How big must an asteroid be to cause global damage?

Roughly 1 km or larger. The Chicxulub impactor (~10 km) caused a mass extinction. A 100 m asteroid would devastate a city or region.

What is a typical impact velocity?

For near-Earth asteroids: 15-25 km/s. Long-period comets can hit at 40-70 km/s, greatly increasing energy.

Tunguska-class events (~50 m): every few hundred years. Chicxulub-class (~10 km): every ~100 million years.

Estimate the kinetic energy of an asteroid impact from its diameter, density, and velocity: KE = 0.5 * (pi/6) * d^3 * rho * v^2.

Asteroid Diameter

Density

kg/m³

Impact Velocity

m/s

Impact Energy

314,159,265,358,979,260.000 J

Asteroid Mass1,570,796,327 kg

Energy (megatons TNT)75.09 Mt

Impact Energy vs Asteroid Diameter

The kinetic energy of a spherical impactor:

KE = 0.5 × m × v²

where m = (π/6) × d³ × ρ (sphere mass)

d = diameter

ρ = density (rock: ~3000, iron: ~7800 kg/m³)

v = impact velocity (typical 15-25 km/s for near-Earth asteroids)

1 megaton TNT = 4.184 × 10¹⁵ J. The Chicxulub impactor (~10 km) released ~10¹⁴ Mt.

A 100 m rocky asteroid at 20 km/s.

Calculate escape velocity.

Compare to fusion energy.

Surface gravity of a body.