Geology topics

Research about Mars

Source-linked reports with geographic coverage including Mars.

At least 127 records · Page 7Linked to original sources

USGS2013

Mechanical properties of simulated Mars materials: gypsum-rich sandstones and lapilli tuff

Observations by the Mars Exploration Rover (MER) Opportunity, and other recent studies on diagenesis in the extensive equatorial layered deposits on Mars, suggest that the likely lithologies of these deposits are gypsum-rich sandstones and tuffaceous sediments (for example, Murchie and others, 2009; Squyres and others, 2012; Zimbelman and Scheidt, 2012). Of particular interest is how the diagenesis history of these sediments (degree of cementation and composition) influences the strength and brittle behavior of the material. For instance, fractures are more common in lower porosity materials under strain, whereas deformation bands, characterized by distributed strain throughout a broader discontinuity in a material, are common in higher porosity sedimentary materials. Such discontinuities can either enhance or restrict fluid flow; hence, failure mode plays an important role in determining the mechanics of fluid migration through sediments (Antonellini and Aydin, 1994; 1995; Taylor and Pollard, 2000; Ogilvie and Glover, 2001). As part of a larger study to characterize processes of fault-controlled fluid flow in volcaniclastic and gypsum-rich sediments on Mars, we have completed a series of laboratory experiments to focus on how gypsum clast content and degree of authigenic cementation affects the strength behavior of simulated Mars rocks. Both axial deformation and hydrostatic pressure tests were done at room temperature under dry conditions.

Open-File Report↗

USGS2012

Hydrous carbonates on Mars?: Evidence from Mariner 6/7 infrared spectrometer and ground‐based telescopic spectra

Absorption features at 2.28 and 5.4 μm identified in Mariner 6/7 infrared spectrometer and terrestrial telescopic spectra are consistent with the spectra of hydrous magnesium carbonates such as hydromagnesite and artinite. Spectral characteristics of these hydrous carbonates are different from those of the anhydrous carbonates, as the former do not have the strong spectral features typically associated with anhydrous carbonates such as calcite and siderite. Theoretical mixing indicates that, depending on the type of hydrous carbonate, 10–20 wt % can be incorporated into the regolith without contradicting the spectral observations or the Viking x ray fluorescence chemical analysis. Hydrous carbonates form as weathering products of mafic minerals in the presence of H 2 O and CO 2 , even in the Antarctic. Their formation as evaporite minerals from either original magmas or hydrothermally altered rocks is consistent with the Martian environment, provided liquid water is or has been at least transiently present. On Earth, formation of hydrous Mg carbonates is associated with the production of amorphous iron oxides, which is consistent with both the environment and the inferred surface mineralogy of Mars. These minerals are about 60 wt % H 2 O, CO 3 , and OH; if they are abundant everywhere at the 10% level, then about 6% of the surface weight could be volatiles bound in this type of mineral. Although the stability of hydrous carbonates in a Martian environment is uncertain, there may be kinetic factors inhibiting the dehydration of these minerals, which may persist metastably in the current environment. Although the spectroscopic evidence for anhydrous carbonates is scant, the possible presence of hydrous carbonates provides an appealing mechanism for the existence of carbonates on Mars.

