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: 30.00 km ( = 18.60 miles )

Projectile diameter: 1000.00 meters ( = 3280.00 feet )

Projectile Density: 100 kg/m³

Impact Velocity: 8.00 km per second ( = 4.97 miles per second )

Impact Angle: 15 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 1.68 x 10¹⁸ Joules = 4.00 x 10² MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 8.3 x 10⁴years

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 93400 meters = 307000 ft

The projectile bursts into a cloud of fragments at an altitude of 3660 meters = 12000 ft

The residual velocity of the projectile fragments after the burst is 0.00532 km/s = 0.0033 miles/s

The energy of the airburst is 1.68 x 10¹⁸ Joules = 4.00 x 10² MegaTons.

No crater is formed, although large fragments may strike the surface.

Air Blast:

What does this mean?


The air blast will arrive approximately 1.53 minutes after impact.

Peak Overpressure: 47700 Pa = 0.477 bars = 6.78 psi

Max wind velocity: 94.8 m/s = 212 mph

Sound Intensity: 94 dB (May cause ear pain)

Damage Description:

Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Glass windows will shatter.

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

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.