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D. H. Scott

Publications and source records attributed to D. H. Scott.

At least 19 recordsLinked to original sources
USGS2010

Lunar basin formation and highland stratigraphy

Multiring impact basins, formed after solidification of the lunar crust, account for most or all premare regional deposits and structures expressed in the lunar landscape and for major topographic and gravity variations. A fresh basin has two or more concentric mountain rings, a lineated ejecta blanket, and secondary impact craters. Crackled material on the floor may be impact melt. The ejecta blanket was emplaced at least partly as a ground‐hugging flow and was probably hot. A suggested model of basin formation is that the center lifts up and the rings form by inward collapse during evisceration. The resulting basin is shallow and has a central uplift of the mantle. This results in a central gravity high and a ring low. Later flooding by mare basalt has since modified most near side basins. Highland deposits of plains, furrowed and pitted terrain, and various hills, domes, and craters that were interpreted before the Apollo missions as being volcanic can now be interpreted as being basin related. A province map of the whole moon shows that the relatively young Orientale and Imbrium basins imprinted and rejuvenated much of the moon's surface; older basins must have also. The most primitive cratered surface remaining is mostly on the far side, distant from Imbrium and Orientale and other large relatively young basins. All five lunar landings in the highlands sampled stratigraphic units probably related to basins. Several nearly obliterated basins have been discovered recently, including a deep one on the far side that is as wide as the moon's radius. The presence of these ancient basins suggests that the surface is effectively saturated by basins and that many others were completely destroyed by later impacts. Basin impacts may have churned the lunar crust to large depths.

Reviews of Geophysics and Space Physics↗
USGS2001

Latent outflow activity for western Tharsis, Mars: Significant flood record exposed

Observations permitted by the newly acquired Mars Observer Laser Altimeter data have revealed a system of gigantic valleys northwest of the huge Martian shield volcano, Arsia Mons, in the western hemisphere of Mars (northwestern slope valleys (NSVs)). These features, which generally correspond spatially to gravity lows, are obscured by veneers of materials including volcanic lava flows, air fall deposits, and eolian materials. Geologic investigations of the Tharsis region suggest that the system of gigantic valleys predates the construction of Arsia Mons and its extensive associated lava flows of mainly late Hesperian and Amazonian age and coincides stratigraphically with the early development of the outflow channels that debouch into Chryse Planitia. Similar to the previously identified outflow channels, which issued tremendous volumes of water into topographic lows such as Chryse Planitia, the NSVs potentially represent flooding of immense magnitude and, as such, a source of water for a northern plains ocean.

Journal of Geophysical Research E: Planets↗
USGS2001

Ancient drainage basin of the Tharsis region, Mars: Potential source for outflow channel systems and putative oceans or paleolakes

Paleotopographic reconstructions based on a synthesis of published geologic information and high-resolution topography, including topographic profiles, reveal the potential existence of an enormous drainage basin/aquifer system in the eastern part of the Tharsis region during the Noachian Period. Large topographic highs formed the margin of the gigantic drainage basin. Subsequently, lavas, sediments, and volatiles partly infilled the basin, resulting in an enormous and productive regional aquifer. The stacked sequences of water-bearing strata were then deformed locally and, in places, exposed by magmatic-driven uplifts, tectonic deformation, and erosion. This basin model provides a potential source of water necessary to carve the large outflow channel systems of the Tharsis and surrounding regions and to contribute to the formation of putative northern-plains ocean(s) and/or paleolakes.

Journal of Geophysical Research E: Planets↗
USGS2000

System of gigantic valleys northwest of Tharsis, Mars: Latent catastrophic flooding, northwest watershed, and implications for northern plains ocean

Mars Orbiter Laser Altimeter (MOLA) reveals a system of gigantic valleys to the northwest of the huge martian shield volcano, Arsia Mons, in the western hemisphere of Mars. These newly identified northwestern slope valleys (NSVs) potentially signify previously undocumented martian catastrophic floods and may corroborate the northern ocean hypotheses. These features, which generally correspond spatially to gravity lows, were previously obscurred in Mariner and Viking Orbiter imagery by veneers of materials, including volcanic lava flows and air fall deposits. Geologic investigations of the Tharsis region suggest that the NSVs were mainly carved prior to the construction of Arsia Mons and its associated Late Hesperian and Amazonian age lava flows, concurrent with the early development of the outflow channels that debouch into Chryse Planitia.

