Numerical modelling of large scale asteroid impact events: Crater formation on continental and oceanic targets, environmental pertubations and code development

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Asteroid collisions with the Earth have occurred throughout the entire history of our planet andbrought catastrophe to the regional geology and global environment. The importance of pastimpacts on the evolution of Earth and life as it exists today and the threat of future such eventsmake the reconstruction of the cratering process a crucial endeavour. In the first phase of theproject meteorite impact on marine targets and the generation and propagation of tsunami-likewaves were analysed by numerical modelling to evaluate the consequences of such events.Concurrently, a new 3D hydrocode to simulate impact processes was developed based on theexisting 2D version. 3D modelling is mandatory to investigate the effect of the angle of impact,and target heterogeneities (inclined layers of divers material properties) on the craterformation process. Despite the overall circular shape of impact structures it is a matter of factthat meteorite impact happens to be oblique. Preliminary results of a parameter study of craterefficiency as a function of impact angle yielded new promising results that will lead to refinedscaling laws for the important relation between the kinetic impact energy and resulting cratersize. Much progress was achieved in modelling the damage in rocks underneath craterstructure due to the shock wave loading and shear deformation during an impact event.Currently, only a qualitative description of the fragmentation state is possible (size and extent of fragmentation zone); however, for a direct comparison with geophysical anomalies atimpact structures a quantification of the increase in pore space due to shear bulking(dilatancy) is planed. For this reason a porosity-model was developed and implemented in thecode. So far, the compaction of pore space can be calculated and the development of a modelto determine the production of open pore space by shearing and straining is planed.Resolving these two issues, the effect of impact angle and target heterogeneities, and aquantitative description of subsurface target modifications will greatly improve ourunderstanding of impact cratering and will help to estimate size and, thus, the consequencesof impact events in past and future.