Despite observations made in the 1990s by the Galileo spacecraft, very little is known about the moon's physical characteristics other than its size and the fact that it is tidally locked to Jupiter.

Adrastea was discovered by David C. Jewitt and G. Edward Danielson in Voyager 2 probe photographs taken on July 8, 1979, and received the designation S/1979 J 1.

Soon after its discovery, two other of the inner moons of Jupiter (Thebe and Metis) were observed in the images taken a few months earlier by Voyager 1.

Amalthea's density implies that the moon is composed of water ice with a porosity of 10–15%, and Adrastea may be similar.

[4] Due to tidal locking, Adrastea rotates synchronously with its orbital period, keeping one face always looking toward the planet.

This appears to consist primarily of material that is ejected from the surfaces of Jupiter's four small inner satellites by meteorite impacts.

[12] The exact extent of visible ring material depends on the phase angle of the images: in forward-scattered light Adrastea is firmly outside the main ring,[12] but in back-scattered light (which reveals much bigger particles) there appears to also be a narrow ringlet outside Adrastea's orbit.