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: 20000.00 km ( = 12400.00 miles )

Projectile diameter: 10.00 cm ( = 3.94 inches )

Projectile Density: 187300000000000000000000 kg/m³

Impact Velocity: 1000.00 meters per second ( = 3280.00 feet per second )

Impact Angle: 90 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 4.90 x 10²⁵ Joules = 1.17 x 10¹⁰ 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.

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.

Crater Dimensions:

What does this mean?

Transient Crater Diameter: 10300 km ( = 6380 miles )

Transient Crater Depth: 3630 km ( = 2260 miles )

Final Crater Diameter: 34300 km ( = 21300 miles )

Final Crater Depth: 6.86 km ( = 4.26 miles )

The crater formed is a complex crater.

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 1.11 hours after impact.

Richter Scale Magnitude: 11.3 (This is greater than any earthquake in recorded history)

Mercalli Scale Intensity at a distance of 20000 km:

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.

V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.

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 16.8 hours after impact.

Peak Overpressure: 10500 Pa = 0.105 bars = 1.5 psi

Max wind velocity: 23.8 m/s = 53.3 mph

Sound Intensity: 80 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.