Ancient Martian aeolian processes and palaeomorphology reconstructed from the Stimson formation on the lower slope of Aeolis Mons, Gale crater, Mars (original) (raw)
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Journal of Geophysical research, 2003
The sedimentary history of Proctor Crater is described especially with regards to aeolian processes. Proctor Crater is a 150 km diameter crater in Noachis Terra, within the southern highlands of Mars. The analysis leading to the sedimentary history incorporates several data sets including imagery, elevation, composition, and thermal inertia, mostly from the Mars Global Surveyor mission.
Icarus, 2011
High albedo features are identified in association with barchan dunes in an equatorial inter-crater dune field on Mars using images from the MRO mission. This paper describes the morphometric properties of these features and their association with the present barchan dune field. We propose that these features are cemented aeolian deposits that form at the foot of the dune avalanche face. A possible terrestrial analog exists at White Sands National Monument, in south-central New Mexico, USA. The presence of these features suggests past episodes of dune migration in inter-crater dunefields and liquid water in the near sub-surface in sufficient quantity to cause the cementation of aeolian dune sediment.
Icarus, 2011
Gale Crater contains a 5.2 km-high central mound of layered material that is largely sedimentary in origin and has been considered as a potential landing site for both the MER (Mars Exploration Rover) and MSL (Mars Science Laboratory) missions. We have analyzed recent data from Mars Reconnaissance Orbiter to help unravel the complex geologic history evidenced by these layered deposits and other landforms in the crater. Results from imaging data from the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) confirm geomorphic evidence for fluvial activity and may indicate an early lacustrine phase. Analysis of spectral data from the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument shows clay-bearing units interstratified with sulfate-bearing strata in the lower member of the layered mound, again indicative of aqueous activity. The formation age of the layered mound, derived from crater counts and superposition relationships, is $3.6-3.8 Ga and straddles the Noachian-Hesperian time-stratigraphic boundary. Thus Gale provides a unique opportunity to investigate global environmental change on Mars during a period of transition from an environment that favored phyllosilicate deposition to a later one that was dominated by sulfate formation.
Investigating Sedimentary Rocks to Understand Past Wet Climate of Mars
2015
The "deltaic" geomorphology in the Eberswalde Crater is often considered a "smoking gun" for the warm-and-wet ancient climate of Mars. The Crater displays sedimentary features, which many argue, can only be found in a river-delta system (Bhattacharya et al., 2005). However, with the advent of high-resolution images, the Eberswalde Crater delta's geomorphology has been revealed to be more complicated than could be seen previously. These high-resolution data suggest that the development of the Eberswalde delta is likely more episodic (Schieber 2007). While better resolution data has placed doubt on the wet Mars hypothesis at the Eberswalde Crater, the opposite is true of the Gale Crater. Recent images acquired by the Mars Curiosity Rover have revolutionized the hypotheses explaining the formation of Mount Sharp in the Gale Crater. The new prevailing hypothesis is that Mount Sharp was formed by a series of crater lakes (NASA, 2014). This study provides evidence supporting the crater lake hypothesis, using bedding architecture diagrams, facies diagrams, lithologic logs, paleocurrent map and rose diagram, and minimum water depth estimations of the exposed sedimentary layers. Reconstructing a detailed depositional history of the Gale Crater Lake provides a window into a more ancient Mars where life could have evolved in a wet habitable climate that is absent today.
Earth Surface Processes and Landforms, 2012
Sunset Crater in north-central Arizona (USA) is a 900-year-old scoria-cone volcano. Wind action has redistributed its widespread tephra deposit into a variety of aeolian dune forms that serve as a terrestrial analog for similar landforms and aeolian processes on Mars. Fieldwork was conducted to collect essential geomorphological and sedimentological data, and to establish a baseline for the type and morphometry of dunes, physical properties, interactions with topography, and saltation pathways. Our analyses focused primarily on coppice dunes, falling dunes, wind ripples, and sand streaks. For all collected volcaniclastic aeolian sediment samples, the sand-size fraction dominated, ranging from almost 100% sand to 74.6% sand. No sample contained more than 1.6% silt. The composition is overwhelmingly basaltic with non-basaltic particles composing 2 to 6% of the total. Coppice (nebkha) dunes form where clumps of vegetation trap saltating particles and create small mounds or hummocks. Mean grain size for coppice dune samples is coarse sand. Measured dune height for 15 coppice dunes ranged from 0.3 to 3.3 m with a mean of 1 m. Mean length was 6.7 m and mean width was 4.8 m. Falling dunes identified in this study are poorly developed and thin, lacking a prominent ramp-like structure. Mean wavelength for three sets of measured ripples ranged from 22 to 36 cm. Sand streaks extend downwind for more than a kilometer and are up to 200 m in width. They commonly occur on the lee side of mesas and similar landforms and are typically the downwind continuation of falling dunes. Falling dunes, wind ripples, and sand streaks have been identified on Mars, while coppice dunes are similar to Martian shadow or lee dunes in which sand accumulates in the lee of obstacles.
