Usually, the core of a planet will be either molten or solid rock, or plasma of some sort. Depends on the planet and it's closeness to it's sun.
Volcanism can only occur on planets with a liquid mantle.
Mars and Venus
Neptune and Uranus
The interiors of Jovian planets (Jupiter, Saturn, Uranus, Neptune) differ due to variations in composition, temperature, and pressure. These factors influence the formation of different layers within the planets, such as metallic hydrogen in Jupiter and Saturn, icy layers in Uranus and Neptune, and rocky cores in all four Jovian planets. The planets' formation and evolutionary history also contribute to their interior differences.
Tidal forces generated by gravitational interactions with their parent planet is a significant source of heat in the interiors of moons orbiting close to giant planets. These tidal forces create friction within the moon's interior, generating heat through tidal heating.
The moons of the outer planets generally have rocky interiors and exteriors made of ice. Rock, particularly silicate rock, is quite abundant because silicon and oxygen are fairly common elements.
All planets have a core.
Gas giant planets, such as Jupiter and Saturn, are primarily made of hydrogen and helium gases. These planets have thick atmospheres composed mainly of these gases, with solid cores deep in their interiors.
"Gas" seems the obvious answer, but it's not quite that simple. Jupiter and Saturn have a lot of liquid hydrogen. They probably have rocky cores as well. Uranus and Neptune have different interiors from Jupiter and Saturn. They probably have a lot of water, ammonia, and methane in liquid or solid form. Still, the thing ALL the gas planets have is gas. The most common gas is hydrogen.
Yes all planets have a orbit
Meteorites crashed into all of the planets.
No not all the planets have craters on.