Deimos is composed of carbon-rich rock, much like C-type (carbonaceous chondrite) asteroids, and ice. It is heavily cratered. It is probably an asteroid that was perturbed by Jupiter into an orbit that allowed it to be captured by Mars, though this theory is still in some dispute.
- Orbital radius: 23,459 km
- Diameter: 12.6 km (15 x 12.2 x 11)
- Mass: 1.8×1015 kg
- Density: 1.7 g/cm3
- Orbital period: 1.26244 days
- Orbital inclination: 0.9-2.7°