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Length & distance

Just how long is 50 kilometres?

Our planet

50 km

Scale
50 kilometres

The quantity is exact as entered.

50 kmLength
0 - shared origin
Phobos

Phobos is the larger and innermost moon of Mars, notable for its irregular shape and heavily cratered surface.

22.53 kmRepresentative mean diameter
0 - shared origin

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.

A little perspective

50 kilometres is about 2.22 times the mean diameter of Phobos.

Measurements, assumptions & sources +

50 kilometres

Length: 50 km; definition.

The quantity is exact as entered. Comparisons use the clearly stated specimen, model or nominal measurement.

NIST — SI conversion factors

Phobos

Representative mean diameter: 22.53 km; approximate; range 18 km–27 km.

Mars’s larger moon is irregular, about 27 × 22 × 18 km. The 22.533 km comparison diameter is representative rather than a spherical edge.

NASA — Phobos

The marked representative mean diameter is calibrated. Unmeasured illustration details are representative.

Measurement details

Why these numbers?

Compare 50 kilometres with the mean diameter of Phobos. The notes below explain how each value was chosen.

50 kilometres

50 km

Length · definition

The quantity is exact as entered. Comparisons use the clearly stated specimen, model or nominal measurement.

Phobos

22.53 km

Representative mean diameter · approximate · range 18 km–27 km

Mars’s larger moon is irregular, about 27 × 22 × 18 km. The 22.533 km comparison diameter is representative rather than a spherical edge.

Comparing
Length ↔ Representative mean diameter
Relative size
50 kilometres is about 2.22 times the mean diameter of Phobos. 50 kilometres is approximately 122% greater than the mean diameter of Phobos.

How to read the visual

The diagram uses the recorded measurements. Details outside the marked spans do not set the scale.

  • We use 22.53 km for the mean diameter of Phobos; the recorded range is 18 km–27 km.
  • The mean diameter of Phobos: This is an estimate; check the notes for its rounding and uncertainty.

This comparison follows the selected length only; other dimensions may differ.

50,000 mmetres
164,040 ftfeet
31.069 mimiles
3.3423 × 10⁻⁷ AUastronomical units

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