Journal of Geophysical Research↗

USGS2012

Tectonic history of the Syria Planum province of Mars

We attribute most of the development of extensive fractures in the Tharsis region to discrete tectonic provinces within the region, rather than to Tharsis as a single entity. One of these provinces is in Syria Planum. Faults and collapse structures in the Syria Planum tectonic province on Mars are grouped into 13 sets based on relative age, areal distribution, and morphology. According to superposition and fault crosscutting relations and crater counts we designate six distinct episodes of tectonic activity in the following chronologic order: stage I is an early to late Noachian deformation forming mostly east-west structures (fault set IA); some large volcanoes also formed. Faults were produced possibly by flexural uplift. Also, arcuate, north trending grabens (set IB) indicate that faulting is transitional to the next stage. Stage II is late Noachian to early Hesperian radial faulting centered in Syria Planum, possibly due to isostatic uplift in late Noachian (set IIA) to early Hesperian (set IIB) time. Stage III is early to late Hesperian faulting tangential to Syria Planum that was related to local centers of uplift (sets III1-III3) on the periphery of Syria Planum. Stage IV is a late Hesperian graben formation that was circumferential to Syria Planum (set IVA), caused either by collapse associated with eruption of magma or by flexure of the lithosphere due to volcanic loading. In association with volcanism, minor faulting occurred, producing an oval pattern of faults in southwest Syria Planum (set IVBl) and a radial pattern south of the planum (set IVB2) that apparently rejuvenated buried stage II faults. Stage V is a late Hesperian to early Amazonian development of grabens and troughs of Noctis Labyrinthus and western Valles Marineris (set V) that was probably instigated by local uplift; exposure of groundwater or ground ice zones may have produced further collapse and trough enlargement. Stage VI is early Amazonian northwest trending faulting in Noctis Fossae (set VIl), perhaps due to Tharsis Monies-centered tectonism, and north northwest normal faulting along the eastern side of the Claritas rise (set VI2) that was due to tectonic subsidence. The duration of tectonic activity in the Syria Planum province was perhaps 2–3 b.y. Photoclinometric topographic profiles across 132 grabens and fault scarps show that Syria Planum grabens have widths (average of 2.5 km, and most range from 1 to 6 km) similar to lunar grabens, but the Martian grabens have slightly higher side walls (average about 132 m) and gentler wall slopes (average of 9° and range of 2°–25°) than lunar grabens (93 m high and 18° slopes). Scarp degradation on Mars has progressed through quakes, impact shaking, and dry slope processes; the lower slopes may be due to Mars’ higher gravity. Estimates of the amount of extension for individual grabens range from 20 to 350 m; most estimates of the thickness of the faulted layer range from 0.5 to 4.5 km (average is 1.5 km). This thickness range corresponds closely to the 0.8-to 3.6-km range in depth for pits, troughs, and canyons in Noctis Labyrinthus and along the walls of Valles Marineris. We propose that the predominant 1-to 1.5-km values obtained for both the thickness of the faulted layer and the depths of the pits, troughs, and theater heads of the canyons reflect the initial depth to the water table in this region, as governed by the depth to the base of ground ice. Maximum depths for these features may indicate lowered groundwater table depths and the base of ejecta material.

Journal of Geophysical Research Solid Earth↗

USGS2012

Infrared spectra and crystal chemistry of scapolites: implications for Martian mineralogy

Near‐infrared and midinfrared spectra of a wide range of scapolite compositions were studied to determine the cause of the 2.36‐μm features that have been correlated with similar features in the near‐IR spectrum of Mars. We attribute the 2.36−μm features to vibrations caused by HCO 3 − and HSO 4 − in the anion sites of scapolite. The 2.36‐μm absorption complex consists of four overlapping bands with the following assignments: absorptions at 2.33 and 2.35 μm are attributed to combinations of hydroxyl stretches and a O‐H … O bend from HCO 3 − , absorptions at 2.39 and 2.41 μm are attributed to combinations of hydroxyl stretches and a O‐H ··· O bend from HSO 4 − . The relative intensities of all four bands vary according to the HCO 3 − /HSO 4 − ratio and disordered anion site occupancy. Oriented single‐crystal polarized spectra of a bicarbonate‐bisulfate bearing scapolite show that the 3.9‐μm hydrogen bond stretch, from HCO 3 − , is polarization controlled. This verifies that HCO 3 − is an intimate part of the scapolite crystal structure and that hydrogen in HCO 3 − is forming hydrogen bonds with T 1 framework oxygens. The association of yellow fluorescence, attributed to S 2 − in the anion site, with vibrational features of HCO 3 − and HSO 4 − in the rims and fractures of scapolite grains suggests that some common geochemical process is incorporating these ions into the crystal structure during later stage alteration of scapolite. The positional disorder of HCO 3 − and HSO 4 − in the low‐symmetry anion site of scapolite gives the 2.36‐μm band complex a unique spectral signature not likely to be duplicated in any other mineral.

