The simulation starts with the comet 30 kilometers above the surface. The comet produces a strong luminescent bow shock in the atmosphere as it speeds downwards. Seven-tenths of a second later it hits the ocean with an impact energy of 300 gigatons of TNT - about 10 times the explosive power of all the nuclear weapons in existence in the 1960s at the height of the Cold War - forming a large transient cavity in the ocean and a dent in the ocean floor. The comet itself is almost instantaneously vaporized, along with 300 to 500 cubic kilometers of ocean. This high-pressure steam explosion rises into the atmosphere. Comet vapor and water vapor are ejected into ballistic trajectories that will take it around the globe, with some of it even achieving escape velocity.
Video of comet impact (2.5MB AVI file for PCs)
Video of comet impact (1.7MB MOV file for Macs)