Phobos program Phobos program The Phobos (, ) program was an unmanned space mission consisting of two probes launched by the Soviet Union to study Mars and its moons Phobos and Deimos. "Phobos 1" was launched on 7 July 1988, and "Phobos 2" on 12 July 1988, each aboard a Proton-K rocket. "Phobos 1" suffered a terminal failure en route to Mars. "Phobos 2" attained Mars orbit, but contact was lost before the final phase, prior to deployment of a planned Phobos lander. "Phobos 1" and "2" were of a new spacecraft design, succeeding the type used in the "Venera" planetary missions
Planet that objects that fulfill the orbital zone clearance requirement automatically fulfill the roundness requirement. The table below lists Solar System bodies once considered to be planets. Beyond the scientific community, Pluto still holds cultural significance for many in the general public due to its historical classification as a planet from 1930 to 2006. A few astronomers, such as Alan Stern, consider dwarf planets and the larger moons to be planets, based on a purely geophysical definition of "planet". The names for the planets in the Western world are derived from the naming practices of the Romans, which ultimately derive from