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: 64.40 km ( = 40.00 miles )

Projectile diameter: 341.00 meters ( = 1120.00 feet )

Projectile Density: 1500 kg/m³

Impact Velocity: 17.00 km per second ( = 10.60 miles per second )

Impact Angle: 45 degrees

Target Density: 2750 kg/m³

Target Type: Crystalline Rock

Energy:

Energy before atmospheric entry: 4.51 x 10¹⁸ Joules = 1.08 x 10³ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 6.9 x 10⁴years

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 72500 meters = 238000 ft

The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 15 km/s = 9.29 miles/s

The energy lost in the atmosphere is 1.02 x 10¹⁸ Joules = 2.43 x 10² MegaTons.

The impact energy is 3.50 x 10¹⁸ Joules = 8.36 x 10²MegaTons.

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 1.25 km by 0.886 km

Crater Dimensions:

What does this mean?

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

Transient Crater Diameter: 3.33 km ( = 2.07 miles )

Transient Crater Depth: 1.18 km ( = 0.73 miles )

Final Crater Diameter: 3.91 km ( = 2.43 miles )

Final Crater Depth: 446 meters ( = 1460 feet )

The crater formed is a complex crater.

The volume of the target melted or vaporized is 0.022 km³ = 0.00528 miles³

Roughly half the melt remains in the crater, where its average thickness is 2.53 meters ( = 8.31 feet ).

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 12.9 seconds after impact.

Richter Scale Magnitude: 6.6

Mercalli Scale Intensity at a distance of 64.37 km:

VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.

Ejecta:

What does this mean?


The ejecta will arrive approximately 1.92 minutes after the impact.

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

Average Ejecta Thickness: 4.1 mm ( = 1.61 tenths of an inch )

Mean Fragment Diameter: 7.71 cm ( = 3.04 inches )

Air Blast:

What does this mean?


The air blast will arrive approximately 3.25 minutes after impact.

Peak Overpressure: 15800 Pa = 0.158 bars = 2.24 psi

Max wind velocity: 34.9 m/s = 78.1 mph

Sound Intensity: 84 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.