Earth Impact Effects Program

Robert Marcus, H. Jay Melosh, and Gareth Collins

Welcome to the Earth Impact Effects Program: an easy-to-use, interactive web site for estimating the regional environmental consequences of an impact on Earth. This program will estimate the ejecta distribution, ground shaking, atmospheric blast wave, and thermal effects of an impact as well as the size of the crater produced.

Please enter values in the boxes below to describe your impact event of choice and your distance away. Then click "Calculate Effects" to learn about the environmental consequences.

Please re-enter the following items:
Projectile Density
Impact Velocity
Impact Angle
Target Density

Distance from Impact

Distance from Impact (in km)

Enter Impact Parameters

Projectile Parameters

Projectile Diameter (in meters)

Projectile Density (in kg/m3) or

Impact Parameters

Impact Velocity (in km/s)

This is the velocity of the projectile before it enters the atmosphere. The minimum impact velocity on Earth is 11 km/s. Typical impact velocities are 17 km/s for asteroids and 51 km/s for comets. The maximum Earth impact velocity for objects orbiting the sun is 72 km/s.

Impact Angle (in degrees)

The impact angle is measured from a plane tangent to the impact surface. This angle is 90 degrees for a vertical impact. The most probable angle of impact is 45 degrees.

Target Parameters

Target Density (in kg/m3) or




Tell me more...

Click here for a pdf document that details the observations, assumptions, and equations upon which this program is based. It describes our approach to quantifying the important impact processes that might affect the people, buildings, and landscape in the vicinity of an impact event and discusses the uncertainty in our predictions. The processes included are: atmospheric entry, impact crater formation, fireball expansion and thermal radiation, ejecta deposition, seismic shaking, and the propagation of the atmospheric blast wave.

Recent improvements in the airblast calculation are described here.





Earth Impact Effects Program Copyright 2004, Robert Marcus, H.J. Melosh, and G.S. Collins
These results come with ABSOLUTELY NO WARRANTY