Moons · Moon of Mars

Phobos

9,376 km from Mars · Light crosses it in 74 millionths of a second

Across
22 km
Vs Earth
0.17% of Earth
Mass
1.1 × 10¹⁶ kg

Open Phobos in Cosmic Scale

About

Phobos is the larger moon of Mars and orbits closer to its planet than any other moon in the Solar System, only 6,000 km above the surface. It circles faster than Mars turns, so from the ground it rises in the west, twice a day.

Spiralling inward, it will be torn apart by Mars in about 50 million years.

At a glance

SizeAbout 27 × 22 × 18 km
OrbitsMars, every 7.7 hours
Discovered1877, Asaph Hall
Big craterStickney, 9 km wide

Did you know

  1. It is spiralling inward by about 2 m every century and will break into a ring or crash in roughly 50 million years.
  2. Long grooves across it may be stretch marks from Mars's pull.
  3. Japan's MMX mission plans to bring a sample of it back to Earth.

Real photo