Characterizing the Stratigraphy of the Nili Planum Region Outside Jezero Crater: Implications for Mars 2020 Strategic Planning (original) (raw)
Related papers
Sequence stratigraphy in extraterrestrial settings: The Jezero crater, Mars
Marine and Petroleum Geology, 2023
The analysis of high-resolution images provided by the Perseverance rover indicates the presence of a Gilbert type deltaic complex in the western part of the Jezero crater, which includes fluvial topsets, as well as subaqueous clinoforms. While previously considered to be genetically related, the topsets and the foresets are separated by subaerial unconformities and belong to different sedimentation cycles (depositional sequences) and systems tracts. Based on the stratal stacking patterns observed at Kodiak butte, the clinoforms belong to fallingstage systems tracts, as indicated by the downstepping trajectory of the clinoform rollovers, the occasional preservation of offlap, and the sharp-based nature of the clinoforms. In contrast, the topsets are part of the lowstand systems tracts of the overlying depositional sequences, and are separated from the underlying foresets by truncation surfaces (i.e., subaerial unconformities). The possible environments for the deposition of clinoforms in the Jezero crater range from lacustrine to marine. In the latter case, a connection between the Jezero Basin and a northern ocean can be inferred, allowing for the possibility of tidal processes influencing the patterns of deposition within the deltaic complex. This may explain the rhythmites observed in the deltaic foresets, although other explanations for the cyclic changes in lithology and energy conditions, such as seasonal variations in fluvial discharge and sediment load, are also possible. The location of the Jezero crater in the shoreline area of the Isidis Basin, which is a bay of the northern ocean, may have created a configuration of interconnected embayments able to amplify the otherwise small tidal range expected from the two moons of the planet. Clarification of the paleogeography at the time of deltaic progradation (c. 3.6-3.8 Ga) has major implications for the strategy of exploration for early life forms on Mars. The acquisition of rock samples from the Jezero Basin and the northern ocean are essential to gain further insight into the early land-ocean interaction and possible co-evolution of life and environments on Mars.
Journal of Geophysical Research: Planets
We report the results of geological studies by the Opportunity Mars rover on the Endeavour Crater rim. Four major units occur in the region (oldest to youngest): the Matijevic, Shoemaker, Grasberg, and Burns formations. The Matijevic formation, consisting of fine-grained clastic sediments, is the only pre-Endeavour-impact unit and might be part of the Noachian etched units of Meridiani Planum. The Shoemaker formation is a heterogeneous polymict impact breccia; its lowermost member incorporates material eroded from the underlying Matijevic formation. The Shoemaker formation is a close analog to the Bunte Breccia of the Ries Crater, although the average clast sizes are substantially larger in the latter. The Grasberg formation is a thin, fine-grained, homogeneous sediment unconformably overlying the Shoemaker formation and likely formed as an airfall deposit of unknown areal extent. The Burns formation sandstone overlies the Grasberg, but compositions of the two units are distinct; there is no evidence that the Grasberg formation is a fine-grained subfacies of the Burns formation. The rocks along the Endeavour Crater rim were affected by at least four episodes of alteration in the Noachian and Early Hesperian: (i) vein formation and alteration of preimpact Matijevic formation rocks, (ii) low-water/rock alteration along the disconformity between the Matijevic and Shoemaker formations, (iii) alteration of the Shoemaker formation along fracture zones, and (iv) differential mobilization of Fe and Mn, and CaSO 4 -vein formation in the Grasberg and Shoemaker formations. Episodes (ii) and (iii) possibly occurred together, but (i) and (iv) are distinct from either of these.
