Stress and Deformation on Mars, 20-9314Printer Friendly Version
Inclusive Dates: 05/06/02 - 05/06/04
Background - Mars is to be the subject of intensive investigation during the present and coming decades. Included in the planned missions are remote-sensing activities from orbit and lander/rover missions as precursors to future sample return missions. To date, there have been few process-level assessments of the relationships between deformation processes and the flow of surface and subsurface water, the structural association of surface and subsurface mineral deposits, and the influence of deformation processes on volcanism on Mars. On Earth, crustal deformation such as faulting, fracturing, and folding strongly influences surface topography, distribution and exposure of rock units, flow and accumulation of surface water, flow and entrapment of subsurface fluids (such as groundwater, oil, and natural gas), ore mineralization, climate conditions, heat flow in the crust, and seismicity. From "black smokers" and associated chemosynthetic communities in the deep ocean, to springs and associated oases in deserts, biological communities in relatively hostile environments on Earth are frequently associated with faults and fractures because of the presence and circulation of water along these structures. For a very wide range of purposes and processes, understanding deformation features at or near the Earth's surface has been instrumental in exploring for natural resources, and for understanding the evolution of the Earth's crust and its relationship with the hydrosphere, atmosphere, and mantle. Based on the many similarities between Earth and Mars, it is probable that deformation processes and in situ stress fields have a profound influence on fluid movement, related surface and subsurface mineralization, and the potential for past and current existence of life on Mars.
An important need in the characterization of Mars crustal processes is detailed analysis of structural features, stress field distribution and evolution, and approaches for analyzing the crustal stresses and influence on structures during and after their formation. Results of such investigations should be employed where mission planning includes such landing-site objectives as drilling, groundwater and mineral exploration, placement of seismic monitoring networks, or exploration for water-related mineral deposits that might harbor Martian fossils or even current life forms. The Institute has unique internally developed capabilities to perform these analyses and thus become recognized technical leaders in this area of Mars research.
Approach - The objective of this project was to use remotely sensed data from Mars to map structural features on the surface of Mars, and then to use advanced structural geology concepts and new technologies, including SwRI-developed 3DStress software, to characterize the causative stress fields in the Martian crust, and the resulting resolved stresses on faults and fractures that may influence ongoing deformation activity and subsurface fluid movement. In this project, our approach was to (i) acquire remotely sensed data, including MOLA and other relevant data, from NASA, processing data as necessary or appropriate in order to enhance structural features, and mapping structures exposed at the surface of Mars such as folds, faults, and extension-fracture networks; (ii) perform structural domain determination and stress field analysis, for which the primary tool was 3DStress, to determine assemblages of contemporaneous structures and the stress orientations responsible for deformation in different regions; (iii) use cross-cutting relationships (of structures with respect to each other and with respect to craters) with crater-counting based surface exposure age determinations to perform relative dating of structural assemblages and stress fields; (iv) evaluate likely deformation and stress field controls on subsurface fluid movement, mineralization, heat flow, and seismic activity on Mars; and (v) report work accomplished during the project, where possible in the form of manuscripts for peer-reviewed journals.
Accomplishments - During the course of this research, project staff developed considerable knowledge, skills and data bases for planetary image data preparation, manipulation and analyses. As a result of this effort, the following data sets are currently available through the Center for Nuclear Waste Regulatory Analyses: (i) Mars Orbiter Camera (MOC) visual images from the Mars Global Surveyor satellite, (ii) Mars Orbiter Laser Altimeter (MOLA) surface topography data, (iii) Viking orbiter image data from orbiter 1 and 2, available in variable spatial and spectral resolutions, and (iv) THEMIS, Thermal Emission Imaging System, data with image resolution in the visible spectrum of 19 meters per pixel. In addition, we procured the Integrated Software for Imagers and Spectrometers (ISIS) image processing software from the U.S. Geological Survey (USGS) that can incorporate multiple data forms (MOC, MOLA, THEMIS) for projection of image data on Mars. This software allows us to process the raw data for better image quality and to produce digital elevation models. In conjunction with ISIS, USGS has a website with tools for using ArcView for planetary data, PIGWAD. We have downloaded scripts and ArcView extensions from this website that allow us to create georeferenced world files for use in ArcView and to incorporate Mars coordinate systems and projections into ArcView. The project team has developed an organized and structured approach to existing planetary data. The combination of skilled and experienced personnel, an extensive and comprehensive collection of commercial and custom data processing techniques and software (both planetary and terrestrial) and state-of-the-art hardware systems, provides opportunities to contribute to a wide range of planetary geology and geophysical research.
A major focus of this research was the detailed characterization, interpretation, and modeling of pit crater chains. Our research produced a fundamental reinterpretation of the origin and importance of pit crater chains on Mars. Based on our analysis of Martian stress conditions, we interpret that a zone of dilational faulting is likely to be present on Mars similar to the upper 2 km of the Earth's crust, and may extend more than 2.5 times deeper on Mars than on Earth. As noted in our recent journal articles, pit chain development on Mars provides key information concerning the style of deformation, surface flow and subsurface fluid storage, stress fields, seismicity, and crustal materials on Mars. As emphasized in a recent article at SPACE.com (http://www.space.com/scienceastronomy/mars_quakes_041011.html), we also conclude that pit crater chains are some of the youngest landforms on Mars, and their pristine morphologies may be indicative of relatively recent or active faulting on Mars. Understanding this process of pit chain formation in response to active faulting can be used to guide future mission planning - specifically the design and implementation of a seismic monitoring program for Mars. Completion of the project led to an active Martian structural geology research program at Southwest Research Institute.