New evidence for a volcanically, tectonically, and climatically active Mars (original) (raw)

The evolution of volcanism, tectonics, and volatiles on Mars-an overview of recent progress

Lunar and Planetary …, 1991

Among the principal accomplishments of the M E W project are several important and widely accepted scientific findings about Mars. The global and regional volcanic flux has been established from systematic geological mapping using V i g images, providing a relative volcanic chronology for most of martian history. Petrologic and chemical analyses of SNC meteorites, inferred to have been derived &om Mars, have revealed an abundance of volatile materials, including hydrous minerals (amphiboles), oxidized sulfur, possible carbonates, and various salts; these results provide direct evidence that Mars is likely to be ~olatile~rich. Geological mapping and temporal groupings of major fault systems have provided strong new c o n s b t s on the sequence and timing of martian tectonic events, particularly in the vicinity of the Tharsis region. Substantial progress was also forthcoming on several fundmental but incompletely resolved aspects of martian evolution during the MEVTV program. The origin of the crustal dichotomy on Man was the subject of intensive investigations, and two classes of hypotheses have emerged: One relates the northern lowlands to the effects of l q e impact(s); the other calls for tectonic foundering subsequent to subcrustal erosion by mantle convection. The kinematics and mode of formation of wrinkle ridges are the subjects of continuing research. While it is clear that these features represent compressional deformation, whether they are predomhantly the expression of buckling or faulting remains problematic, as do the cause and implications of their remarkably straight trends and periodic spacing in some locales. Isotopic and petrologic analyses have revealed significant variations within the group of SNC meteorites that, if these objects come from Mars, suggests heterogeneous sources for the parental martian magmas. Finally, several intriguing new ideas have resulted from project-sponsored research and workshop discussions. A number of tectonic features have been identi£ied as probable transcurrent faults documenting horizontal offsets of at least several tens of kilometers. Such faulting, along with the large extensional strains required to form Valles Marineris, could indicate an early episode of significant horizontal motions of lithospheric blocks. One speculative hypothesis is that such motions were accommodated in a very early episode of plate tectonics on Mars, during which the original lithosphere of the northern lowlands was subducted beneath the Tharsis region and new lithosphere with thinner crust was generated at a now-extinct spreading center. This hypothesis, which remains to be tested rigorously, links the formation of the crustal dichotomy to the formation of Tharsis. INTRODUrnON The organjzation of the MEVm project was styled after that Mars has been the target of a number of ambitious spacecraft of the successful MECA project. It combined elements of a missions, including the American Viking orbiters and landers project approach and targeted research by independent in the late 1970s and, more recently, the m e t Phobos investigators. Specific goals and objectives were defined from spacecraft in 1989. Soon after the Viking mission it became the project perspective, but investigators were funded clear that data from that mission would constitute a long-term individually and operated independently within the context of source of important information about the nature and the study. The first meeting of the M E W project was held evolution of Mars. In recognition of this potential, NASA in the spring of 1987, where a science steering committee was established the Mars Data Analysis Program (MDAP) in 1979 chosen and general guidelines for the project were defined. to coordinate the funding and the direction of Mars research. ~artici~ation-in M * was open to-all investigators with The first of several major thematic investigations supported by research interests encompassed by the goals of the project, MDAP was a focused three-year study project entitled "Mars: regardless of funding source, to ensure broad-based involve-Evolution of its Climate and Atmosphere" (MECA), initiated ment. A program of workshops was organized to provide in 1984 under the direction of the Lunar and Planetary cohesion to the project and to ensure that the project's Institute in Houston, Telras. The success of the MECA project objectives would be addressed (Table 1). The MEVTV project (CIiffwd et d., 1988a,b) led to a follow-on three-year study provided a rich environment for collaborative efforts between project entitled "Mars: Evolution of Volcanism, Tectonics, and investigators from very diverse fields of investigation, often Volatiles" (MEVTV), initiated by NASA in 1987, also under the resulting in new approaches to d8icult problems related to direction of the Lunar and Planetary Institute. the study of Mars.

