Facts about Phobos (Mars's moon)
- 08
Mars's moon Phobos has an extremely low density, suggesting it may be a rubble pile with significant internal voids rather than solid rock.
- 07
Tidal heating from Mars's gravity causes Phobos to experience internal stress, making it one of the few moons in the solar system where moonquakes occur regularly due to orbital mechanics rather than volcanic activity.
- 06
Scientists believe Phobos originated as a captured asteroid rather than forming alongside Mars, based on its composition and irregular shape differing from Martian material.
- 05
Phobos's heavily cratered surface bears the distinctive 9-kilometer-wide Stickney crater, named after astronomer Asaph Hall's wife.
- 04
Phobos completes one orbit around Mars every 7 hours and 39 minutes, making it the only moon in our solar system that orbits faster than its parent planet rotates.
- 03
In 1877, American astronomer Asaph Hall discovered Phobos orbiting Mars at a distance of only 9,376 kilometers from the planet's center, closer than any other moon to its parent planet in the solar system.
- 02
Phobos measures only 22.2 kilometers across its longest axis, making Mars's larger moon smaller than Earth's Mount Everest is tall.
- 01
Orbital decay will eventually destroy Phobos within 30 to 50 million years as it spirals toward Mars due to tidal forces.