Impact Effects

Gareth Collins, Robert Marcus, and H. Jay Melosh

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

Click each effect button (e.g. "Crater") to see the extent of each impact effect!

Your Inputs:

Projectile diameter: 90.00 meters ( = 295.00 feet )

Projectile Density: 3000 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: 1.65 x 10¹⁷ Joules = 3.95 x 10¹ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 4.5 x 10³years

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 54000 meters = 177000 ft

The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 4.78 km/s = 2.97 miles/s

The energy lost in the atmosphere is 1.52 x 10¹⁷ Joules = 3.64 x 10¹ MegaTons.

The impact energy is 1.31 x 10¹⁶ Joules = 3.12 MegaTons.

The larger of these two energies is used to calculate the airblast damage.

The broken projectile fragments strike the ground in an ellipse of dimension 0.808 km by 0.571 km

Crater Dimensions:

What does this mean?

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

Transient Crater Diameter: 896 meters ( = 2940 feet )

Transient Crater Depth: 317 meters ( = 1040 feet )

Final Crater Diameter: 1.12 km ( = 0.696 miles )

Final Crater Depth: 238 meters ( = 782 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 111 meters ( = 363 feet ).

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

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.