Naming of moons to as "Proserpina". More recently, especially in science-fictional contexts, the Moon has been called by the Latin name "Luna", presumably on the analogy of the Latin names of the planets, or by association with the adjectival form "lunar". In technical terminology, the word-stems "seleno-" (from Greek "selēnē" "moon") and "cynthi-" (from "Cynthia", an epithet of the goddess Artemis) are sometimes used to refer to the Moon, as in "selenography, selenology," and "pericynthion." The moons of Mars (Phobos and Deimos) were named by Asaph Hall in 1878, soon after he discovered them. They are named after the sons of the god
Phobos (moon) presence of voids and indicate that it is not a solid chunk of rock but a porous body. The porosity of Phobos was calculated to be 30% ± 5%, or a quarter to a third being empty. Phobos has been photographed in close-up by several spacecraft whose primary mission has been to photograph Mars. The first was "Mariner 7" in 1969, followed by "Viking 1" in 1977, "Mars Global Surveyor" in 1998 and 2003, "Mars Express" in 2004, 2008, and 2010, and "Mars Reconnaissance Orbiter" in 2007 and 2008. On August 25, 2005, the "Spirit" rover, with an excess of