Amalthea
Moon· orbits Jupiter
Amalthea is a small, irregular, reddish inner moon of Jupiter — a porous, low-density body that appears to be a loosely bound rubble pile, reddened by sulfur from Io.
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Key facts
Mass
2.08 × 10¹⁸ kg
0.0000283 Moon masses
Radius
83.5 km
5% of our Moon's radius
Surface gravity
0.0199 m/s²
0% of Earth's
Day length
12.00 hours
Orbit around Jupiter
12.0 hours
0.50 Earth days
Science
Physical
- Mass
- 2.08 × 10¹⁸ kg · 0.0000283 Moon masses
- Radius
- 83.5 km · 5% of our Moon's radius
- Density
- 853 kg/m³ · 0.85× water
- Surface gravity
- 0.0199 m/s² · 0% of Earth's
- Escape velocity
- 57.7 m/s · 1% of Earth's
Orbit around Jupiter
- Distance from Jupiter
- 1,433,405 km
- Orbital period
- 12.00 hours
- Eccentricity
- 0.003
- Inclination
- 0.40 °
Rotation
- Rotation period
- 12.00 hours
- Tidal locking
- Tidally locked to its parent
Composition
- Bulk composition
- A porous, low-density mix of water ice and rock (a likely rubble pile), its surface reddened by sulfur from Io.
Radiation & temperature
- Insolation
- 0.0357 S⊕ · 4% of the sunlight Earth receives
- Geometric albedo
- 0.09
- Equilibrium temperature
- 118 K (-155 °C)
Discovery & history
- Discovered
- September 9, 1892
- By
- Edward Emerson Barnard
- Method
- Visual discovery (telescopic)
- Name
- Amalthea, the nymph (or she-goat) who nursed the infant Zeus in Greek myth.
Amalthea was the last moon in the Solar System found by direct visual observation — Edward Barnard glimpsed it at Lick Observatory in 1892, the first new Jovian moon since Galileo's four in 1610. Reddish and irregularly shaped, it is dusted with sulfur erupted from nearby Io.
Images
Images from open archives · credit shown per image