Fictional planets of the Solar System 40 Eridani A. Counter-Earth was a hypothetical planet sharing an orbit with Earth, but on the opposite side of the Sun (hence Earth and Counter-Earth would always be invisible to each other). The idea of a counter-Earth has never been a serious scientific hypothesis in modern times. Phaëton is a name given to a supposed planet existing in the past between the orbits of Mars and Jupiter, which no longer exists, having become the Solar System's asteroid belt. Proposed not long after the discovery of multiple asteroids at the beginning of the 19th century, the idea that the asteroids were
Aonia Terra Aonia Terra Aonia Terra is a region in the southern hemisphere of the planet Mars. It is named after a classical albedo feature, the "Bay of the Muses" and its name was approved in 1979, by the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature. It is centered at and covers 3900 km at its broadest extent. It covers latitudes 30 to 81 South and longitudes 60 to 163 W. Aonia Terra is an upland area notable for massive cratering including the large Lowell Crater, parts of the region features small craters, in the plain areas, Thaumasia Fossae