# Earth Impact Effects

Here’s a follow up to my post yesterday on the asteroid Apophis. JPL has an interesting little calculator for calculating the effects of celestial bodies impacting with Earth.

After plugging in the parameters that Neal deGrasse Tyson mentioned (100m in diameter, impacting 500 miles away – in 3 miles of ocean), it yielded some pretty insignificant results (besides the tsunami that would be generated).

Distance from Impact: 805.00 km = 499.90 miles

Projectile Diameter: 100.00 m = 328.00 ft = 0.06 miles

Projectile Density: 3000 kg/m3

Impact Velocity: 17.00 km/s = 10.56 miles/s

Impact Angle: 45 degrees

Target Density: 1000 kg/m3

Target Type: Liquid Water of depth 4.57 meters, over typical rock.

Energy:

Energy before atmospheric entry: 2.27 x 1017 Joules = 5.42 x 101 MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 2.4 x 103years

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 6.66 km/s = 4.14 miles/s

The impact energy is 3.49 x 1016 Joules = 8.33 MegaTons.

The broken projectile fragments strike the ground in an ellipse of dimension 0.81 km by 0.573 km

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 Earth’s rotation period or the tilt of its axis.

The impact does not shift the Earth’s orbit noticeably.

Crater Dimensions:

What does this mean?

The crater opened in the water has a diameter of 1.85 km = 1.15 miles

For the crater formed in the seafloor:

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

Transient Crater Diameter: 1.12 km = 0.695 miles

Transient Crater Depth: 0.396 km = 0.246 miles

Final Crater Diameter: 1.4 km = 0.869 miles

Final Crater Depth: 0.298 km = 0.185 miles

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 138 m = 454 ft.

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

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 at approximately 161 seconds.

Richter Scale Magnitude: 5.2

Mercalli Scale Intensity at a distance of 805 km:

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

Ejecta:

What does this mean?

Most ejecta is blocked by Earth’s atmosphere

Air Blast:

What does this mean?

The air blast will arrive at approximately 2440 seconds.

Peak Overpressure: 138 Pa = 0.00138 bars = 0.0195 psi

Max wind velocity: 0.324 m/s = 0.725 mph

Sound Intensity: 43 dB (Easily Heard)

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