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: 19300.00 km ( = 12000.00 miles )

Projectile diameter: 1610.00 km ( = 999.00 miles )

Projectile Density: 8000 kg/m³

Impact Velocity: 70.00 km per second ( = 43.50 miles per second )

Impact Angle: 90 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 4.28 x 10³¹ Joules = 1.02 x 10¹⁶ 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 strongly disturbed by the impact, but loses little mass.

34.61 percent of the Earth is melted

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 127 milliseconds.

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

Crater Dimensions:

What does this mean?

Transient Crater Diameter: 9730 km ( = 6040 miles )

Transient Crater Depth: 3440 km ( = 2140 miles )

Final Crater Diameter: 32300 km ( = 20100 miles )

Final Crater Depth: 6.74 km ( = 4.18 miles )

The final crater is replaced by a large, circular melt province.

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

Melt volume = 3.15 times the crater volume

At this size, the crater forms in its own melt pool.

Thermal Radiation:

What does this mean?

Time for maximum radiation: 16.7 minutes after impact

Your position is inside the fireball.

The fireball appears 673 times larger than the sun

Thermal Exposure: 4.21 x 10¹³ Joules/m²

Duration of Irradiation: 252 hours

Radiant flux (relative to the sun): 46400

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 1.07 hours after impact.

Richter Scale Magnitude: 15.3 (This is greater than any earthquake in recorded history)

Mercalli Scale Intensity at a distance of 19318.39 km:

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.

XI. As X. Rails bent greatly. Underground pipelines completely out of service.

Ejecta:

What does this mean?

Little rocky ejecta reaches this site; fallout is dominated by condensed vapor from the projectile.

Air Blast:

What does this mean?


The air blast will arrive approximately 16.3 hours after impact.

Peak Overpressure: 1.7e+08 Pa = 1700 bars = 24200 psi

Max wind velocity: 10500 m/s = 23500 mph

Sound Intensity: 165 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.