Modeling asteroid collisions and impact processes

As a complement to experimental and theoretical approaches, numerical modeling has become an important component to study asteroid collisions and impact processes. In the last decade, there have been significant advances in both computational resources and numerical methods. We discuss the present state-of-the-art numerical methods and material models used in "shock physics codes" to simulate impacts and collisions and give some examples of those codes. Finally, recent modeling studies are presented, focussing on the effects of various material properties and target structures on the outcome of a collision.Comment: Chapter to appear in the Space Science Series Book: Asteroids IV. Includes minor correction

Insurance and Meteors Fall: Proposal of a Methodology for Estimating the Risk and Modelling Consequences for the Insurance Sector in France

International audienceIn parallel to the action of States and international organizations, the insurance sector is one that contributes to the resilience of human societies against the occurrence of natural disasters such as weather events, seismic ones and other ones. The action principle of this sector is characterized by at least three mechanisms: prevention for concerned people, compensation and portfolios reinsurance. The risk of meteor fall is not valued appropriately by this sector yet. However, our planet receives meteors every day, some of which could cause significant damages on urban areas or economic ones (industrial, shopping centres, recreation places etc.). From the analysis of the data concerning the asteroids that have impacted the Earth and which have a likelihood to do so, we present here a methodology to estimate the damages resulting from the impact of objects of sizes up to the maximum threshold for regional damages (a few hundreds of meters) on some given territory. The French territory is chosen as an example because we can describe its area with the appropriate spatial databases (population density, building location etc.). This approach is based on an initial definition phase of collision scenarios. Then, a second phase consists in the accurate modelling of the territory taking into account the land-use, the spatial distribution of insurance company stakes, and the characterization of the biophysical vulnerability of the stakes using thresholds of dangerous phenomena (overpressures, thermal radiations etc.). The third phase is related to the impact simulation on the territory and the estimation of the stakes potentially exposed

Craters Without Ejecta

A significant portion of the Solar System's population of minor bodies may be quite porous. A unique aspect of crater formation in porous bodies is that large craters may form without the ejecta deposits that are associated with craters on less porous bodies. In this paper. laboratory experiments and scaling theories are used to identify the conditions under which ejecta deposits are suppressed. The results are consistent with the interpretation that large craters on asteroid Mathilde (porosity approx. 50%) and Saturn's moon Hyperion (porosity >40%) apparently formed without producing Significant ejecta deposits. while smaller bodies do have notable regoliths