The Densest Planted in the Solar System?

We know a lot about the Earth's core, because we can do things like study earthquakes. We don't have those kind of sensors on Mars now and on the moon. The other ones we're guessing a little bit more. Density here is really connected to size. As you add more stuff to the planet, it doesn't just get bigger. So for rocky planets, there's no maximum density unless you think about black hole levels but there is probably a maximum size.