Geophysical Research Letters↗
USGS1995

Geologic and topographic maps of the Elysium Paleolake basin, Mars

These geologic and topographic maps show a basin in the Elysium region of Mars that is thought to have been the site of a large paleolake during the most recent period (Amazonian) in Mars’ history (Scott and Chapman, 1991b). The basin, referred to as the Elysium basin, extends for more than 2,000 km across the lowland plains (fig. 1). It is important, not only geologically, but because the amount, location, and duration of liquid water that it may have contained would have been critical factors governing the possible origin and survival of life on Mars. The Elysium basin is the only large depositional basin on Mars where direct evidence, both geologic and topographic, of former water levels and spillways has been found. However, indications of possible paleoshorelines have been observed in several other areas along the highland-lowland boundary (described under Geologic and Physiographic Setting; Parker and others, 1989; De Hon and Pani, 1992; Scott and others, 1992). Our study of the Elysium basin had two objectives, to determine (1) the maximum extent of the basin and (2) the former volume of water in the basin and the sources of this water. To fulfill these objectives, we have compiled this sets of maps. The geologic maps shows the source channels and circumbasin materials, and the topographic map of the paleolake, on a new topographic base, shows former shorelines and drainage channels.

IMAP↗
USGS1995

Map of Mars showing channels and possible paleolake basins

The significance of water in the geologic evolution of Mars was strikingly revealed by Mariner and Viking spacecraft images. Theoretical and conceptual models of the Martian climate through time range from a brief, early, warm, and wet period followed by protracted desertification to episodic oceans that inundated the northern lowland plains and produced temperate climatic regimes.

IMAP↗
USGS1992

Geologic map of the Elysium region of Mars

The region centered at Elysium Mons contains that second largest volcanic complex on Mars, surpassed in size by only the Tharsis complex. The Elysium region also has been a center of tectonic, fluvial , and mass-wasting activity. After degradation of ancient cratered terrain within the northern lowlands, volcanic rocks erupted from Elysium Mons, Hecta s Tholus, and Albor Tholus in Elysium Planitia. The volcanic activity was associated with episodes of channel formation, faulting, and apparent volcano/ground-ice modifications of some areas . On this map sheet we portray, describe, and interpret the rich geologic history of the region.

IMAP↗
USGS1991

Martian paleolakes and waterways: Exobiological implications

The problems of how warm and wet Mars once was and when climate transitions may have occurred are not well understood. Mars may have had an early environment similar to Earth's that was conductive to the ermergence of life. In addition, increasing geologic evidence indicates that water, upon which terrestrial life depends, has been present on Mars throughout its history. This evidence suggests that life could have developed not only on early Mars but also over longer periods of time in longer lasting, more clement local environments. Indications of past or present life most likely would be found in areas where liquid water existed in sufficient quantities to provide for the needs of biological systems. We suggest that paleolakes may have provided such environments. Unlike the case on Earth, this record of the origin and evolution of life has probably not been erased by extensive deformation of the Martian surface. Our work has identified eleven prospective areas where large lacustrine basins may once have existed. These areas are important for future biological, geological, and climatological investigations. ?? 1991 Kluwer Academic Publishers.

Origins of Life and Evolution of the Biosphere↗
USGS1991

Geologic map of the Valles Marineris region, Mars

The Valles Marineris region lies east of Thar sis Montes (which extend from lat 12 ˚ to 16˚., long 101 ˚ to 125˚). Part of the region is in the midst of a vast plateau bounded on the west and east by Claritas and Nectaris Fossae, respectively; the remainder extends farther east into southern Xanthe Terr and western Margar itifer Terra. Channel trends, stereophotogrammetry , and radar altimetery indicate that the surface north and east of the canyons sl o pes toward Chryse Planitia ( centered at about lat 25˚ N., long 45˚). Within the broad Valles Marineris region, three distinct physiographic provinces are recognized (fig. 1): (1) the Noctis Labyrithus province, consisting of a high plateau cut by a network of structurally controlled troughs; (2) the Valles Marineris province, characterized by broad, linear valleys hundreds of thousands of kilometer s long; (3) the eastern canyon province , containing irregular depressions as much as 900 km across. Topography has been determined from a preliminary stereophotogrammetric map having a contour interval and a precision of about 1 km (Wu and others, 1986) and from latitudinal tracks of radar altimetry have a pre cision of 200 m (Roth and others, 1980).

IMAP↗
USGS1991

Geologic map of science study area 2, north Kasei Valles, Mars (MTM 25072 Quadrangle)

This map is one in a series of 1:500,000-scale geologic maps initiated by the National Aeronautics and Space Administration to investigate areas of particular scientific interest on Mars. The north Kasei Valles area (fig. 1) merits detailed geologic study because it c ontains part of a large channel system whose age can be determined relative to geologic units that range in age from early intermediate (Early Hesperian) to the very late (Late Amazonian) periods of Martian history . Also, many geomorphic features in the map area suggest changes in water level and multiple erosional events associated with the Kasei Valles system. Later erosional events are indicative of spring sapping ; small-scale, ground-water runoff; and water-mobilized debris flow. Therefore, this large-scale mapping has increased our understanding of the history of hydrolo gic processes on Mars (Chapman and Scott, 1989). For these reasons, part of the area is a candidate site for a sample-return mission to the planet.

