Impact probabilities are probabilities because there are uncertainties in the orbits themselves, as well as in the simulation or propagation. The Palermo scale quantifies a given object's threat to Earth in the foreseeable future.
If you visit JPL CNEOS Sentry and use unconstrained settings, it shows only a few objects with more than 1 chance in 1000 to hit Earth in the next 100 years, and most of those are small.įew NEO orbits are known precisely enough to make meaningful predictions beyond that. The asteroid risk is real, but we should not overstate it.
The short observation arcs make their pre-impact orbits highly uncertain, so a few small bodies spread within $\pm\sigma$ of each orbital element value may improve your chances.Īlternatively you could set an object up for immediate collision with Earth at a relative speed of 12 to 20 km/s in any direction, and run the simulator backward to see how it would get there. If you're already modeling real asteroids, try some which have hit Earth: In a simulation, the timestep should also be short enough to detect a collision.Īn object at a moderate relative speed of 10 km/s crosses Earth's diameter in about 20 minutes a longer timestep could turn a hit into a miss. A NEO only impacts Earth if both bodies are in the orbit intersection zone at the same time, closely enough for gravity $(F \propto 1/r^2)$ to bring them in contact.