Modern Mars' geomorphological activity, driven by wind, frost, and gravity

Geomorphology, 2021

Extensive evidence of landform-scale martian geomorphic changes has been acquired in the last decade, and the number and range of examples of surface activity have increased as more high-resolution imagery has been acquired. Within the present-day Mars climate, wind and frost/ice are the dominant drivers, resulting in large avalanches of material down icy, rocky, or sandy slopes; sediment transport leading to many scales of aeolian bedforms and erosion; pits of various forms and patterned ground; and substrate material carved out from under subliming ice slabs. Due to the ability to collect correlated observations of surface activity and new landforms with relevant environmental conditions with spacecraft on or around Mars, studies of martian geomorphologic activity are uniquely positioned to directly test surface-atmosphere interaction and landform formation/evolution models outside of Earth. In this paper, we outline currently observed and interpreted surface activity occurring within the modern Mars environment, and tie this activity to wind, seasonal surface CO2 frost/ice, sublimation of subsurface water ice, and/or gravity drivers. Open questions regarding these processes are outlined, and then measurements needed for answering these questions are identified. In the final sections, we discuss how many of these martian processes and landforms may provide useful analogs for conditions and processes active on other planetary surfaces, with an emphasis on those that stretch the bounds of terrestrial-based models or that lack terrestrial analogs. In these ways, modern Mars presents a natural and powerful comparative planetology base case for studies of Solar System surface processes, beyond or instead of Earth.

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.

Summary: New Views and New Directions in Mars Research

2001

The articles presented in this book reflect an interaction between geochemists, geophysicists, and photogeologists, who combined their expertise to focus on the chronology and evolution of Mars. A goal of our meeting was to offset some pressures that tend to isolate these groups from each other. As a result, we hoped to provide more integrated view, revealing Mars as a planet where we have access to primordial 4.5 Gyr-old crustal material, to diverse surfaces created during major geological processing before 3 Gyr ago, probably associated with a denser atmosphere and more fluvial environment, and also to exposures of volcanism, water release, weathering, gullying, and exhumation, all operating within the last few 100 Myr. Neither Earth nor Moon offers such a long-term, complete geologic record. This is a Mars with much longer-lived and varied geological activity than many had thought two decades ago (the time of the preparation of the major Mars conference volume, from the University of Arizona Press; Kieffer et al., 1992).

An overview of sedimentary volcanism on Mars

Extensive fields of sub-kilometre-to kilometre-scale mounds, cones, domes, shields, and flow-like edifices cover large parts of the martian lowlands. These features have been compared to structures on Earth produced by sedimentary volcanism -a process that involves subsurface sediment/fluid mobilisation and commonly releases methane to the atmosphere. It was proposed that such processes might help to explain the presence of methane in the martian atmosphere and may also have produced habitable, subsurface settings of potential astrobiological relevance. However, it remains unclear if sedimentary volcanism on Earth and Mars share genetic similarities and hence if methane or other gases were released on Mars during this process. The aim of this review is to summarise the current knowledge about mud-volcano-like structures on Mars, address the critical aspects of this process, identify key open questions, and point to areas where further research is needed to understand this phenomenon and its importance for the Red Planet's geological evolution. We show here that after several decades of exploration, the amount of evidence supporting martian sedimentary volcanism has increased significantly, but as the critical ground truth is still lacking, alternative explanations cannot be ruled out. We also highlight that the lower gravity and temperatures on Mars compared to Earth control the dynamics of clastic eruptions and surface emplacement mechanisms and the resulting morphologies of erupted material. This implies that shapes and triggering mechanisms of mud-volcano-like structures may be different from those observed on Earth. Therefore, comparative studies should be done with caution. To provide a better understanding of the significance of these abundant features on Mars, we argue for follow-up studies targeting putative sedimentary volcanic features identified on the planet's surface and, if possible, for in situ investigations by landed missions such as that by the Zhurong rover.

New Perspectives on Ancient Mars

Science, 2005

Mars was most active during its first billion years. The core, mantle, and crust formed within È50 million years of solar system formation. A magnetic dynamo in a convecting fluid core magnetized the crust, and the global field shielded a more massive early atmosphere against solar wind stripping. The Tharsis province became a focus for volcanism, deformation, and outgassing of water and carbon dioxide in quantities possibly sufficient to induce episodes of climate warming. Surficial and near-surface water contributed to regionally extensive erosion, sediment transport, and chemical alteration. Deep hydrothermal circulation accelerated crustal cooling, preserved variations in crustal thickness, and modified patterns of crustal magnetization.