Journal of Geophysical Research↗

USGS2012

Selection of the Mars Science Laboratory landing site

The selection of Gale crater as the Mars Science Laboratory landing site took over five years, involved broad participation of the science community via five open workshops, and narrowed an initial >50 sites (25 by 20 km) to four finalists (Eberswalde, Gale, Holden and Mawrth) based on science and safety. Engineering constraints important to the selection included: (1) latitude (±30°) for thermal management of the rover and instruments, (2) elevation (<-1 km) for sufficient atmosphere to slow the spacecraft, (3) relief of <100-130 m at baselines of 1-1000 m for control authority and sufficient fuel during powered descent, (4) slopes of <30° at baselines of 2-5 m for rover stability at touchdown, (5) moderate rock abundance to avoid impacting the belly pan during touchdown, and (6) a radar-reflective, load-bearing, and trafficable surface that is safe for landing and roving and not dominated by fine-grained dust. Science criteria important for the selection include the ability to assess past habitable environments, which include diversity, context, and biosignature (including organics) preservation. Sites were evaluated in detail using targeted data from instruments on all active orbiters, and especially Mars Reconnaissance Orbiter. All of the final four sites have layered sedimentary rocks with spectral evidence for phyllosilicates that clearly address the science objectives of the mission. Sophisticated entry, descent and landing simulations that include detailed information on all of the engineering constraints indicate all of the final four sites are safe for landing. Evaluation of the traversabilty of the landing sites and target “go to” areas outside of the ellipse using slope and material properties information indicates that all are trafficable and “go to” sites can be accessed within the lifetime of the mission. In the final selection, Gale crater was favored over Eberswalde based on its greater diversity and potential habitability.

Space Science Reviews↗

USGS2012

Curiosity's Mars Hand Lens Imager (MAHLI) investigation

The Mars Science Laboratory (MSL) Mars Hand Lens Imager (MAHLI) investigation will use a 2-megapixel color camera with a focusable macro lens aboard the rover, Curiosity, to investigate the stratigraphy and grain-scale texture, structure, mineralogy, and morphology of geologic materials in northwestern Gale crater. Of particular interest is the stratigraphic record of a ?5 km thick layered rock sequence exposed on the slopes of Aeolis Mons (also known as Mount Sharp). The instrument consists of three parts, a camera head mounted on the turret at the end of a robotic arm, an electronics and data storage assembly located inside the rover body, and a calibration target mounted on the robotic arm shoulder azimuth actuator housing. MAHLI can acquire in-focus images at working distances from ?2.1 cm to infinity. At the minimum working distance, image pixel scale is ?14 μm per pixel and very coarse silt grains can be resolved. At the working distance of the Mars Exploration Rover Microscopic Imager cameras aboard Spirit and Opportunity, MAHLI?s resolution is comparable at ?30 μm per pixel. Onboard capabilities include autofocus, auto-exposure, sub-framing, video imaging, Bayer pattern color interpolation, lossy and lossless compression, focus merging of up to 8 focus stack images, white light and longwave ultraviolet (365 nm) illumination of nearby subjects, and 8 gigabytes of non-volatile memory data storage.