Journal of Geophysical Research: Planets, 2021
We have used Mars Exploration Rover Opportunity data to investigate the origin and alteration of lithic types along the western rim of Noachian-aged Endeavour crater on Meridiani Planum. Two geologic units are identified along the rim: the Shoemaker and Matijevic formations. The Shoemaker formation consists of two types of polymict impact breccia: clast-rich with coarser clasts in upper units; clast-poor with smaller clasts in lower units. Comparisons with terrestrial craters show that the lower units represent more distal ejecta from at least two earlier impacts, and the upper units are proximal ejecta from Endeavour crater. Both are mixtures of target rocks of basaltic composition with subtle compositional variations caused by differences in post-impact alteration. The Matijevic formation and lower Shoemaker units represent pre-Endeavour geology, which we equate with the regional Noachian subdued cratered unit. An alteration style unique to these rocks is formation of smectite and Si-and Al-rich vein-like structures crosscutting outcrops. Post-Endeavour alteration is dominated by sulfate formation. Rim-crossing fracture zones include regions of alteration that produced Mg-sulfates as a dominant phase, plausibly closely associated in time with the Endeavour impact. Calcium-sulfate vein formation occurred over extended time, including before the Endeavour impact and after the Endeavour rim had been substantially degraded, likely after deposition of the Burns formation that surrounds and embays the rim. Differences in Mg, Ca and Cl concentrations on rock surfaces and interiors indicate that mobilization of salts by transient water has occurred recently and may be ongoing. Plain Language Summary Data returned by the Mars Exploration Rover Opportunity was used to investigate rock origins along the western rim of Endeavour crater on Meridiani Planum, Mars. The Shoemaker formation consists of impact-formed breccia of two types: coarser-grained upper subunits and finer-grained lower subunits. The lower units represent ejecta from at least two older, more distant craters, while the upper units are ejecta from Endeavour crater. Subtle compositional differences are caused by differences in post-impact alteration along the crater rim. The lower Shoemaker units represent part of the pre-Endeavour rock sequence. An alteration style unique to these rocks is formation of Si-and Al-rich structures crosscutting bedrock. Post-Endeavour alteration is dominated by sulfate formation. Fracture zones in the rim include regions of alteration that produced Mg-sulfates as a dominant phase, plausibly closely associated in time with the Endeavour impact. Calcium-sulfate vein formation occurred over extended time, some before the Endeavour impact and some much later, likely after deposition of the sulfate-rich sandstones of Meridiani Planum. Differences in composition of rock surfaces and interiors indicate that mobilization of salts by transient water has occurred recently and may be ongoing on Mars.
Geomorphology of Ma'adim Vallis, Mars, and associated paleolake basins
Journal of Geophysical Research, 2004
1] Ma'adim Vallis, one of the largest valleys in the Martian highlands, appears to have originated by catastrophic overflow of a large paleolake located south of the valley heads. Ma'adim Vallis debouched to Gusev crater, 900 km to the north, the landing site for the Spirit Mars Exploration Rover. Support for the paleolake overflow hypothesis comes from the following characteristics: (1) With a channel width of 3 km at its head, Ma'adim Vallis originates at two (eastern and western) gaps incised into the divide of the $1.1 M km 2 enclosed Eridania head basin, which suggests a lake as the water source.
Icarus, 2021
Impact craters on Mars preserve diverse records of volcanic, fluvial, and glacial activities. Enigmatically, the preservation of these major activities or records altogether within impact craters is rare. We report one such new observation of impact craters that formed on a volcanic dome studied using data from the Mars Reconnaissance Orbiter's (MRO) Context Camera (CTX), High-Resolution Imaging Science Experiment (HiRISE), and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), Mars Global Surveyor's Mars Orbiter Laser Altimeter (MOLA), and Mars Express' High-Resolution Stereo Camera (HRSC). A ~20 km diameter impact crater, informally named as Degana-A, is formed within the ~50 km diameter impact crater Degana. Mineralogical analysis reveals exposures of low-calcium pyroxene and olivine deposits, which occupy Degana-A's eastern walls, leading to the idea that pristine Noachian bedrocks might be exposed from beneath the volcanic dome. Degana-A floor is completely covered by alluvial fans from all sides with distributaries. Within Degana crater, multiple fans are observed along its eastern to southern side only. The most likely source of water was the accumulation of snow on Degana crater walls, which possibly melted as a result of the impact of Degana-A. We observed a ~1 km wide breach on the eastern wall of Degana-A and the estimated maximum flow velocity is ~2 m/s and a runoff ~2.25 mm/hr. Over the south-facing walls, multiple moraine-like ridges superposed the fans, which suggests overprinting by glacial activities. The presence of fans and superposed moraine-like ridges located at the mid-latitudes (~23°S) implies atmosphere-derived snow/ice precipitation was possible. Chronologically, the dome is of Noachian age, whereas Degana crater formed in the Hesperian period and crater retention on the fans indicates late Hesperian to Amazonian ages. Overall, the preserved Noachian crustal material underneath a volcanic dome is rarely exposed in its pristine context, which offers a rare window into early igneous processes. This intriguing location also witnessed a climatic transition as implied by water/ice derived landforms formed by non-coeval events. 