Space · Moons

Adrastea

A moon of Jupiter — The second-innermost Jovian moon — orbits just outside Jupiter's main ring at its outer edge.

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Quick facts

Parent planet

Jupiter

Diameter (mean)

16 km

Mass

2.0 × 10¹⁵ kg
2.7e-08 Moon masses

Mean orbital radius

129,000 km

Orbital period

0.298 Earth days

Discovery year

1979

Discoverer

David C. Jewitt (Voyager 2)

Naming origin

Greek nymph who hid Zeus from Cronus

Surface conditions

Adrastea is one of the smallest named moons of Jupiter, just 20×16×14 km, orbiting in lockstep with Metis just outside the main ring. Both Adrastea and Metis are below the rotational stability limit and would be torn apart if any larger; they survive because their internal strength holds them together against tidal stress.

Missions and observations

Every Jupiter-system mission has had an opportunity to image or characterize Adrastea. The list below is the Jupiter-system mission catalog; specific Adrastea encounters are documented in mission archives.

Mission	Year at Jupiter	Status
Pioneer 10 NASA	1973	Completed
Pioneer 11 NASA	1974	Completed
Voyager 1 NASA	1979	Completed
Voyager 2 NASA	1979	Completed
Ulysses NASA/ESA	1992	Completed
Galileo NASA	1995	Completed
Cassini-Huygens NASA/ESA/ASI	2000	Completed
New Horizons NASA	2007	Completed
Juno NASA	2016	Active
Europa Clipper NASA	2030	On the way
JUICE ESA	2031	On the way

Naming etymology

Adrastea was a nymph who, with her sister Ida, hid the infant Zeus on Crete to protect him from his child-eating father Cronus. The IAU adopted the name in 1983.

Methodology & sources

Diameter, mass, and orbital parameters from JPL Solar System Dynamics — Physical Parameters. Discovery year and discoverer from the JPL Satellite Discovery Circumstances. Naming etymology from the IAU Working Group for Planetary System Nomenclature. Stylized SVG hero composed from NASA / JPL imagery as visual reference; no photographs are reproduced.