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 · representative mean diameter
Representative mean diameter · approximate
Typical recorded range: 10 km to 15 km.
A little perspective
Deimos vs Challenger Deep: length comparison
The mean diameter of Deimos is about 1.13 times the depth of Challenger Deep.
Deimos is the smaller and outermost natural satellite of Mars, with an irregular, rocky shape.
Challenger Deep is the deepest known point in the Earth's oceans, located in the Mariana Trench.
Both rulers start at the same zero and share one linear scale. Artwork keeps its original proportions. A ruler represents the selected distance or a measurement not visible in this view.
Measurements, assumptions & sources +
Deimos
Representative mean diameter: 12.4 km; approximate; range 10 km–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 representative mean diameter is calibrated. Unmeasured illustration details are representative.
Challenger Deep
Depth: 10.94 km; approximate.
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.
Use the visual comparison to explore its scale, then check the measurements and sources.
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Why this measurement?
Why we use 12.4 km
We compare the mean diameter of Deimos. This is an estimate; check the notes for its rounding and uncertainty. 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 measured feature, not the edges of the image. How calibrated comparisons work →
Recorded properties
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
Explore nearby values.
Compare examples with lower, similar and higher values. Each card names the measurement being compared.
Nearest lower valuePlaces and natural featuresChallenger Deep10.94 kmDepthChallenger Deep is the deepest known point in the Earth's oceans, located in the Mariana Trench.
Around the same scalePlanets, moons and spaceAdrastea16.4 kmMean-equivalent diameterAdrastea is a small, irregular inner moon of Jupiter, located just outside the planet's main ring.
Nearest higher valuePlanets, moons and spacePhobos22.53 kmRepresentative mean diameterPhobos 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.
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