Cometary orbits are not steady and orderly like planetary orbits.
Comets can come from anyhere on any trajectory.
The chances of a planet getting in the way are pretty good, especially since a planet’s gravity will draw a nearby comet toward it.
On June 30, 1908, a comet was reported to have crashed in Russia’s Siberian wilderness.
Recent reports have raised a question as to whether it was a comet or an asteroid.
Its nucleus vaporized in the atmosphere, but the tremors from its impact were detected.
Halley’s comet, probably the most popularly famous comet, completes a single orbit around the Sun about every 76 years.
It will next be at its closest point to the Sun in the year 2061.