Question 1

True or false: Deimos is named after the Greek god of terror and dread.

Accepted Answer

True. Deimos means 'dread' in Greek; he was a son of Ares (Mars) and twin brother of Phobos (fear).

Question 2

True or false: Deimos is the largest moon of Mars, bigger than Phobos.

Accepted Answer

False. Phobos is larger (about 27 km across) while Deimos is only about 15 km—making Phobos the bigger Martian moon.

Question 3

True or false: Deimos was discovered by the same astronomer who found Uranus.

Accepted Answer

False. William Herschel discovered Uranus, but Asaph Hall discovered both Deimos and Phobos in 1877.

Question 4

True or false: Deimos appears from Mars to be about the same size as Earth's Moon appears from Earth.

Accepted Answer

False. Deimos looks much smaller—like a bright star—because it's tiny and orbits farther out than Phobos.

Question 5

True or false: Deimos takes less than 8 hours to orbit Mars once.

Accepted Answer

False. Deimos orbits Mars in about 30.3 hours—much slower than Phobos, which zips around in under 8 hours.

Question 6

True or false: Deimos has a nearly circular orbit that lies almost exactly in Mars's equatorial plane.

Accepted Answer

True. Unlike Phobos, Deimos orbits with very low eccentricity and inclination, only 0.93° from the equator.

Question 7

True or false: Deimos has a smooth surface almost completely covered by a thick layer of regolith.

Accepted Answer

True. Its low gravity allows dust to settle evenly, giving Deimos a blanketed, crater-smoothed appearance unlike Phobos.

Question 8

True or false: Deimos is slowly spiraling away from Mars and will eventually escape its orbit.

Accepted Answer

True. Like our Moon, Deimos is tidally accelerating outward; in billions of years, it may leave Mars's gravity entirely.

Deimos Trivia Questions