These dominant planetesimals had now become planetsized bodies with masses ranging between that of Earth and about 1/20 of that value. They were to become the terrestrial planets. Mercury, Venus, Earth, and Mars are the surviving terrestrial planets. Planetary scientists think that one or two others may have formed in the young Solar System but were later destroyed. (As you will see later in this section, one of them may have been responsible for the creation of Earth’s Moon.)