Reference image
Object guide
Deimos is Mars' smaller, outer moon. It has a smoother appearance due to loose regolith infilling craters and orbits far enough from Mars to have a slow apparent motion across the sky. Deimos is approximately 12.4 km across.
How to observe Deimos
Deimos is resolved as a separate world mainly through imaging or spacecraft data; visually, its relationship to mars is the key observing context.
Scientific context
Useful scale comparisons are 0.001 Earth diameters, 0 g surface gravity, 0.003 Earth years per orbit. These values are rounded from the catalogue measurements shown on this page.
- Radius
- 6.2 km
- Diameter
- 12.4 km
- Mass
- 1,476,200,000,000,000 kg
- Mean density
- 1.479 g/cm³
- Surface gravity
- 0.003 m/s² (0 g)
- Orbital period
- 1.2624 days (0.003 years)
- Parent body
- mars
0.001 Earth diameters0 g surface gravity0.003 Earth years per orbit
Source: NASA Science (checked 2026-08-09). Values are rounded catalogue measurements.
Interactive orbit model
Aug 13, 2026, 22:251×
Calculated positions / separate exploration scales