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: 10.00 meters ( = 32.80 feet )

Projectile Density: 8000 kg/m³

Impact Velocity: 7.50 km per second ( = 4.66 miles per second )

Impact Angle: 90 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 1.18 x 10¹⁴ Joules = 0.28 x 10^-1 MegaTons TNT

The average interval between impacts of this size somewhere on Earth is 24.7 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 -54.8 meters = -180 ft

The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 6.46 km/s = 4.01 miles/s

The energy lost in the atmosphere is 3.05 x 10¹³ Joules = 0.73 x 10^-2 MegaTons.

The impact energy is 8.73 x 10¹³ Joules = 0.21 x 10^-1MegaTons.

The larger of these two energies is used to estimate the airblast damage.

The broken projectile fragments strike the ground in an ellipse of dimension 0.01 km by 0.01 km

Crater Dimensions:

What does this mean?

Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.

Transient Crater Diameter: 296 meters ( = 972 feet )

Transient Crater Depth: 105 meters ( = 344 feet )

Final Crater Diameter: 370 meters ( = 1210 feet )

Final Crater Depth: 78.8 meters ( = 259 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 36.5 meters ( = 120 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: 3.5

Mercalli Scale Intensity at a distance of 1 km:

III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck.

IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

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: 48500 Pa = 0.485 bars = 6.88 psi

Max wind velocity: 96 m/s = 215 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.