Geomorphic Evolution of the Martian Highlands Through Ancient Fluvial Processes
Journal of Geophysical Research, 1993
Craters in the Martian highlands are preserved in various stages of degradation. As a result of an erosional process active from the Middle Noachian (4.40-3.92 b.y.) through the Hesperian (3.55-1.8 b.y.), ejecta associated with fresh impact craters became etched, hummocky, and dissected by rimoff channels. With time, interior gullies became deeply incised and ejecta deposits were entirely removed. Infilling of the craters followed until, in some instances, the craters were completely buried. Only fluvial processes explain these morphologic variations, the size range of affected craters, and the size-frequency distribution curves associated with these crater populations. Based on the number of superposed fresh impact craters, fluvial processes affecting the highlands ceased entirely by the end of the Hesperian. No correlation between cessation of degradation and latitude exists. However, a strong correlation exists between cessation of degradation and elevation. Degradation ended at higher elevations (e.g., 3-4 km; N[5]=~200, Late Noachian) before lower elevations (e.g., 1-2 km; N[5]=~180, Early Hesperian), suggesting that cessation was coupled to desiccation of the volatile reservoir and degassing of a 5-20 bar primordial atmosphere. Volatiles released to the surface by rimoff channel formation and seepage may have been part of a complex hydrologic cycle that included periodic, heavy amounts of precipitation. Rainfall was principally responsible for degrading the highlands, eroding impact craters, and redistributing sediments. Rainfall also recharged the highland aquifers, allowing sapping and seepage to continue for hundreds of millions of years. As the primordial atmosphere was lost, cloud condensation, and thus rainfall and aquifer recharge, occurred at progressively lower elevations. Based on estimates on the amount of material removed and duration of degradation, denudation rates averaged 0.0001-0.005 mm/yr. These rates are equivalent to those in ten'estrial periglacial environments. [Soderblom et al., 1973; Mutch et al., 1977, pp. 138-150]. The comprehensive analysis of the cratered highlands presented here suggests that during the Noachian (4.6 to ~3.5 Ga), surface processes and denudation rates on Mars were similar to those presently occurring in periglacial environments on Earth. Cessation of these processes appears to have been coupled to desiccation of the volatile reservoir and degassing of the early planetary atmosphere. 3453 3454 CRADDOCK AND MAXWF_,LL: ANCIENT FLUVI• PROCESSES ON MARS ß o o • Fig. 1. Shaded relief map of the equatorial region of Mars. Areas outlined show the location of the Npl• and Npld materials between 30 ø and-30 ø latitude investigated in this study. Base maps are the 1:15,000,000 Shaded Relief Map of Mars, Eastern and Western Regions [U.S. Geological Survey, 1985]. MORPHOLOGY OF HIG• IMPACT CRATERS A number of investigations have dealt with the general degrade d appearance of craters in the Martian highlands. Based on Mariner spacecraft data, McGill and Wise [1972] and Arvidson [1974] indicated that fresh, bowl-shaped craters grade into flatfloored, rimless craters. Using high-resolution Viking orbiter data, Grant and Schultz [1991a, b] compared styles of crater degradation in southern Ismenius Lacus to the evolution of terrestrial impact craters. These studies are important for determining how highland impact craters became degraded and for identifying the processes that operated to modify them. However, the Mariner-based studies presented broad crater classes without distinguishing smaller, significant features that are visible in Viking orbiter images. Also, highland studies north of 30 ø latitude are biased towards identifying the degradational process as aeolian in nature due to the presence of large airfall (i.e., dust) deposits in the region [Christensen, 1982, 1986; Greeley and Guest, 1987; Schultz and Lutz, 1988; Grizzaffi and Schultz, 1989; Dimitriou, 1990a, b; Grant and Schultz, 1990; Moore, 1990] which were emplaced subsequent to highland degradation and crater modification [Dimitriou, 199Os, b]. Highland crater populations in the equatorial region of Mars show styles of degradation that are consistent with fluvial processes. Fresh impact craters typically have sharply defined raised rims, hummocky floors, and obvious ejecta deposits (Figure 2a). Martian gravity causes some small-scale collapse of the rim to occur on craters with diameters greater than ~5 km, producing a fresh impact crater with a complex morphology [Pike and Davis, 1984; Pike, 1988]. The ejects associated with fresh Martian impact craters either radiates out from the center of impact (similar to most hmar craters), is lobate from the center and is said to be "fluidized" [Mouginis-Mark, 1979], or falls somewhere in between these two types. Fluidized ejects may represent the presence of subsurface volatiles [Carr et al., 1977] or may be the result of atmospheric deceleration of ejected particles [Schultz and Gault, 1979]. Geographic variations in the occurrence of these types of fresh impactscraters have been the subject of numerous CRADDOCK AND MAXWELL: ANCIENT FLUVIAL PROCESSES ON MARS 3455
