Introduction: The observed morphologies of impact basins can only be explained by invoking dramatic weakening of the crater walls and floor during crater collapse, but the mechanism underlying the drop in strength is unknown. Here, we explore the possibility that strain-weakening along faults is the primary mechanism. We present a model of temperatureand pressure-dependant strain-weakening alon...

Dynamic compaction is a soil improvement method which has been widely used for the increase of bearing capacity through stress wave propagation during heavy tamping. The cost and time of project implementation can be effectively curtailed by developing a model that can be used in the design of dynamic compaction operations. The numerical models offered so far are mostly one or two-dimensional, ...

Introduction: Martian paleolakes have been offered as landing sites for in situ and sample-return missions because of their high probability of containing climatic and hydrologic records and potential biomarkers. Prospective paleolake sites are identified in closed craters primarily based on discrepancies between the craters' expected and measured depths and interpretation of associated fluvial...

ALH84001 is the only martian meteorite currently known with a crystallization age of 4.5 Ga. This ancient age indicates the meteorite must come from the ancient crust of Mars, located primarily in the southern hemisphere of the planet. The 4.56 Ga crystallization age, the 16 Ma ejection, and theoretical models of how material is ejected off Mars were used to identify possible source craters for...

Concentric crater fill (CCF) occurs in the interior of impact craters in midto high latitudes on Mars and is interpreted to have formed by glacial ice flow and debris covering. We use the characteristics and orientation of deposits comprising CCF, the thickness of pedestal deposits in midto high-latitude pedestal craters (Pd), the volumes of the current polar caps, and information about regiona...

Introduction: Impact craters are a dominant geological landform on Mars, the most Earth-like planet in the Solar System. The martian impact cratering record is more diverse than for Earth and the other terrestrial planets [e.g., 1]. Of particular interest is the presence of multiple layers of lobate or fluidized proximal ejecta deposits surrounding martian impact craters. These are collectively...

The origin of plains on Mercury, whether by volcanic flooding or impact ejecta ponding, has been controversial since the Mariner 10 flybys (1974-75). High-resolution images (down to 150 meters per pixel) obtained during the first MESSENGER flyby show evidence for volcanic vents around the Caloris basin inner margin and demonstrate that plains were emplaced sequentially inside and adjacent to nu...