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: 5000.00 km ( = 3110.00 miles )

Projectile diameter: 500.00 km ( = 311.00 miles )

Projectile Density: 8000 kg/m³

Impact Velocity: 20.00 km per second ( = 12.40 miles per second )

Impact Angle: 1 degrees

Target Density: 2750 kg/m³

Target Type: Crystalline Rock

Energy:

Energy before atmospheric entry: 1.05 x 10²⁹ Joules = 2.50 x 10¹³ MegaTons TNT

The average interval between impacts of this size is longer than the Earth's age.

Such impacts could only occur during the accumulation of the Earth, between 4.5 and 4 billion years ago.

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).

Depending on the direction and location of impact, the collision may cause a change in the length of the day of up to 13.6 minutes.

The impact does not shift the Earth's orbit noticeably.

Crater Dimensions:

What does this mean?

Transient Crater Diameter: 566 km ( = 352 miles )

Transient Crater Depth: 200 km ( = 124 miles )

Final Crater Diameter: 1300 km ( = 806 miles )

Final Crater Depth: 2.56 km ( = 1.59 miles )

The crater formed is a complex crater.

The volume of the target melted or vaporized is 1.63e+07 km³ = 3.9e+06 miles³

Roughly half the melt remains in the crater, where its average thickness is 64.6 km ( = 40.1 miles ).

Thermal Radiation:

What does this mean?

Time for maximum radiation: 7.86 minutes after impact

Your position is inside the fireball.

The fireball appears 344 times larger than the sun

Thermal Exposure: 1.50 x 10¹² Joules/m²

Duration of Irradiation: 34 hours

Radiant flux (relative to the sun): 12200

Effects of Thermal Radiation:

Clothing ignites

Much of the body suffers third degree burns

Newspaper ignites

Plywood flames

Deciduous trees ignite

Grass ignites

Seismic Effects:

What does this mean?


The major seismic shaking will arrive approximately 16.7 minutes after impact.

Richter Scale Magnitude: 13.6 (This is greater than any earthquake in recorded history)

Mercalli Scale Intensity at a distance of 5000 km:

IX. General panic. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in ground. In alluviated areas sand and mud ejected, earthquake fountains, sand craters.

X. Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, etc. Sand and mud shifted horizontally on beaches and flat land. Rails bent slightly.

Ejecta:

What does this mean?


The ejecta will arrive approximately 26.2 minutes after the impact.

At your position there is a fine dusting of ejecta with occasional larger fragments

Average Ejecta Thickness: 7.35 meters ( = 24.1 feet )

Mean Fragment Diameter: 298 microns ( = 11.8 thousandths of an inch )

Air Blast:

What does this mean?


The air blast will arrive approximately 4.21 hours after impact.

Peak Overpressure: 3.82e+07 Pa = 382 bars = 5420 psi

Max wind velocity: 4970 m/s = 11100 mph

Sound Intensity: 152 dB (Dangerously Loud)

Damage Description:

Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.

Highway truss bridges will collapse.

Highway girder bridges will collapse.

Glass windows will shatter.

Cars and trucks will be largely displaced and grossly distorted and will require rebuilding before use.

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.