Space Science Reviews↗

USGS2012

Surface properties of the Mars Science Laboratory candidate landing sites: characterization from orbit and predictions

This work describes the interpretation of THEMIS-derived thermal inertia data at the Eberswalde, Gale, Holden, and Mawrth Vallis Mars Science Laboratory (MSL) candidate landing sites and determines how thermophysical variations correspond to morphology and, when apparent, mineralogical diversity. At Eberswalde, the proportion of likely unconsolidated material relative to exposed bedrock or highly indurated surfaces controls the thermal inertia of a given region. At Gale, the majority of the landing site region has a moderate thermal inertia (250 to 410 J m -2 K -1 s -1/2 ), which is likely an indurated surface mixed with unconsolidated materials. The primary difference between higher and moderate thermal inertia surfaces may be due to the amount of mantling material present. Within the mound of stratified material in Gale, layers are distinguished in the thermal inertia data; the MSL rover could be traversing through materials that are both thermophysically and compositionally diverse. The majority of the Holden ellipse has a thermal inertia of 340 to 475 J m -2 K -1 s -1/2 and consists of bed forms with some consolidated material intermixed. Mawrth Vallis has a mean thermal inertia of 310 J m -2 K -1 s -1/2 and a wide variety of materials is present contributing to the moderate thermal inertia surfaces, including a mixture of bedrock, indurated surfaces, bed forms, and unconsolidated fines. Phyllosilicates have been identified at all four candidate landing sites, and these clay-bearing units typically have a similar thermal inertia value (400 to 500 J m -2 K -1 s -1/2 ), suggesting physical properties that are also similar.

Space Science Reviews↗

USGS2012

Seasonal activity and morphological changes in martian gullies

Recent studies of martian dune and non-dune gullies have suggested a seasonal control on present-day gully activity. The timing of current gully activity, especially activity involving the formation or modification of channels (which commonly have been taken as evidence of fluvial processes), has important implications regarding likely gully formation processes and necessary environmental conditions. In this study, we describe the results of frequent meter-scale monitoring of several active gully sites by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO). The aim is to better assess the scope and nature of current morphological changes and to provide improved constraints on timing of gully activity on both dune and non-dune slopes. Our observations indicate that (1) gully formation on Mars is ongoing today and (2) the most significant morphological changes are strongly associated with seasonal frost and defrosting activity. Observed changes include formation of all major components of typical gully landforms, although we have not observed alcove formation in coherent bedrock. These results reduce the need to invoke recent climate change or present-day groundwater seepage to explain the many martian gullies with pristine appearance.

Icarus↗

USGS2012

Ancient impact and aqueous processes at Endeavour Crater, Mars

The rover Opportunity has investigated the rim of Endeavour Crater, a large ancient impact crater on Mars. Basaltic breccias produced by the impact form the rim deposits, with stratigraphy similar to that observed at similar-sized craters on Earth. Highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits. Gypsum-rich veins cut sedimentary rocks adjacent to the crater rim. The gypsum was precipitated from low-temperature aqueous fluids flowing upward from the ancient materials of the rim, leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate-rich sandstones of the Meridiani region.

Science↗

USGS2012

An atlas of Mars sedimentary rocks as seen by HiRISE

Images of distant and unknown places have long stimulated the imaginations of both explorers and scientists. The atlas of photographs collected during the Hayden (1872) expedition to the Yellowstone region was essential to its successful advocacy and selection in 1872 as America’s first national park. Photographer William Henry Jackson of the Hayden expedition captured the public’s imagination and support, returning home with a treasure of images that confirmed the existence of western landmarks previously regarded as glorified myths: the Grand Tetons, Old Faithful, and strange pools of boiling hot mud. Fifty years later, photographer Ansel Adams began his long legacy of providing the public with compilations of iconic images of natural wonders that many only see in prints. Photography in space has provided its own bounty. Who can forget the first image of Earthrise taken by astronaut William Anders in 1968 from Apollo 8; the solemnity of the first photos of the surface of the Moon from the Apollo 11 astronauts; and the startling discovery of the tallest mountain in the solar system (Olympus Mons) on the surface of Mars in images sent from Mariner 9? The images from Mariner 9 also allowed for a game-changing discovery. Earlier, based on very limited Mariner 4 data that covered less than 10% of the planet’s surface, Chapman et al. (1968) speculated that “If substantial aqueous erosion features—such as river valleys— were produced during earlier epochs of Mars, we should not expect any trace of them to be visible.

