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 the autumnal equinox and the vernal equinox, while farther from the equator they happen closer to the winter solstice. Observers at high latitudes (but less than 70.4°) will see a noticeably smaller angular diameter for Phobos because they are considerably farther away from it than observers at Mars's equator. As a result, transits of Phobos for such observers will cover less of the Sun's disk. Because it orbits so close to Mars, Phobos cannot be seen north of 70.4°N or south of 70.4°S; observers at such latitudes will obviously not see transits, either. Mars Rover "Opportunity" rover photographed transits of