100 glacial landforms. Likewise, no mineralogical analysis has been carried out over this volcanic 101 dome to decipher the Noachian mineralogy. Thus, this region offers a unique chance to observe 102 volcanic, impact, glacial, and fluvial landforms in the same location, assessing whether the 103 processes that formed them occurred in concert or not. In addition, the composition of such 104 Noachian volcanoes is critical to understand the evolution of ancient volcanic crust on Mars (Xiao
Post-Viking View of Martian Geologic Evolution
1980
The mean density, 3.933 g/cm 3, and the estimated moment of inertia factor, 0.365, constrain the density distribution within Mars but do not define it uniquely. For plausible core densities, core radii can range from-•1350 to-•2200 km, with the core constituting from-•13 to-•35% of the planet's mass. Possible extremes for the zero-pressure density of the Martian mantle could be as high as-•3.6 g/cm 3 or as low as-•3.3 g/cm 3. The Martian mantle is probably denser than the terrestrial mantle; however, the actual density and composition of the Martian mantle are not well constrained by present data. The dominant Martian lavas are probably marie or ultramarie. Viking lander analyses suggest that soils are hydrated, Fe 3+bearing weathering products of marie rocks. Earth-based reflectance spectra indicate olivine (or basaltic glass) and pyroxene in dark areas and several percent Fe 3+ oxides in bright areas; integral disk spectra indicate the presence of H20 ice and mineral hydrates. Stable weathering products under current surface conditions are primarily oxides and carbonates. Martian surface materials probably consist of variable proportions of made igneous minerals and weathering products; the actual mineralogy is not well constrained by present data. A major geologic dichotomy exists between the complex northern plains and the ancient southern cratered terrain. The Thatsis plateau, which dominates the low-degree harmonics of the gravity field, appears to be only partially compensated; Olympus Mons appears to be completely uncompensated. Substantial stresses must be supported, either statically by a thick, rigid lithosphere, or dynamically. Mean crustal thicknesses ranging from 23 to 40 km have been obtained from modeling of Bouguer gravity data. Lithospheric thicknesses ranging from 25 to 50 km under volcanoes in the Thatsis and Elysium provinces to > 150 km under Olympus Mons have been obtained from consideration of the effects of mass loading by volcanic constructs. Many of the compressional and extensional features on Mars have orientations consistent with formation by fracturing in response to loading by the Thatsis plateau. The deficiency of small craters within cratered terrain is attributed to obliteration by volcanism which formed the intercrater plains in cratered terrain. These intercrater plains, which appear to be the first units formed after the ancient cratered terrain, overlap in relative ages with the ridged plains and the fretted regions; remaining plains units are younger. The maximum resurfacing rate due to volcanism occurred between 1.0 and 1.5 b.y. ago if a constant cratering flux is assumed and between 3.5 and 4.0 b.y. ago if the lunar cratering flux (scaled to Mars) is assumed. Thermal evolution models have considered the formation of initial crust, core formation, mantle differentiation, and planetary radius changes, but not the major geologic asymmetries of Mars. The time scales of thermal evolution models can be lengthened or shortened by making various assumptions about initial temperatures and heat sources. Models in which the core formed in the first billion years and in which the peaks of mantle differentiation, volcanism, and planetary radius occur between 1.5 and 3.5 b.y. ago are consistent with a Martian cratering flux intermediate between the constant flux model and the scaled lunar flux. The high •SN/•nN ratio of the Martian atmosphere, 1.7 times the terrestrial value, is ascribed to mass-dependent loss of 10-150 times the present amount of atmospheric •nN. The absence of observable isotopic effects in C and O suggests that atmospheric CO2 and H20 must exchange periodically with a larger, normally nonatmospheric reservoir. The Martian atmosphere exhibits a 'planetary' type pattern of noble gas abundances, with xenon depleted in relation to the other noble gases. Estimates of the whole planet column abundances of CO2 and H20 range from 290 to 8000 g/cm 2 and from 600 to 1600 g/cm 2, respectively. Amounts of H20 and CO2 which are comparable to or perhaps greatly in excess of the whole planet estimates made on the basis of atmospheric noble gas abundances can be stored in plausible reservoirs: the residual polar caps; hydration, oxidation, and carbonation of surface materials; adsorption and absorption into the regolith; and as subsurface ices. A number of surface features have morphologies which appear to require tens of meters of water, and perhaps more, for their formation: fretted terrain, channels, patterned or polygonal ground, rampart ejecta deposits, and possible table mountains.
