Asteroid Threats in Context

id Software’s upcoming game Rage uses asteroid Apophis as the scene setter for a post apocalyptic world. (id is part of Zenimax now, which also owns Bethesda, who did Fallout, a similar scene but done with nuclear weapons…)

Is this even close to being realistic? No, because of multiple reasons.

You can check out the list of impact risks maintained by NASA here.

Apophis is zero on the Torino scale. The Torino scale is a balanced impact risk number, from zero to ten. There’s one one on the list at the time of writing. Apophis also has a 270 meter estimated diameter and not a very high velocity, 6 km/s.

We can use the impact effects calculator here for some gauging of what would happen. Even if we assumed it to be dense rock and the impact velocity to be 17 km/s, there wouldn’t be that huge effects (although they could be big locally).

Assuming it hits the ground, at 300 km distance from the impact site you would get a mild earthquake, and a sound as loud as heavy traffic. At 100 km you’d get a stronger earthquake, 6.7 on the Richer scale, and the fireball would be 4 times as bright as the sun. (Still probably no direct skin burns). You would get some sparse gravel ejecta at 100 km which means you wouldn’t want to be outside, but only very little dust ejecta at 300 km.

The main takeaway message is that since the asteroid is so small, the damage would not be widespread. You could not really destroy even two large cities with one. Hence no apocalypse.

If it hit the sea (likely), it could create a tsunami, and that could generate more damage to humans, depending on where it struck (this I don’t know very well), but the Atlantic, Indian Ocean and China Sea are probably very bad. The 2004 Tsunamis triggered by an undersea earthquake killed over 200,000 people.

It’s still very much worth observing and developing technology to prevent large asteroid strikes. It’s just that the public doesn’t seem to have any handle on what the effects are like.