IMAP↗
USGS1987

Geologic map of the polar regions of Mars

These geologic maps of the north and south polar regions of Mars, extend ing to 55 ˚ north and south latitudes, overlap by 2 ˚ the geologic maps of the western and eastern regions, which extend to lat ± 57 ˚ . The maps were compiled from Viking medium-resolution photomosaics at scales of 1:2,000,000 and from higher resolution Viking images. The quality and resolution of the Viking pictures are superior to those of Mariner 9 used to prepare the previous maps (Scott and Carr , 1978) that includes these two regions. Because of the Viking orbital configuration, a vast number of high-resolution images of the area within 10 ˚ of the north pole was obtained, whereas many areas in lower northern latitudes were covered only by low-resolution images. In contrast, the south polar region is nearly completely covered by images at medium resolution but is not image d at high resolution.

IMAP↗
USGS1986

Geologic map of the western equatorial region of Mars

The r egional topographic swell centered in the Tharsis Montes and Syria Planum extends over one-third of the map area (U.S. Geological Survey, 1976). Within this high region are the four largest and youngest volcanoes on Mars: Olympus Mons, Arsia Mons, Pavonis Mons, and Ascrae us Mons. The latter three collectively form the large northeast-trending, volcanic mountain chain of the Tharsis Montes. This volcanic chain lies athwart the global highland - lowland boundary that transects the western equatorial region. The boundary, where not covered b young lava flow s, is marked by a gentle, irregular scarp bordered by clusters of low knobby hills. It separates the relatively smooth, flat, spar sely cratered northern plains from the higher, rougher, more densely cratered plateau terrain of the southern highlands . A vast system of canyons, the Valles Marineris , originates in Noctis Labyrinthus , just east of the Tharsis -Sy ria swell, and extends eastward for several thousand kilo meters. Ancient rivers channels appear to have sources in canyons and chaotic terrain north of Valles Ma rineris and in a large fissure at the head of the Mangala V alles. Visible remnants of large circular basins are not as common on Mars as on the Moon, probably because of more active erosion and deeper burial on Mars by eolian and fluvial activity and by widespread volcanism on both the highlands and plains. The youngest and b est preserved impact basin on Mars, lying in the western hemisphere , is more than 1,00 0 km across. It has a broad flat floor ( Argyre Planitia) covered by eolian materials and volcanic flows ; the floor is several kilometers below its encompassing rough mountainous rim.

IMAP↗
USGS1985

Global geologic mapping of Mars: The western equatorial region

Global geologic mapping of Mars was originally accomplished following acquisition of orbital spacecraft images from the Mariner 9 mission. The mapping program represented a joint enterprise by the U.S. Geological Survey and other planetary scientists from universities in the United States and Europe. Many of the Mariner photographs had low resolution or poor albedo contrast caused by atmospheric haze and high-sun angles. Some of the early geologic maps reflect these deficiencies in their poor discrimination and subdivision of rock units. New geologic maps made from higher resolution and better quality Viking images also represent a cooperative effort, by geologists from the U.S. Geological Survey, Arizona State University, and the University of London. This second series of global maps consists of three parts: 1) western equatorial region, 2) eastern equatorial region, and 3) north and south polar regions. These maps, at 1:15 million scale, show more than 60 individual rock-stratigraphic units assigned to three Martian time-stratigraphic systems. The first completed map of the series covers the western equatorial region of Mars. Accompanying the map is a description of the sequence and distribution of major tectonic, volcanic, and fluvial episodes as recorded in the stratigraphic record. ?? 1985.

Advances in Space Research↗
USGS1981

Mars: Paleostratigraphic restoration of buried surfaces in Tharsis Montes

Volcanism in the Tharsis province of Mars occurred in several different areas and was generally continuous without large time intervals between eruptive episodes. Major lava flow units are numerous and extensive, but relatively thin. In many places, impact craters on buried surfaces project above younger flows that overlie them. A new application of crater dating methods has been developed to aid in the identification of these buried surfaces and to determine their lateral extent. The technique is especially adaptable to the Tharsis region where the stratigraphic succession of major flow units has been established by detailed geologic mapping. Knowledge of the overall stratigraphy allows correlations to be made between known and unknown surfaces by comparing their crater frequencies at diameters large enough to insure their recognition on the buried unit. The method has been applied to aid in the restoration of buried rock units and to construct a series of paleostratigraphic maps showing the sequence of major eruptive events in the Tharsis region.

Icarus↗