Martian Cratering 7: The Role of Impact Gardening
Icarus, 2001
Viking-era researchers concluded that impact craters of diameter D < 50 m were absent on Mars, and thus impact gardening was considered negligible in establishing decameter-scale surface properties. This paper documents martian crater populations down to diameter D ∼ 11 m and probably less on Mars, requiring a certain degree of impact gardening. Applying lunar data, we calculate cumulative gardening depth as a function of total cratering. Stratigraphic units exposed since Noachian times would have experienced tens to hundreds of meters of gardening. Early Amazonian/late Hesperian sites, such as the first three landing sites, experienced cumulative gardening on the order of 3-14 m, a conclusion that may conflict with some landing site interpretations. Martian surfaces with less than a percent or so of lunar mare crater densities have negligible impact gardening because of a probable cutoff of hypervelocity impact cratering below D ∼ 1 m, due to Mars' atmosphere. Unlike lunar regolith, martian regolith has been affected, and fines removed, by many processes. Deflation may have been a factor in leaving widespread boulder fields and associated dune fields, observed by the first three landers. Ancient regolith provided a porous medium for water storage, subsurface transport, and massive permafrost formation. Older regolith was probably cemented by evaporites and permafrost, may contain interbedded sediments and lavas, and may have been brecciated by later impacts. Growing evidence suggests recent water mobility, and the existence of duricrust at Viking and Pathfinder sites demonstrates the cementing process. These results affect lander/rover searches for intact ancient deposits. The upper tens of meters of exposed Noachian units cannot survive today in a pristine state. Intact Noachian deposits might best be found in cliffside strata, or in recently exhumed regions. The hematite-rich areas found in Terra Meridiani by the Mars Global Surveyor are probably examples of the latter.
Analysis of crater valleys, Noachis Terra, Mars: Evidence of fluvial and glacial processes
The precise mechanism for the formation and evolution of crater valley networks in the Martian southern highlands remains under debate, with precipitation, groundwater flow, and melting induced by impact being suggested. We studied valley networks within four craters of the Noachis Terra highlands that were representative of similar features in Noachis Terra and where orbital data existed for analysis in order to characterise their morphology and infer possible processes involved in their formation and evolution. We found evidence for valleys carved by liquid water and ice-related processes. This included strong evidence of liquid water-based valley formation through melting of ice-rich deposits throughout our study area, suggesting an alternative to previously suggested rainfall or groundwater-based scenarios. The location of these valleys on steeply sloping crater walls, as opposed to the shallow slopes of the highlands where Martian valleys are typically found, suggested that our 'fluvial' valleys had not evolved a more structured fluvial morphology as valley networks found on the Martian plains. Our studied valleys' association with ice-rich material and abundant evidence for erosion caused by downslope flow of ice-rich material are consistent with a cold, wet Mars hypothesis where accumulation, flow, and melting of ice have been dominant factors in eroding crater valleys. Additionally, analysis of valley morphology with slope and aspect suggested a greater dependence on local geology and presence of volatiles than larger valley networks, though ice-related valleys were consistently wider for their length than valleys assessed as fluvial carved. We assessed that local conditions such as climate, geology, and availability of ice-rich material played a major role in the erosion of crater valleys at our study site.
Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars
Science
The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide–rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.