The Mars Orbiter Laser Altimeter (MOLA), an instrument on the Mars Global Surveyor spacecraft, has measured the topography, surface roughness, and 1.064-μm reflectivity of Mars and the heights of volatile and dust clouds. This paper discusses the function of the MOLA instrument and the acquisition, processing, and correction of observations to produce global data sets. The altimeter measurements have been converted to both gridded and spherical harmonic models for the topography and shape of Mars that have vertical and radial accuracies of ~1 m with respect to the planet's center of mass. The current global topographic grid has a resolution of 1/64° in latitude × 1/32° in longitude (1 × 2 km^2 at the equator). Reconstruction of the locations of incident laser pulses on the Martian surface appears to be at the 100-m spatial accuracy level and results in 2 orders of magnitude improvement in the global geodetic grid of Mars. Global maps of optical pulse width indicative of 100-m-scale surface roughness and 1.064-μm reflectivity with an accuracy of 5% have also been obtained.

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Mars Orbiter Laser Altimeter: Experiment summary after the first year of global mapping of Mars

[1] The Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO) is a Facility Instrument (i.e., government-furnished equipment operated by a science team not responsible for design and fabrication) designed, built, and operated by Malin Space Science Systems and the MRO Mars Color Imager team (MARCI). CTX will (1) provide context images for data acquired by other MRO instruments, (2) observe features of interest to NASA's Mars Exploration Program (e.g., candidate landing sites), and (3) conduct a scientific investigation, led by the MARCI team, of geologic, geomorphic, and meteorological processes on Mars. CTX consists of a digital electronics assembly; a 350 mm f/3.25 Schmidt-type telescope of catadioptric optical design with a 5.7° field of view, providing a ∼30-km-wide swath from ∼290 km altitude; and a 5000-element CCD with a band pass of 500–700 nm and 7 μm pixels, giving ∼6 m/pixel spatial resolution from MRO's nearly circular, nearly polar mapping orbit. Raw data are transferred to the MRO spacecraft flight computer for processing (e.g., data compression) before transmission to Earth. The ground data system and operations are based on 9 years of Mars Global Surveyor Mars Orbiter Camera on-orbit experience. CTX has been allocated 12% of the total MRO data return, or about ≥3 terabits for the nominal mission. This data volume would cover ∼9% of Mars at 6 m/pixel, but overlapping images (for stereo, mosaics, and observation of changes and meteorological events) will reduce this area. CTX acquired its first (instrument checkout) images of Mars on 24 March 2006.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2006JE002808

Context Camera Investigation on board the Mars Reconnaissance Orbiter

Results by Neukum et al. (2001) and Ivanov (2001) are combined with crater counts to estimate ages of Martian surfaces. These results are combined with studies of Martian meteorites (Nyquist et al., 2001) to establish a rough chronology of Martian history. High crater densities in some areas, together with the existence of a 4.5 Gyr rock from Mars (ALH84001), which was weathered at about 4.0 Gyr, affirm that some of the oldest surfaces involve primordial crustal materials, degraded by various processes including megaregolith formation and cementing of debris. Small craters have been lost by these processes, as shown by comparison with Phobos and with the production function, and by crater morphology distributions. Crater loss rates and survival lifetimes are estimated as a measure of average depositional/erosional rate of activity.

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Cratering Chronology and the Evolution of Mars

[1] The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is a hyperspectral imager on the Mars Reconnaissance Orbiter (MRO) spacecraft. CRISM consists of three subassemblies, a gimbaled Optical Sensor Unit (OSU), a Data Processing Unit (DPU), and the Gimbal Motor Electronics (GME). CRISM's objectives are (1) to map the entire surface using a subset of bands to characterize crustal mineralogy, (2) to map the mineralogy of key areas at high spectral and spatial resolution, and (3) to measure spatial and seasonal variations in the atmosphere. These objectives are addressed using three major types of observations. In multispectral mapping mode, with the OSU pointed at planet nadir, data are collected at a subset of 72 wavelengths covering key mineralogic absorptions and binned to pixel footprints of 100 or 200 m/pixel. Nearly the entire planet can be mapped in this fashion. In targeted mode the OSU is scanned to remove most along-track motion, and a region of interest is mapped at full spatial and spectral resolution (15–19 m/pixel, 362–3920 nm at 6.55 nm/channel). Ten additional abbreviated, spatially binned images are taken before and after the main image, providing an emission phase function (EPF) of the site for atmospheric study and correction of surface spectra for atmospheric effects. In atmospheric mode, only the EPF is acquired. Global grids of the resulting lower data volume observations are taken repeatedly throughout the Martian year to measure seasonal variations in atmospheric properties. Raw, calibrated, and map-projected data are delivered to the community with a spectral library to aid in interpretation.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2006JE002682

Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on Mars Reconnaissance Orbiter (MRO)

More than three years of high-resolution (1.5-20 m/pixel) photographic observations of the surface of Mars have dramatically changed our view of that planet. Among the most important observations and interpretations derived therefrom are that much of Mars, at least to depths of several kilometers, is layered; that substantial portions of the planet have experienced burial and subsequent exhumation; that layered and massive units, many kilometers thick, appear to reflect an ancient period of large-scale erosion and deposition within what are now the ancient heavily cratered regions of Mars; and that processes previously unsuspected, including gully-forming fluid action and burial and exhumation of large tracts of land, have operated within near-contemporary times. These and many other attributes of the planet argue for a complex geology and complicated history.

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Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission

Although the origin and composition of many units are obscure or controversial, their interpretations are based on objective descriptions of morphologic characteristics visible on Viking photomosaics and images. LOWLAND TERRAIN MATERIALS Consist of all plains-forming units between the highland-lowland boundary scarp and the north edge of the map area, exclusive of materials of the western volcanic assemblage on the Tharsis swell. Northern plains assemblage Materials deposited in widespread sheets on northern plains. Within each formation, members mapped at places on basis of crater density; these contacts are approximately located. Assemblage postdates highland-lowland boundary scarp (Scott, 1979). ARCADIA FORMATION—Forms low-lying plains in Arcadia, Amazonis, and Acidalia Planitiae. Embays highland margins and partly buries outflow channels of Kasei, Shalbatana, Simud, Tiu, and Ares Valles. Members distinguished on basis of morphology, albedo, and crater density; common boundaries of older members mapped arbitrarily at places. Flows with lobate margins and small hills with summit craters visible in many places. High-resolution pictures show that sources of some flows are small cratered cones. Interpretation: Mostly lava flows and small volcanoes Aa5 Member 5—Relatively small areal extent. Dark, fresh-appearing flows; few superposed impact craters. Type area: lat 47° N., long 30° Aa4 Member 4—In Arcadia Planitia underlies member 5 and has similar appearance; one other occurrence in channel system of Chryse Planitia. Type area: lat 45° N., long 175° Aa3 Member 3—Forms smooth plains west of Olympus Mons aureoles; embays both the aureoles and fractured terra of Acheron Fossae. Flow fronts visible in places. Type area: lat 15° N., long 155° Aa2 Member 2—Underlies members 3, 4, and 5 in Arcadia Planitia. Includes many small (<10-km-diameter) structures resembling volcanoes and cinder cones. Curved concentric ridges visible on surfaces of flows. Type area: lat 45° N., long 155° Aa1 Member l—Widespread in Chryse and Amazonis Planitiae. Mare-type (wrinkle) ridges common. Type area: lat 30° N., long 40° MEDUSAE FOSSAE FORMATION—Consists of extensive, relatively flat sheets, generally smooth to grooved and gently undulating; deposits appear to vary from soft to indurated; albedo moderate. Occurs near equator in western part of map area. Total thickness may exceed 3 km Amu Upper member—Discontinuous but widespread deposits extend from south of Olympus Mons westward across Amazonis Sulci to map boundary. Smooth, flat to rolling, light-colored surfaces; sculptured into ridges and grooves in places (as in Medusae Fossae); broadly curved margins, locally serrated. Type area: lat 0° N., long 160°. Interpretation: Nonwelded ash-flow …

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Geologic map of the western equatorial region of mars