Book chapter↗

USGS2012

Duststones on Mars: Source, transport, deposition and erosion

Dust is an abundant material on Mars, and there is strong evidence that it is a contributor to the rock record as “duststone,” analogous in many ways to loess on Earth. Although a common suite of dust formation mechanisms has operated on the two planets, fundamental differences in environments and geologic histories have resulted in vastly different weighting functions, causing distinct depositional styles and erosional mechanisms. On Earth, dust is derived predominantly from glacial grinding and, in nonglacial environments, by other processes, such as volcanism, eolian abrasion, and fluvial comminution. Hydrological and biological processes convert dust accumulations to loess deposits. Active hydrology also acts to clean dust from the atmosphere and convert loess into soil or erode it entirely. On Mars, glacial production of dust has been minor, with most fine particles probably produced from ancient volcanic, impact, and fluvial processes. Dust is deposited under arid conditions in which aggregate growth and cementation are the stabilizing agents. Thick accumulations result in duststone.

SEPM Special Publication↗

USGS2012

Stratigraphic architecture of bedrock reference section, Victoria Crater, Meridiani Planum, Mars

The Mars Exploration Rover Opportunity has investigated bedrock outcrops exposed in several craters at Meridiani Planum, Mars, in an effort to better understand the role of surface processes in its geologic history. Opportunity has recently completed its observations of Victoria crater, which is 750 m in diameter and exposes cliffs up to ~15 m high. The plains surrounding Victoria crater are ~10 m higher in elevation than those surrounding the previously explored Endurance crater, indicating that the Victoria crater exposes a stratigraphically higher section than does the Endurance crater; however, Victoria strata overlap in elevation with the rocks exposed at the Erebus crater. Victoria crater has a well-developed geomorphic pattern of promontories and embayments that define the crater wall and that reveal thick bedsets (3–7m) of large-scale cross-bedding, interpreted as fossil eolian dunes. Opportunity was able to drive into the crater at Duck Bay, located on the western margin of Victoria crater. Data from the Microscopic Imager and Panoramic Camera reveal details about the structures, textures, and depositional and diagenetic events that influenced the Victoria bedrock. A lithostratigraphic subdivision of bedrock units was enabled by the presence of a light-toned band that lines much of the upper rim of the crater. In ascending order, three stratigraphic units are named Lyell, Smith, and Steno; Smith is the light-toned band. In the Reference Section exposed along the ingress path at Duck Bay, Smith is interpreted to represent a zone of diagenetic recrystallization; however, its upper contact also coincides with a primary erosional surface. Elsewhere in the crater the diagenetic band crosscuts the physical stratigraphy. Correlation with strata present at nearby promontory Cape Verde indicates that there is an erosional surface at the base of the cliff face that corresponds to the erosional contact below Steno. The erosional contact at the base of Cape Verde lies at a lower elevation, but within the same plane as the contact below Steno, which indicates that the material above the erosional contact was built on significant depositional paleotopography. The eolian dune forms exposed in Duck Bay and Cape Verde, combined with the geometry of the erosional surface, indicate that these outcrops may be part of a larger-scale draa architecture. This insight is possible only as a result of the larger-scale exposures at Victoria crater, which significantly exceed the more limited exposures at the Erebus, Endurance, and Eagle craters.

