Earth Impact Effects Program

Robert Marcus, H. Jay Melosh, and Gareth Collins

Please note: the results below are estimates based on current (limited) understanding of the impact process and come with large uncertainties; they should be used with caution, particularly in the case of peculiar input parameters. All values are given to three significant figures but this does not reflect the precision of the estimate. For more information about the uncertainty associated with our calculations and a full discussion of this program, please refer to this article

Your Inputs:

Distance from Impact: 10.00 km ( = 6.21 miles )
Projectile diameter: 12.00 meters ( = 39.40 feet )
Projectile Density: 2000 kg/m3
Impact Velocity: 20.00 km per second ( = 12.40 miles per second )
Impact Angle: 45 degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock


Energy before atmospheric entry: 3.62 x 1014 Joules = 0.86 x 10-1 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 16.7 years

Major Global Changes:

The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:

The projectile begins to breakup at an altitude of 68200 meters = 224000 ft
The projectile bursts into a cloud of fragments at an altitude of 32600 meters = 107000 ft
The residual velocity of the projectile fragments after the burst is 15.1 km/s = 9.4 miles/s
The energy of the airburst is 1.54 x 1014 Joules = 0.37 x 10-1 MegaTons.
No crater is formed, although large fragments may strike the surface.

Air Blast:

What does this mean?

The air blast will arrive approximately 1.72 minutes after impact.
Peak Overpressure: 541 - 1080 Pa = 0.00541 - 0.0108 bars = 0.0768 - 0.154 psi
Max wind velocity: 1.27 m/s = 2.84 mph
Sound Intensity: 55 dB (Loud as heavy traffic)

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.

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