In what year were Phobos and Deimos discovered?

Phobos and Deimos were discovered in 1877 by American astronomer Asaph Hall. He found Deimos on August 12 and Phobos on August 18 while observing Mars at the United States Naval Observatory in Washington, D.C.

Hall searched during Mars's especially favorable close approach in 1877. His wife, Angeline Stickney, encouraged him to continue looking after he nearly abandoned the difficult search. The discoveries were made with the observatory's 26-inch Great Equatorial refracting telescope, then the world's largest refracting telescope.

Phobos is the larger and innermost moon, while Deimos is smaller and farther from Mars. Their names come from Greek mythology: Phobos personified fear and panic, and Deimos personified terror. Both were companions of Ares, the Greek counterpart of the Roman god Mars.

The year is sometimes confused with the dates of later observations or orbital studies. Hall's discovery of both Martian moons, however, firmly belongs to 1877. Their tiny apparent size and close proximity to bright Mars explain why earlier astronomers had failed to spot them.