Eileen Ryan Planetary Science Institute FY 96: $53,917 For 24 months. A Numerical Analysis of Collisions in the Solar System. A major process affecting the growth and evolution of planetary bodies is hypervelocity impact. Although some of the basic principles of impact phenomena are moderately well understood, how material fragments near the impact site and how initial conditions affect that fragmentation have been difficult to quantify. Also, the dependence of fragmentation outcome on target size is not well defined. Dr. Ryan and colleagues have developed and tested a two-dimensional Lagrangian hydrocode for modeling collisional fragmentation. Since gravitational effects are incorporated into the code, it is highly useful in the simulation of large-scale impact events beyond the reach of laboratory studies. The ability to characterize the outcome of an impact event of any size given a particular set of initial conditions is applicable to many problems: asteroid impacts on planetary surfaces, collisional evolution of the asteroid belt, asteroid family formation, planetesimal accretion, ring particle dynamics, and meteorite delivery mechanisms, for example. The goal of Dr. Ryan's present study is to improve the modeling of impact events by modifying the 2-dimensional code to include the effect of target porosity/internal fractures. The code will then be extended to 3 dimensions during the second funding year. The results of this modeling will be applied to better undertand collisions in the Solar System, primarily the problem of the formation of asteroid families. ====================================================
