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: 1000.00 meters ( = 3280.00 feet )

Projectile diameter: 3.00 meters ( = 9.84 feet )

Projectile Density: 8000 kg/m³

Impact Velocity: 7.80 km per second ( = 4.84 miles per second )

Impact Angle: 45 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 3.44 x 10¹² Joules = 0.82 x 10^-3 MegaTons TNT

The average interval between impacts of this size somewhere on Earth is 0.9 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 lands intact, with a velocity 3.85 km/s = 2.39 miles/s.

The energy lost in the atmosphere is 2.60 x 10¹² Joules = 0.62 x 10^-3 MegaTons.

Crater Dimensions:

What does this mean?

Transient Crater Diameter: 82.2 meters ( = 269 feet )

Transient Crater Depth: 29.1 meters ( = 95.3 feet )

Final Crater Diameter: 103 meters ( = 337 feet )

Final Crater Depth: 21.9 meters ( = 71.7 feet )

The crater formed is a simple crater

The floor of the crater is underlain by a lens of broken rock debris (breccia) with a maximum thickness of 10.1 meters ( = 33.2 feet ).

At this impact velocity ( < 12 km/s), little shock melting of the target occurs.

Thermal Radiation:

What does this mean?

At this impact velocity ( < 15 km/s), little vaporization occurs; no fireball is created, therefore, there is no thermal radiation damage.

Seismic Effects:

What does this mean?


The major seismic shaking will arrive approximately 200 milliseconds after impact.

Richter Scale Magnitude: 2.1

Mercalli Scale Intensity at a distance of 1 km:

I. Not felt except by a very few under especially favorable conditions.

II. Felt only by a few persons at rest, especially on upper floors of buildings.

Ejecta:

What does this mean?

Most ejecta is blocked by Earth's atmosphere

Air Blast:

What does this mean?


The air blast will arrive approximately 3.03 seconds after impact.

Peak Overpressure: 6910 Pa = 0.0691 bars = 0.981 psi

Max wind velocity: 15.8 m/s = 35.4 mph

Sound Intensity: 77 dB (Loud as heavy traffic)

Damage Description:

Glass windows will shatter.

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.