Book chapter↗

USGS2012

Mars global digital dune database: MC-30

The Mars Global Digital Dune Database (MGD 3 ) provides data and describes the methodology used in creating the global database of moderate- to large-size dune fields on Mars. The database is being released in a series of U.S. Geological Survey Open-File Reports. The first report (Hayward and others, 2007) included dune fields from lat 65° N. to 65° S. ( http://pubs.usgs.gov/of/2007/1158/ ). The second report (Hayward and others, 2010) included dune fields from lat 60° N. to 90° N. ( http://pubs.usgs.gov/of/2010/1170/ ). This report encompasses ~75,000 km 2 of mapped dune fields from lat 60° to 90° S. The dune fields included in this global database were initially located using Mars Odyssey Thermal Emission Imaging System (THEMIS) Infrared (IR) images. In the previous two reports, some dune fields may have been unintentionally excluded for two reasons: (1) incomplete THEMIS IR (daytime) coverage may have caused us to exclude some moderate- to large-size dune fields or (2) resolution of THEMIS IR coverage (100 m/pixel) certainly caused us to exclude smaller dune fields. In this report, mapping is more complete. The Arizona State University THEMIS daytime IR mosaic provided complete IR coverage, and it is unlikely that we missed any large dune fields in the South Pole (SP) region. In addition, the increased availability of higher resolution images resulted in the inclusion of more small (~1 km 2 ) sand dune fields and sand patches. To maintain consistency with the previous releases, we have identified the sand features that would not have been included in earlier releases. While the moderate to large dune fields in MGD 3 are likely to constitute the largest compilation of sediment on the planet, we acknowledge that our database excludes numerous small dune fields and some moderate to large dune fields as well. Please note that the absence of mapped dune fields does not mean that dune fields do not exist and is not intended to imply a lack of saltating sand in other areas. Where availability and quality of THEMIS visible (VIS), Mars Orbiter Camera (MOC) narrow angle, Mars Express High Resolution Stereo Camera, or Mars Reconnaissance Orbiter Context Camera and High Resolution Imaging Science Experiment images allowed, we classified dunes and included some dune slipface measurements, which were derived from gross dune morphology and represent the approximate prevailing wind direction at the last time of significant dune modification. It was beyond the scope of this report to look at the detail needed to discern subtle dune modification. It was also beyond the scope of this report to measure all slipfaces. We attempted to include enough slipface measurements to represent the general circulation (as implied by gross dune morphology) and to give a sense of the complex nature of aeolian activity on Mars. The absence of slipface measurements in a given direction should not be taken as evidence that winds in that direction did not occur. When a dune field was located within a crater, the azimuth from crater centroid to dune field centroid was calculated, as another possible indicator of wind direction. Output from a general circulation model is also included. In addition to polygons locating dune fields, the database includes ~700 of the THEMIS VIS and MOC images that were used to build the database.

Open-File Report↗

USGS2012

Geologic map of the north polar region of Mars

The north polar region of Mars occurs within the central and lowest part of the vast northern plains of Mars and is dominated by the roughly circular north polar plateau, Planum Boreum. The northern plains formed very early in Martian time and have collected volcanic flows and sedimentary materials shed from highland sources. Planum Boreum has resulted from the accumulation of water ice and dust particles. Extensive, uncratered dune fields adjacent to Planum Boreum attest to the active and recent transport and accumulation of sand. Our geologic map of Planum Boreum is the first to record its entire observable stratigraphic record using the various post-Viking image and topography datasets released before 2009. We also provide much more detail in the map than previously published, including some substantial revisions based on new data and observations. The available data have increased and improved immensely in quantity, resolution, coverage, positional accuracy, and spectral range, enabling us to resolve previously unrecognized geomorphic features, stratigraphic relations, and compositional information. We also employ more carefully prescribed and effective mapping methodologies and digital techniques, as well as formatting guidelines. The foremost aspect to our mapping approach is how geologic units are discriminated based primarily on their temporal relations with other units as expressed in unit contacts by unconformities or by gradational relations. Whereas timing constraints of such activity in the north polar region are now better defined stratigraphically, they remain poorly constrained chronologically. The end result is a new reconstruction of the sedimentary, erosional, and structural histories of the north polar region and how they may have been driven by climate conditions, available geologic materials, and eolian, periglacial, impact, magmatic, hydrologic, and tectonic activity.

