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: 492.00 meters ( = 1610.00 feet )

Projectile Density: 1500 kg/m³

Impact Velocity: 72.00 km per second ( = 44.70 miles per second ) (Your chosen velocity is higher than the maximum for an object orbiting the sun)

Impact Angle: 90 degrees

Target Density: 2750 kg/m³

Target Type: Crystalline Rock

Energy:

Energy before atmospheric entry: 2.42 x 10²⁰ Joules = 5.79 x 10⁴ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 5.1 x 10⁵years

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 95600 meters = 314000 ft

The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 70 km/s = 43.5 miles/s

The energy lost in the atmosphere is 1.30 x 10¹⁹ Joules = 3.12 x 10³ MegaTons.

The impact energy is 2.29 x 10²⁰ Joules = 5.48 x 10⁴MegaTons.

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 0.763 km by 0.763 km

Crater Dimensions:

What does this mean?

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

Transient Crater Diameter: 9.79 km ( = 6.08 miles )

Transient Crater Depth: 3.46 km ( = 2.15 miles )

Final Crater Diameter: 13.2 km ( = 8.23 miles )

Final Crater Depth: 644 meters ( = 2110 feet )

The crater formed is a complex crater.

The volume of the target melted or vaporized is 2.04 km³ = 0.49 miles³

Roughly half the melt remains in the crater, where its average thickness is 27.1 meters ( = 89 feet ).

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.