Phobos
Spiralling into Mars, and probably a rubble pile rather than solid rock.
Where it is right now
Phobos is in Taurus, 1.99 AU away.
Computed for 2 August 2026, 17:00 UTC, and recomputed at least hourly. This page is cached, so treat the line above as accurate to the hour rather than to the second. The map shows the live position.
Position from a Kepler propagation of the published elements below, accurate to about an arcminute.
Facts
Every line carries the source it came from.
- Mean radius
- 11.1 kmSource: NASA/JPL Planetary Satellite Physical Parameters
- Orbits
- Mars, 9,375 km out on averageSource: NASA/JPL Planetary Satellite Mean Elements
- Orbital period
- 0.32 daysSource: NASA/JPL Planetary Satellite Mean Elements
- Orbit shape
- eccentricity 0.0150, inclined 1.10 degrees to Mars's Laplace planeSource: NASA/JPL Planetary Satellite Mean Elements
- Discovered
- 1877 by A. HallSource: NASA/JPL Planetary Satellite Discovery Circumstances
Physical size
- Mean radius
- 11.1 km
- Diameter
- 22 km across
Orbit
Elements are relative to Mars.
- Average distance from Mars
- 9,375 km
- Closest and furthest
- 9,234 km to 9,516 km
- Eccentricity
- 0.0150, almost circular
- Inclination to Mars's reference plane
- 26.05 degrees
- Orbital period
- 7.6 hours
- Longitude of ascending node
- 84.91 degrees
- Argument of periapsis
- 342.86 degrees
- Mean anomaly at J2000.0
- 189.70 degrees
Family
Orbits Mars.
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Catalog id phobos. 3,172 objects on the map, of which 171 are hand-authored with sourced facts.