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
Super-Earth reported. Another Super-Earth, K2-155d, is discovered. In July 2018, the discovery of 40 Eridani b was announced. At 16 light-years it is the closest super-Earth known, and its star is the second-brightest hosting a super-Earth. The Solar System contains no known super-Earths, because Earth is the largest terrestrial planet in the Solar System, and all larger planets both have at least 14 times the mass of Earth and thick gaseous atmospheres without well-defined rocky or watery surfaces; that is, they are either gas giants or ice giants, not terrestrial planets. In January 2016, the existence of a hypothetical super-Earth-mass ninth