16 April 2004

Asteroid impact calculator

Many articles have appeared in recent years about the hypothetical damage that would be caused by the collision with Earth of asteroids of various sizes. The University of Arizona has developed an intriguing asteroid impact calculator that adds a new dimension to the asteroid impact threat. Developed by Robert Marcus, H. Jay Melosh and Gareth Collins, the Earth Impact Effects Program (www.lpl.arizona.edu/impacteffects/m) allows the user to quickly see the estimated atmospheric and terrestrial effects of an asteroid impact anywhere on Earth.

The Impact Effects Program is easy to use. For example, here are just some of the parameters and predicted effects given by the program should a 100-meter diameter iron object strike dry land 10 km (6.2 miles) from your present location:

Asteroid Parameters:

Distance from Impact: 10.00 km = 6.21 miles
Projectile Diameter: 100.00 m = 328.00 ft = 0.06 miles
Impact Velocity: 17.00 km/s = 10.56 miles/s
Impact Angle: 30 degrees
Energy: 1.45 x 102 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 5.1 x 10³ years

Crater Size:

Final Crater Diameter: 2.92 km = 1.82 miles

Thermal Radiation:

Visible fireball radius: 1.7 km = 1.0 miles
The fireball appears 38.3 times larger than the sun
Thermal Exposure: 2.87 x 105 Joules/m²
Duration of Irradiation: 2 seconds
Radiant flux (relative to the sun): 130.7

Seismic Effects:

The major seismic shaking will arrive at approximately 2.0 seconds.
Richter Scale Magnitude: 6.0

Air Blast:

The air blast will arrive at approximately 33.3 seconds.
Max wind velocity: 202.1 m/s = 452.1 mph
Sound Intensity: 10³ dB (May cause ear pain)

Damage Description:

Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Highway truss bridges will collapse.

Glass windows will shatter.

Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

The program provides much more information. So if you want to find out what will happen in any scenario you wish to envision, visit www.lpl.arizona.edu/impacteffects/m.

Forrest M. Mims III.