Simulating the Chicxulub Asteroid Impact

A few seconds after the 10-kilometer-diameter asteroid strikes Earth, billions of tons of very hot debris are lofted into the atmosphere. Much of the debris is directed downrange (to the right and back of the image), carrying the horizontal momentum of the asteroid in this 45-degree impact. The asteroid plunges into 300 meters of water that overlies 3 kilometers of calcite, 30 kilometers of granite, and mantle materialÑlayers that correspond to those of the Chicxulub impact site in the late Cretaceous Period. At that time, the Yucatan Peninsula was on the continental shelf, which consisted mainly of fossilized coral reefs. This image is a perspective rendering of a density isosurface colored by the temperature of materials (0.5 eV = 10,000¡F). The scale is set by the back boundary, which is 256 kilometers long; the height of the debrisÕ Òrooster tailÓ is 50 kilometers.

Less than a minute after impact, the rooster tail has moved far downrange, out of the simulation. The dissipation of the asteroidÕs kinetic energy produces a stupendous explosion that melts, vaporizes, and ejects a substantial volume of calcite, granite, and water. The dominant feature here is the conical ÒcurtainÓ of hot debris that has been ejected and is now falling back to Earth. The turbulent material inside this curtain is still being accelerated by the explosion from the craterÕs excavation.

Two minutes after impact, the debris curtain has separated from the rim of the still-forming crater as debris in the curtain falls to Earth. The debris is deposited asymmetrically around the crater, with more falling downrange than uprange. The distribution of material in the ejecta can be used to determine the direction and angle of impact of the asteroid. Cores that have been obtained around the Chicxulub impact site are consistent with a southerly direction for the impact. Future drillingÑguided by simulations such as theseÑmay help to determine more definitively the geometry of impact.

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