Phobos (mythology) of Cypselus on the shield of Agamemnon. American astronomer Asaph Hall named a satellite of the planet Mars, "Phobos", which he discovered along with the second Mars satellite, "Deimos", in 1877. Phobos is the larger of the two satellites. The word "phobia" derives from "phobos", (Φόβος), meaning fear. The two brothers Deimos and Phobos were particularly worshipped in the city state of "Sparta" as they were the sons of Ares, the god of war. Phobos in Greek literally means "fear" (). Spartan soldiers would idolize Phobos, because he symbolized discipline, and consistency of the armed forces. Because Phobos and Deimos
Transit of Phobos from Mars transit of Phobos from Mars usually lasts only thirty seconds or so, due to the moon's very rapid orbital period of about 7.6 hours. Because Phobos orbits close to Mars and in line with its equator, transits of Phobos occur somewhere on Mars on most days of the Martian year. Its orbital inclination is 1.08°, so the latitude of its shadow projected onto the Martian surface shows a seasonal variation, moving from 70.4°S to 70.4°N and back again over the course of a Martian year. Phobos is so close to Mars that it is not visible south of 70.4°S or