Research any topic before you write.

Find related topics. | Discover entities. | See connections. | Build a topical map.

Phobos (moon)

Phobos (/ˈfoʊboʊs/) is the innermost and larger of the two natural satellites of Mars, the other being Deimos. The two moons were discovered in 1877 by American astronomer Asaph Hall. Phobos is named after the Greek god of fear and panic, who is the twin brother of Deimos and son of Ares (Mars).

Characters, Physical characteristics & Orbital characteristics

Use the mouse wheel or two fingers (on touchscreens) to zoom in and out of the map.

Research this topic

Explore the main themes, entities and connections around Phobos (moon). Start with the topic map, then use the sections below for research and deeper semantic analysis.

Explore this topic

Start with a few of the strongest sections from the source topic. These are research directions, not a list of keywords you must use.

Key facts & relationships

High-confidence facts extracted from structured source data. Use them as anchors for further research.

Adjectives
Phobian /ˈfoʊbiən/
Albedo
0.071 ± 0.012 at 0.54 μm
Apoapsis
9,517.58 km
Apparent magnitude
11.8
Average orbital speed
2.138 km/s
Axial tilt
0°

Topics to explore

Browse the full topic structure. Each item opens a new analysis centered on that subject.

Overview

Discovery and etymology

Physical characteristics

Orbital characteristics

Origin

Exploration

Advanced semantic analysis

Deeper signals for content research, entity SEO and topical coverage. The plain-language headings explain what each technical view is useful for.

Map overview Semantic statistics

Phobos (moon)

Nodes160
Edges159
Triples31
Avg. degree1.99
Density0.0125
Components1

How this topic connects Entity context

See the strongest relationship patterns around the current topic before diving into the raw triples.

Phobos (moon)

Top relations

Adjectives · 1
Phobos (moon) → Phobian /ˈfoʊbiən/
Albedo · 1
Phobos (moon) → 0.071 ± 0.012 at 0.54 μm
Apoapsis · 1
Phobos (moon) → 9,517.58 km
Apparent magnitude · 1
Phobos (moon) → 11.8
Average orbital speed · 1
Phobos (moon) → 2.138 km/s
Axial tilt · 1
Phobos (moon) → 0°
Designation · 1
Phobos (moon) → Mars I
Dimensions · 1
Phobos (moon) → 25.90 km × 22.60 km × 18.32 km (± 0.08 km × 0.08 km × 0.06 km)
Discovered by · 1
Phobos (moon) → Asaph Hall
Discovery date · 1
Phobos (moon) → 18 August 1877

Important terminology Word statistics

Use these terms to understand the vocabulary surrounding the topic, not as a checklist for keyword stuffing.

Important terminology

phobos mars surface mission deimos orbit martian space would moon stickney km could grooves mi proposed tidal return moons crater

Entity relationships Subject–Predicate–Object triples

SubjectPredicateObjectConfidenceSrc
Phobos (moon)AdjectivesPhobian /ˈfoʊbiən/1.00infobox
Phobos (moon)Albedo0.071 ± 0.012 at 0.54 μm1.00infobox
Phobos (moon)Apoapsis9,517.58 km1.00infobox
Phobos (moon)Apparent magnitude11.81.00infobox
Phobos (moon)Average orbital speed2.138 km/s1.00infobox
Phobos (moon)Axial tilt0°1.00infobox
Phobos (moon)DesignationMars I1.00infobox
Phobos (moon)Dimensions25.90 km × 22.60 km × 18.32 km (± 0.08 km × 0.08 km × 0.06 km)1.00infobox
Phobos (moon)Discovered byAsaph Hall1.00infobox
Phobos (moon)Discovery date18 August 18771.00infobox
Phobos (moon)Eccentricity0.01511.00infobox
Phobos (moon)Equatorial rotation velocity11.0 km/h (6.8 mph) (at longest axis)1.00infobox
Phobos (moon)Escape velocity11.39 m/s (41 km/h)1.00infobox
Phobos (moon)Inclination1.093° (to Mars's equator) 0.046° (to local Laplace plane) 26.04° (to the ecliptic)1.00infobox
Phobos (moon)Mass1.0638×1016 kg (3 σ)1.00infobox
Phobos (moon)Mean density1.861±0.011 g/cm31.00infobox
Phobos (moon)Mean radius11.08±0.04 km1.00infobox
Phobos (moon)Named afterΦόβος1.00infobox
Phobos (moon)Orbital period (sidereal)0.31891023 d (7 h 39 m 12 s)1.00infobox
Phobos (moon)Periapsis9,234.42 km1.00infobox
Phobos (moon)Pronunciation/ˈfoʊbɒs/ or /ˈfoʊbəs/1.00infobox
Phobos (moon)Satellite ofMars1.00infobox
Phobos (moon)Semi-major axis9,376 km (2.76 Mars radii/1.472 Earth radii)1.00infobox
Phobos (moon)Surface area1,640±8 km21.00infobox
Phobos (moon)Surface gravity0.0057 m/s2 (581.4 μ g)1.00infobox
Phobos (moon)Symbol(rare)1.00infobox
Phobos (moon)Synodic rotation periodSynchronous1.00infobox
Phobos (moon)Temperature≈ 233 K1.00infobox
Phobos (moon)Volume5,695±32 km31.00infobox

Related concept clusters Concept neighborhoods

These clusters group vocabulary that occurs around closely connected concepts in the source material.

    Connections between topic areas Semantic bridges

    Bridges can reveal useful research angles that are easy to miss in a flat list of related terms.

    Min side: 3
    For writers, content strategists, SEOs, marketers and creators — from quick topic research to advanced semantic analysis.