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
Sagan Planet Walk obelisk for Neptune is located just across the bridge in Conley Park. The Planet Walk was conceived and built prior to Pluto losing its planetary status in 2006, and the model includes the Pluto Obelisk, which is located just outside the Sciencenter on First street. The model was expanded in 2012 to include Alpha Centauri, the star closest to the Sun. The Alpha Centauri Obelisk is exhibited at the ‘‘Imiloa Astronomy Center of Hawai‘i at the University of Hawaii in Hilo, Hawaii. This extension made the Sagan Planet Walk the world's largest exhibition. Television host and former student of Carl