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: 12000.00 km ( = 7450.00 miles )

Projectile diameter: 2.70 km ( = 1.68 miles )

Projectile Density: 7874 kg/m³

Impact Velocity: 4.00 km per second ( = 2.48 miles per second )

Impact Angle: 90 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 6.49 x 10²⁰ Joules = 1.55 x 10⁵ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.7 x 10⁶years

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.

Crater Dimensions:

What does this mean?

Transient Crater Diameter: 18.8 km ( = 11.7 miles )

Transient Crater Depth: 6.65 km ( = 4.13 miles )

Final Crater Diameter: 27.7 km ( = 17.2 miles )

Final Crater Depth: 804 meters ( = 2640 feet )

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 40 minutes after impact.

Richter Scale Magnitude: 8.1

Mercalli Scale Intensity at a distance of 12000 km:

Nothing would be felt. However, seismic equipment may still detect the shaking.

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 10.1 hours after impact.

Peak Overpressure: 246 Pa = 0.00246 bars = 0.0349 psi

Max wind velocity: 0.579 m/s = 1.3 mph

Sound Intensity: 48 dB (Easily Heard)

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.