A COMPUTATIONAL MODEL OF THE CHESAPEAKE BAY IMPACT

A numerical simulation of the Chesapeake Bay impact was performed using the CTH shock-physics hydrocode developed by Sandia National Laboratories. CTH is a multimaterial Eulerian hydrocode that explicitly solves conservation of mass, momentum and energy using equations-of-state capable of representing all phases of matter. It is used predominantly for solving high strain-rate problems and is widely used by the planetary impact community to help understand the cratering process on bodies throughout the solar system.

The Chesapeake Bay impactor was modeled as a 3.3 km diameter spherical asteroid consisting of dunite (density 3.32 g/cc). To simplify the calculation, two-dimensional axisymmetry was used. The projectile was assumed to be travelling vertically downward at 20 km/s. The target consisted of a 300 m layer of water overlying 200 m of water-saturated tuff and a "bedrock" of granite. The Earth's atmosphere was included to an altitude of 120 km.

The calculation was run forward in time to approximately 290 seconds after impact. Maximum depth of the transient cavity (approximately 15 km) occurred at about 30 seconds. Maximum radius of the transient cavity (approximately 43 km) occured by 120 seconds. Rebound of the central cavity lead to a region of central uplift approximately 10-15 km in radius. Removal of the surface water layer by air blast and re-impact of ejected materials occured to a radius of aproximately 67 km.

Material ejected from the crater was ballistically extrapolated for 6000 seconds after impact by which time all material had re-impacted the Earth's surface. Ejecta thicknesses at 150 km, 300 km and 600 km radii were 1 m, 1 cm and 1 mm respectively.

*Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.