The map units are arranged according to their occurrences and associations as outlined in the correlation chart. The origin and composition of many units are obscure or controversial, but their identification is based on objective descriptions of morphologic characteristics visible on Viking images. Many of the units and their type areas occur in equatorial regions (Scott and Tanaka, 1986; Greeley and Guest, 1987); unit symbols, names, and groupings already established there are used here. Northern plains assemblage Materials deposited in widespread sheets on northern plains. Boundaries between rock units commonly not well defined, in places indicated by dashed contact. ARCADIA FORMATION—Smooth, sparsely cratered; lobate fronts visible in places. Embays all neighboring units. (Members 2, 4, and 5 (units Aa 2 , Aa 4, and Aa 5) mapped to south, not present in map area.) Interpretation: Lava flows and sediments from local sources Aa 3 Member 3—Forms isolated patches along edge of map area between long 170° and 180° Aa 1 Member 1—Forms low-lying plains surrounding Alba and Tantalus Fossae Aps SMOOTH PLAINS MATERIAL—Forms two areas of smooth, sparsely cratered plains north of crater Lyot near edge of map area (long 315° to 340°) and near knobby, undivided material at long 193°. Interpretation: Probably of diverse origin, but may primarily consist of eolian deposits VASTITAS BOREALIS FORMATION—Subpolar plains deposits. Type areas designated in western equatorial region (Scott and Tanaka, 1986) Hvm Mottled member—Characterized by high-albedo crater deposits superposed on low-albedo, smooth-plains deposits; occurs along more than half of edge of map area; gradational with other members, particularly with knobby member. Interpretation: Lava flows, possibly erupted from fissures and small volcanoes, or alluvial or eolian deposits. Mottled appearance due either to relatively fresh, light-colored material exposed during impact-crater excavation or to high-albedo eolian debris trapped within crater ejecta Hvg Grooved member—Marked by grooves forming polygonal pattern; polygons commonly 5 to 20 km across; small patch at lat 80° N., long 60° in mouth of Chasma Boreale; eroded on south side. Hvr Ridged member—Scattered occurrences mostly in western longitudes; gradational with knobby, mottled, and smooth members; in places embayed by Arcadia Formation. Ridges about 1 to 2 km wide and several to tens of kilometers long commonly form polygons 5 to 20 km across; ridge patterns in some southern outcrops are arcuate or concentric, as at lat 56° N., long 173°. Interpretation: Degraded lava flows or sediments; ridge pattern may be formed by …

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Geologic map of the polar regions of Mars

The terms ignimbrite and ash flow tuff are used to describe relatively thin but extensive sheets of material interpreted to be of pyroclastic origin and to consist of volcanic ash or pumice fragments. Criteria for distinguishing ignimbrites from other geologic materials are considered, and characteristics observed for rock units interpreted as ignimbrites in Amazonis Planitia are discussed. A series of rock units which are thought to represent ignimbrites have been mapped along an east-west border zone between the highland plateau and lowland plains of Amazonis Planitia. The area is roughly bounded by a triangle whose apices are the volcanoes Apollinaris Patera, Biblis Patera, and Olympus Mons. Attention is given to aspects of general geology, morphology and stratigraphy, and thickness and volume estimates. Correlations with other data are considered and some theoretical aspects of Martian ignimbrite emplacement are discussed.

Ignimbrites of Amazonis Planitia region of Mars.

A global geologic map series of Mars was digitized at high resolution (1846 sq km/pixel) It was found that the surface of Mars is predominantly volcanic A resurfacing history was constructed by estimating the total extent of the geologic units Eolian resurfacing was prevalent during the Late Amazonian Epoch, affecting 49 x 10 to the 6th sq km It was found that resurfacing rates vary according to the absolute-age scheme used and generally decrease with time Resurfacing rates were approximately 1000 sq km/yr during the Middle Noachian Epoch, one hundred to several hundred sq km/yr during the Late Noachian to Late Hesperian Epochs, and tens of sq km/yr or less during the Amazonian Period

The resurfacing history of Mars - A synthesis of digitized, viking-based geology

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.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000JE001352

David H. Scott

Papers

Geologic map of the western equatorial region of mars

Geologic map of the polar regions of Mars

Ignimbrites of Amazonis Planitia region of Mars.

The resurfacing history of Mars - A synthesis of digitized, viking-based geology

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