Scientific Investigations Map↗

USGS2012

Candidate cave entrances on Mars

This paper presents newly discovered candidate cave entrances into Martian near-surface lava tubes, volcano-tectonic fracture systems, and pit craters and describes their characteristics and exploration possibilities. These candidates are all collapse features that occur either intermittently along laterally continuous trench-like depressions or in the floors of sheer-walled atypical pit craters. As viewed from orbit, locations of most candidates are visibly consistent with known terrestrial features such as tube-fed lava flows, volcano-tectonic fractures, and pit craters, each of which forms by mechanisms that can produce caves. Although we cannot determine subsurface extents of the Martian features discussed here, some may continue unimpeded for many kilometers if terrestrial examples are indeed analogous. The features presented here were identified in images acquired by the Mars Odyssey's Thermal Emission Imaging System visible-wavelength camera, and by the Mars Reconnaissance Orbiter's Context Camera. Select candidates have since been targeted by the High-Resolution Imaging Science Experiment. Martian caves are promising potential sites for future human habitation and astrobiology investigations; understanding their characteristics is critical for long-term mission planning and for developing the necessary exploration technologies.

Journal of Cave and Karst Studies↗

USGS2011

Planet-wide sand motion on mars

Prior to Mars Reconnaissance Orbiter data, images of Mars showed no direct evidence for dune and ripple motion. This was consistent with climate models and lander measurements indicating that winds of sufficient intensity to mobilize sand were rare in the low-density atmosphere. We show that many sand ripples and dunes across Mars exhibit movement of as much as a few meters per year, demonstrating that Martian sand migrates under current conditions in diverse areas of the planet. Most motion is probably driven by wind gusts that are not resolved in global circulation models. A past climate with a thicker atmosphere is only required to move large ripples that contain coarse grains.

Geology↗

USGS2011

The indication of Martian gully formation processes by slope-area analysis

The formation process of recent gullies on Mars is currently under debate. This study aims to discriminate between the proposed formation processes - pure water flow, debris flow and dry mass wasting - through the application of geomorphological indices commonly used in terrestrial geomorphology. High-resolution digital elevation models (DEMs) of Earth and Mars were used to evaluate the drainage characteristics of small slope sections. Data from Earth were used to validate the hillslope, debris-flow and alluvial process domains previously found for large fluvial catchments on Earth, and these domains were applied to gullied and ungullied slopes on Mars. In accordance with other studies, our results indicate that debris flow is one of the main processes forming the Martian gullies that were being examined. The source of the water is predominantly distributed surface melting, not an underground aquifer. Evidence is also presented indicating that other processes may have shaped Martian crater slopes, such as ice-assisted creep and solifluction, in agreement with the proposed recent Martian glacial and periglacial climate. Our results suggest that, within impact craters, different processes are acting on differently oriented slopes, but further work is needed to investigate the potential link between these observations and changes in Martian climate.

Geological Society Special Publication↗

USGS2011

Field Reconnaissance Geologic Mapping of the Columbia Hills, Mars: Results from MER Spirit and MRO HiRISE Observations

Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclastic materials, mobile fines, and fall deposits, the selective exhumation of deep and well-preserved geologic units has exposed undisturbed outcrops, stratigraphic sections, and structural information much as they are preserved and exposed on Earth. A rich geologic record awaits skilled future field investigators on Mars. The correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map. Most of the outcrops visited are interpreted to be pyroclastic, impactite, and epiclastic deposits overlying an unexposed substrate, probably related to a modified Gusev crater central peak. Fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit. Examination of the rocks exposed above and below the major unconformity between the plains lavas and the Columbia Hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of Mars was a time of more intense deposition and modification of the surface. Although the availability of fluids and the chemical and mineral activity declined from this early period, significant later volcanism and fluid convection enabled additional, if localized, chemical activity.

Journal of Geophysical Research E: Planets↗