The Origin of the Fracture Networks in the Mudstones of Gale Crater Mars; Their Implications Regarding the State of Stress and Fluid Pressure During Their Formation and the Depth to Which They Were Buried

The aim of this article is to establish what can be determined about conditions on Mars during the formation of the fractures and veins that characterize the mudstones which crops out in Gale crater, and to determine whether these rocks represent superficial, alluvial deposits which have remained close to the surface or whether they have been subjected to significant burial and compaction. Spectacular, close-up images of the fracture and vein networks on horizontal bedding planes reveal their geometries in great detail and this facilitates fracture analysis, a technique that can be used to determine the order in which the various fractures were formed and the stress field operating during their formation. The veins and their textures give an indication of the mechanism of formation of the fractures and of the possible role of high fluid pressures. In addition, the geometry of the veins when viewed in a vertical section can be used to indicate the amount of compaction that the mudstones have experienced which can be used to estimate the minimum depth of burial that has occurred.