Mercury

Mercury is the planet closest to the Sun and its surface looks very much like that of the Moon. This is because they have both been subject to a large number of impacts, especially when the solar system was still young, some 3-4,000 million years ago.
The Caloris Basin has an overall diameter of some 1300 km. Concentric “rings” of mountains cover it - some of these ranges are 30 to 50 km long and form "rims" about 2 km high.
After the impact the enormous crater was partially filled by lava flows. The Caloris Basin has a wrinkled floor, perhaps representing fractures from rapid cooling of this lava. Some older craters that were “flooded” by the lava outpouring from the Caloris impact are also visible.
Altogether, there are more than 20 large, multi-ringed basins on Mercury's surface - many of them are very old and are covered by large numbers of later impact craters.
Mercury's Interior

Although it is rather small, Mercury has a fairly large mass. Its bulk density is there...