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: 100.00 km ( = 62.10 miles )

Projectile diameter: 30.00 meters ( = 98.40 feet )

Projectile Density: 8000 kg/m³

Impact Velocity: 15.00 km per second ( = 9.32 miles per second )

Impact Angle: 45 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 1.27 x 10¹⁶ Joules = 3.04 MegaTons TNT

The average interval between impacts of this size somewhere on Earth is 523.0 years

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 12100 meters = 39600 ft

The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 5.88 km/s = 3.65 miles/s

The energy lost in the atmosphere is 1.08 x 10¹⁶ Joules = 2.57 x 10⁰ MegaTons.

The impact energy is 1.96 x 10¹⁵ Joules = 0.47 MegaTons.

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 0.271 km by 0.192 km

Crater Dimensions:

What does this mean?

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

Transient Crater Diameter: 597 meters ( = 1960 feet )

Transient Crater Depth: 211 meters ( = 692 feet )

Final Crater Diameter: 746 meters ( = 2450 feet )

Final Crater Depth: 159 meters ( = 521 feet )

The crater formed is a simple crater

The floor of the crater is underlain by a lens of broken rock debris (breccia) with a maximum thickness of 73.6 meters ( = 241 feet ).

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 20 seconds after impact.

Richter Scale Magnitude: 4.4

Mercalli Scale Intensity at a distance of 100 km:

I. Not felt except by a very few under especially favorable conditions.

II. Felt only by a few persons at rest, especially on upper floors of buildings.

Ejecta:

What does this mean?

Most ejecta is blocked by Earth's atmosphere

Air Blast:

What does this mean?


The air blast will arrive approximately 5.05 minutes after impact.

Peak Overpressure: 779 Pa = 0.00779 bars = 0.111 psi

Max wind velocity: 1.83 m/s = 4.09 mph

Sound Intensity: 58 dB (Loud as heavy traffic)

Damage Description:

Glass windows may 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.