radar observations and results from the MESSENGER mission have provided strong evidence that permanently shadowed regions near Mercury's poles host deposits of water ice. MESSENGER's complete orbital image and topographic datasets enable Mercury's surface to be observed and modeled under an extensive range of illumination conditions. Th...
Article
Crater size–frequency analyses have shown that the largest volcanic plains deposits on Mercury were emplaced around 3.7 Ga, as determined with recent model production function chronologies for impact crater formation on that planet. To test the hypothesis that all major smooth plains on Mercury were emplaced by about that time, we determined crater...
Article
High resolution geological mapping aided by imagery and elevation data from the Lunar Reconnaissance Orbiter (LRO) and Kaguya missions has revealed the scientifically rich character of impact melt deposits at two young complex craters: Jackson (71 km) and Tycho (85 km). The morphology and distribution of mapped impact melt units provide several ins...
Article
A new method of determining the thickness of mare basalts on the Moon is introduced that is made possible by high-resolution gravity data acquired from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission. Using a localized multitaper spherical-harmonic analysis, an effective density spectrum is calculated that provides an estimate of th...
Article
We utilize a theoretical analysis of the generation, ascent, intrusion and eruption of basaltic magma on the Moon to develop new insights into magma source depths, supply processes, transport and emplacement mechanisms via dike intrusions, and effusive and explosive eruptions. We make predictions about the intrusion and eruption processes and compa...
Article
We present observations on the morphology and stratigraphy of more than 400 paleolake basins on Mars. We show that there are two distinct classes of Martian paleolake basins: (1) paleolakes fed by regionally integrated valley networks (N = 251), and (2) paleolakes fed by isolated inlet valleys not integrated into broader regional drainage systems (...
Article
Floor-fractured craters are a class of lunar crater hypothesized to form in response to the emplacement of a shallow magmatic intrusion beneath the crater floor. The emplacement of a shallow magmatic body should result in a positive Bouguer anomaly relative to unaltered complex craters, a signal which is observed for the average Bouguer anomaly int...
Article
We calculated topographic gradients over the surface of the Moon at a 25 m baseline using data obtained by the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. The relative spatial distribution of steep slopes can be reliably obtained, although some technical characteristics of the LOLA data...
Article
Early during MESSENGER's orbital mission, the Mercury Dual-Imaging System imaged the landform called hollows on the two craters Dominici and Hopper, using its Wide-Angle Camera with eight narrowband color filters ranging from 433 to 996 nm. An absorption feature centered in the MDIS 629-nm filter is evident in reflectance spectra for Dominici's sou...
Article
Recent modeling studies of the early Mars climate predict a predominantly cold climate, characterized by the formation of regional ice sheets across the highland areas of Mars. Formation of the predicted “icy highlands” ice sheets is coincident with a peak in the volcanic flux of Mars involving the emplacement of the Late Noachian – Early Hesperian...
Article
We define lunar cryptovolcanism as volcanic deposits on the Moon hidden by overlying material. Notably, cryptovolcanism includes both cryptomaria (subsurface extrusive basaltic deposits that are obscured by overlying higher albedo basin and crater ejecta) and earlier candidate extrusives, such as the Mg-suite. Knowledge of the volume and extent of...
Article
Observations of Mars from the surface and from orbit suggest that erosion rates over the last ~3Gyr (the Amazonian) have been as slow as 10-5m/Myr and have been dominated by aeolian processes, while ancient (Noachian) erosion rates may have been orders of magnitude higher due to impact bombardment and fluvial activity. Amazonian-aged glacial deposi...
Article
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 de...
Article
Shallow moonquakes are thought to be of tectonic origin. However, the geologic structures responsible for these moonquakes are unknown. Here, we report sites where moonquakes possibly occurred along young lobate scarps in the Schrödinger basin. Our analysis of Lunar Reconnaissance Orbiter and Chandrayaan-1 images revealed four lobate scarps in diff...