Question 1

True or false: Phobos has a thin atmosphere made mostly of carbon dioxide, similar to Mars.

Accepted Answer

False. Phobos has no atmosphere; it's too small to retain one. Any gases would quickly escape into space.

Question 2

True or false: Phobos is large enough that its own gravity makes it spherical in shape.

Accepted Answer

False. Phobos is irregular and potato-shaped, about 27 km at its widest. It lacks enough gravity to pull itself into a sphere.

Question 3

True or false: Phobos is one of the darkest moons in the solar system, reflecting less light than coal.

Accepted Answer

True. Phobos has an albedo of about 0.07, making it darker than many asteroids and even coal dust.

Question 4

True or false: Phobos orbits Mars so fast that it rises in the west and sets in the east.

Accepted Answer

True. Phobos completes an orbit in about 7.7 hours, faster than Mars rotates, making it appear to rise in the west.

Question 5

True or false: Phobos is slowly spiraling away from Mars, like our Moon does from Earth.

Accepted Answer

False. Phobos is actually spiraling inward due to tidal forces and will eventually crash into Mars or break apart in about 30-50 million years.

Question 6

True or false: Phobos is thought to be a captured asteroid from the main asteroid belt between Mars and Jupiter.

Accepted Answer

True. Phobos's composition resembles carbonaceous chondrite asteroids, supporting the capture theory, though some debate exists.

Question 7

True or false: Phobos was discovered by the same astronomer who found the moons of Jupiter.

Accepted Answer

False. Asaph Hall discovered Phobos in 1877. Galileo discovered Jupiter's moons, but Hall found Phobos and Deimos using the U.S. Naval Observatory telescope.

Question 8

True or false: Phobos has a giant crater called Stickney, named after the maiden name of its discoverer's wife.

Accepted Answer

True. Stickney was the maiden name of Asaph Hall's wife, who encouraged him to continue his search for Martian moons.

Phobos Trivia Questions