Metis (moon)

Metis or Jupiter XVI, is Jupiter's closest moon.

Metis

Image of Metis was taken by Galileo's solid state imaging system between November 1996 and June 1997.
Discovery
Discovered by	S. Synnott
Discovery date	March 4, 1979
Orbital characteristics
Periapsis	127,974 km
Apoapsis	128,026 km
Mean orbit radius	128,000 km (1.792 RJ)
Eccentricity	0.0002
Orbital period	0.294780 d (7 h 4.5 min)
Average orbital speed	31.501 km/s
Inclination	0.06° (to Jupiter's equator)
Satellite of	Jupiter
Physical characteristics
Mean radius	21.5 ± 2.0 km
Volume	~42,700 km³
Mass	3.6 ×1016 kg
Mean density	0.86 g/cm³ (assumed)
Surface gravity	0.005 m/s² (0.0005 g)
Escape velocity	0.012 km/s
Rotation period	synchronous
Axial tilt	zero
Albedo	0.061 ± 0.003
Temperature	~123 K

Metis was found in 1979 by Stephen P. Synnott in images taken by the Voyager 1 probe. Its designation was S/1979 J 3. In 1983 it was named after the mythological Metis, a Titaness who was the first wife of Zeus (the Greek equivalent of Jupiter).

Metis is not a sphere and measures 60×40×34 km across. The composition and mass of Metis are not known, but assuming that its mean density is like that of Amalthea (~0.86 g/cm³), its mass can be estimated as ~7×10¹⁶ kg. Amalthea's density implies that moon is composed of water ice with a porosity of 10-15%, and Adrastea may be similar.

The surface of Metis is very cratered. It is dark and appears to be reddish in color.

Orbit

Metis is the closest moon to Jupiter. It orbits Jupiter at a distance of ~128,000 km. It has a very small orbital eccentricity (~0.0002) and inclination (~ 0.06°) relative to the equator of Jupiter.7

Exploration

The images taken by Voyager 1 showed Metis only as a dot, and very little was known about Metis until the arrival of the Galileo spacecraft. Galileo took pictures of almost all of the surface of Metis and put constraints on its composition.

Other websites

• Metis Profile Archived 2007-11-09 at the Wayback Machine by NASA's Solar System Exploration