3D Analysis of fracture networks and fine-scale sedimentary structures for reconstructing ancient Martian habitable environments

"Our experience of studying life on Earth tells us that liquid water is a major ingredient for habitability and life. Evidence for hydrological activity comes from sedimentary rocks which formed in aqueous environments such as delta plains and lake beds, and also from fractures with mineral fills, now outcropping on the surface, which likely formed in the sub-surface due to groundwater flow.
This proposal aims to prepare for the ExoMars 2020 rover mission by characterising terrestrial analogs of fracture systems and sedimentary structures used to interpret the depositional setting of sedimentary rocks. The ExoMars 2020 Rover will be equipped with a stereo Panoramic Camera (PanCam) system. The PanCam is the 'eyes' for the rover science team, and the images will be key data for informing instrument teams of the best locations for drilling up to 2 m into the surface of the planet. An advantage of the stereo-configuration of the PanCam is that images can be converted into 3D digital outcrop models (DOMs), enabling us to collect quantitative measurements of features from the processed images.
Fractures in rocks occur when they are placed under stress, and most commonly where circulating fluids are present. Fracture analysis involves determining the relative direction in which the fracture walls move, to infer the directions of the stresses which caused them, as well as measuring the orientation of the fracture in three dimensions, determining their relative ages, and measuring their dimensions. NASA's Mars Science Laboratory mission has encountered pervasive fracturing in all the stratigraphic units it has encountered along its traverse. Many of these show mineral infills, and changes in the cement in the rocks surrounding the fracture walls; all features considered to be a result of fluids travelling through the fractures.
Sedimentary structures are features in sedimentary rocks that are formed during transport and deposition of sediment. They provide crucial evidence used for reconstructing an ancient environment. Similar structures to those found in lakes, riverbeds and desert dunes have been discovered by previous missions, and used to developed detailed pictures of what the conditions were like when those rocks were deposited, and how those conditions changed. We want to understand the influence of camera resolution on rover approach - at what distance do we need to be from a sedimentary feature to be able to see it, and if necessary drive towards it? What features can be seen at distances where the resolution is too low to directly identify these structures and used to infer their possible presence? At what distances can we be sure that the features we are seeing are reliable?
Comparable features can be found on Earth, and we propose to use the Aberystwyth University PanCam Emulator (AUPE) to image relevant outcrops, providing us with panoramas and 3D DOMs representative of those collected with the PanCam. We will analyse these datasets in the Planetary Robotics 3D Viewer (PRo3D) and develop specific fracture analysis toolkits to unravel the information provided by these complex geological features. Field analysis of the same outcrops will help us to fully understand what effects the resolution of the cameras has on interpretation and analysis. The key questions we will be answering with this project are: What formational processes caused the fractures, for example, hydraulic fracturing, rapid sediment loading, unloading due to erosion, bolide impact, desiccation at a palaeosurface? What was the relative timing of different fracture events? and what was the distribution and orientation of the stress field?
The proposed work will allow for further development of image processing and analysis capabilities for the PanCam instrument enabling the science team to get a high return from data collected by the ExoMars mission, as well as help us to understand the behaviour and timing of ground and surface water on Mars."