UPSA Object Registry

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Phobos

Natural satellite JPL Horizons

Mass: 1.08 1e20 kg
Density: 1.9 g cm^-3
Orbital period: 0.319 d
Geometric albedo: 0.06

Also known as

2 identifiers

Horizons 401MI

Recorded parameters

8 quantities with a single published value

Parameter	Value	Unit	Uncertainty	As published	Source	Reference
Mass	1.08	1e20 kg		Mass (10^20 kg )	JPL Horizons	JPL Horizons on-line ephemeris system
Density	1.9	g cm^-3		Density (g cm^-3)	JPL Horizons	JPL Horizons on-line ephemeris system
Orbital period	0.319	d		Orbital period	JPL Horizons	JPL Horizons on-line ephemeris system
Geometric albedo	0.06			Geometric Albedo	JPL Horizons	JPL Horizons on-line ephemeris system
Eccentricity e	0.0151	e		Eccentricity, e	JPL Horizons	JPL Horizons on-line ephemeris system
Inclination i deg	1.082	deg		Inclination, i (deg)	JPL Horizons	JPL Horizons on-line ephemeris system
Rotational period	Synchronous			Rotational period	JPL Horizons	JPL Horizons on-line ephemeris system
Semi major axis a km	9.3772	km		Semi-major axis, a (km)	JPL Horizons	JPL Horizons on-line ephemeris system

Provenance

where this card came from

Archive	Read at (UTC)	Record
JPL Horizons	2026-08-14 17:08	open at source

Machine-readable: /api/v1/object/phobos · Registry entry updated 2026-08-14.