Journal of Geophysical Research, 2011
1] Outcrop exposures imaged by the Opportunity rover at Victoria Crater, a 750 m diameter crater in Meridiani Planum, are used to delineate sedimentary structures and further develop a dune-interdune depositional model for the region. The stratigraphy at Victoria Crater, observed during Opportunity's partial traverse of its rim, includes the best examples of meter-scale eolian cross bedding observed on Mars to date. The Cape St. Mary promontory, located at the southern end of the rim traverse, is characterized by meter-scale sets of trough cross bedding, suggesting northward migrating sinuous-crested bed forms. Cape St. Vincent, which is located at the opposite end of the traverse, shows tabular-planar stratification indicative of climbing bed forms with meter-to decameterscale dune heights migrating southward. Promontories located between Cape St. Mary and Cape St. Vincent contain superposed stratigraphic units with northward and southward dipping beds separated by outcrop-scale bounding surfaces. These bounding surfaces are interpreted to be either reactivation and/or superposition surfaces in a complex erg sea. Any depositional model used to explain the bedding must conform to reversing northward and southward paleomigration directions and include multiple scales of bed forms. In addition to stratified outcrop, a bright diagenetic band is observed to overprint bedding and to lie on an equipotential parallel to the preimpact surface. Meter-scale cross bedding at Victoria Crater is similar to terrestrial eolian deposits and is interpreted as a dry dune field, comparable to Jurassic age eolian deposits in the western United States.
Dune formation on the present Mars
Physical Review E, 2007
We apply a model for sand dunes to calculate formation of dunes on Mars under the present Martian atmospheric conditions. We find that different dune shapes as those imaged by Mars Global Surveyor could have been formed by the action of sand-moving winds occuring on today's Mars. Our calculations show, however, that Martian dunes could be only formed due to the higher efficiency of Martian winds in carrying grains into saltation. The model equations are solved to study saltation transport under different atmospheric conditions valid for Mars. We obtain an estimate for the wind speed and migration velocity of barchan dunes at different places on Mars. From comparison with the shape of bimodal sand dunes, we find an estimate for the timescale of the changes in Martian wind regimes.
Journal of Geophysical Research, 2004
The evolution of the Martian crustal dichotomy boundary, which separates the southern cratered highlands from the northern lowland plains by 1-3 km of elevation, remains among the fundamental outstanding issues in Mars research. For a study area at Aeolis Mensae we show that fretted terrain formed exclusively in a >2 km thick, late Noachian ($3.7 Ga) sedimentary deposit that overlies the base of an older, cratered dichotomy boundary slope. In this equatorial study area, fretted terrain does not exhibit the debris aprons or lineated valley fills that are attributed to ground ice in otherwise similar, midlatitude fretted terrain in Arabia Terra. The massive deposit of fine sand or loess was probably transported from the north by wind and trapped against the precursor dichotomy slope, producing a similar initial form to the younger Medusae Fossae layered materials that occur east of Aeolis Mensae. Contemporary with the latest Noachian to early Hesperian decline in fluvial erosion, the fretting process likely initiated as the massive layer's indurated surface was compromised by fracture, cratering, or collapse into possible voids. In these depressions, grain impact or contact with water disaggregated the fine sedimentary materials, which were then largely deflated by wind. The fretting process largely ended when liquid water was no longer widely available for weathering during the early Hesperian period, although some degradation of the region by aeolian and slope processes has continued to the present.