This activity allows students to calculate the mass, size, and kinetic energy of an asteroid that struck Earth 66 million years ago, based on the total abundance of iridium in a sediment layer. It supports concepts presented in the short film The Day the Mesozoic Died.

The activity begins with students watching the film, which describes the discovery of a layer of clay at the boundary between the Cretaceous and Tertiary rock layers (the K-T boundary). Through chemical analysis, scientists discovered that the layer contained an extraordinary concentration of the element iridium, which is rare in Earth’s crust but common in asteroids and comets. After watching the film, students conduct a series of calculations to estimate the mass and size of the K-T asteroid, based on the total abundance of iridium in the K-T boundary layer. They then estimate the kinetic energy of the meteorite as it struck Earth and compare the amount to that of other high-energy events.