Terrestrial planet Terrestrial planet A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun, i.e. Mercury, Venus, Earth, and Mars. The terms "terrestrial planet" and "telluric planet" are derived from Latin words for Earth ("Terra" and "Tellus"), as these planets are, in terms of structure, "Earth-like". Terrestrial planets have a solid planetary surface, making them substantially different from the larger giant planets, which are composed mostly of some combination of hydrogen, helium, and water existing in various
Planet Nine distant orbits around another star, or rogue planet, leaving one in a stable orbit around the Sun via a process similar to the capture of irregular satellites around the giant planets. If the planet originated in a system with a number of Neptune-massed planets, and without Jupiter-massed planets, it could be scattered into a more long-lasting distant eccentric orbit, increasing its chances of capture. Although the odds of the Sun capturing another planet from another star can be higher, a wider variety of orbits are possible, reducing the probability of a planet being captured on an orbit like that proposed