Impact: Earth!

A Web-based program for quickly estimating the regional environmental consequences of a comet or asteroid impact on Earth

The program requires six inputs: impactor diameter, impactor density, impact velocity before atmospheric entry, impact angle, the distance from the impact at which the environmental effects are to be calculated, and the target type (sedimentary rock, crystalline rock, or a water layer above rock).

The program includes novel algorithms for estimating the fate of the impactor during atmospheric traverse, the thermal radiation emitted by the impact-generated vapor plume (fireball), and the intensity of seismic shaking.

The program also approximates various dimensions of the impact crater and ejecta deposit, as well as estimating the severity of the air blast in both crater-forming and airburst impacts.

In the associated paper, we illustrate the utility of the application by examining the predicted environmental consequences across the United States of hypothetical impact scenarios occurring in Los Angeles. We find that the most wide-reaching environmental consequence is seismic shaking: both ejecta deposit thickness and air-blast pressure decay much more rapidly with distance than with seismic ground motion. Close to the impact site the most devastating effect is from thermal radiation; however, the curvature of the Earth implies that distant localities are shielded from direct thermal radiation because the fireball is below the horizon.