Phobos and Deimos in fiction Phobos and Deimos in fiction Mars has two moons, Phobos and Deimos. Due to their small size, both moons were discovered only in 1877, by astronomer Asaph Hall. Nevertheless, they frequently feature in works of science fiction. Some of the earliest mentions of Mars's moons in fiction predate their discovery. In Jonathan Swift's famous satire "Gulliver's Travels" (1726), the astronomers of flying island Laputa are described as having discovered two satellites of Mars. Voltaire's short story "Micromégas" (1752), about alien visitors from Sirius and Saturn, also describes Mars as having two moons. Voltaire is thought to have been influenced by
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