[evan_au (OP)]

In a discussion on the age of the Solar System, it was suggested that you could count craters on the planets; Jupiter was mentioned as an example.

Fragments of the comet Shoemaker-Levy made a big splash on Jupiter, leaving behind a mark thousands of kilometers wide:

However, these surface marks were rapidly swallowed by Jupiter's swirling, deep atmosphere.
- I imagine that dust from these large impacts would eventually rain down through Jupiter's atmosphere

To count comet impacts, you really need rocky planets, dwarf planets or moons.
- Even Earth is not a good example, as weathering and plate tectonics gradually erase the scars of old impacts.