Deimos
Deimos is the smaller and outermost natural satellite of Mars, with an irregular, rocky shape.
Also known as: Mars II
How big is it?
12.4 km across
Representative mean diameter · approximate
Typical recorded range: 10 km to 15 km.
A little perspective
About the same scale as Challenger Deep.
Challenger Deep: Challenger Deep is the deepest known point in the Earth's oceans, located in the Mariana Trench.
Measurements, assumptions & sources +
Deimos
Mars’s smaller moon is irregular, roughly 15 × 12 × 11 km. The 12.4 km diameter is a representative comparison span rather than a hard spherical edge.
The marked representative mean diameter is calibrated. Unmeasured illustration details are representative.
Challenger Deep
About 10,935 m below the ocean surface in the Mariana Trench. Depth estimates vary by survey. The line shows depth, not the trench’s width.
The marked depth is calibrated. Unmeasured illustration details are representative.
Change your perspective
Put it next to…
Choose a suggestion to redraw the comparison, or open its page to learn what it is.
Why this measurement?
Why we use 12.4 km
For comparison, this page uses representative mean diameter. This is labelled approximate; the central value is useful for comparison, while real values or measurement solutions can vary. The recorded range is 10 km to 15 km.
Mars’s smaller moon is irregular, roughly 15 × 12 × 11 km. The 12.4 km diameter is a representative comparison span rather than a hard spherical edge.
The marked horizontal span follows the named feature; transparent margins and unmeasured details do not alter it. How calibrated comparisons work →
Recorded properties
Deimos dimensions and measurements
| Property | Selected value | Recorded range | Basis |
|---|---|---|---|
| 12.4 km | 10 km to 15 km | approximate | |
| 1.476 × 10¹² t | 1.4 × 10¹² t to 1.6 × 10¹² t | approximate |
Around this scale
Go smaller. Go bigger.
These links use compatible length records, ordered around the selected value.
Nearest lower value · PlacesChallenger Deep10.94 kmChallenger Deep is the deepest known point in the Earth's oceans, located in the Mariana Trench.
Around the same scale · SpaceAdrastea16.4 kmAdrastea is a small, irregular inner moon of Jupiter, located just outside the planet's main ring.
Nearest higher value · SpacePhobos22.53 kmPhobos is the larger and innermost moon of Mars, notable for its irregular shape and heavily cratered surface.Sources and method
Want to check the number?
The source records and measurement method remain available for inspection.
- NASA — DeimosMars’s smaller moon is an irregular body approximately 15 × 12 × 11 km.
There’s always another scale
Follow your curiosity.
SpaceMars6,779 kmMars is a rocky planet orbiting the Sun, with a reddish surface due to iron oxide.SpacePhobos22.53 kmPhobos is the larger and innermost moon of Mars, notable for its irregular shape and heavily cratered surface.
SpaceMoon3,475 kmThe Moon is Earth’s natural satellite and the brightest large object in Earth’s night sky.PlacesChallenger Deep10.94 kmChallenger Deep is the deepest known point in the Earth's oceans, located in the Mariana Trench.
SpaceNeutron star20 kmA neutron star is the dense remnant core left after a massive star explodes as a supernova, composed mostly of neutrons.PeopleOne-hour cycle20 kmA one-hour cycle is the distance covered by cycling at a constant speed for one hour without stopping.
Places100 km² island100 km²An island is a landmass entirely surrounded by water.PeopleOne-hour walk5 kmA one-hour walk is the distance a person travels by walking continuously at a steady pace for one hour.