Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

July 11, 1996

Ganymede: A Really Groovy Moon
Credit: Galileo Mission Team, Galileo Spacecraft, NASA

Explanation: Ganymede's surface is a wrinkled mess. As large ice-sheets shift on the moon's surface, parts of the surface buckle causing high ridges, deep furrows, and parallel grooves. This photo, taken by the Galileo spacecraft currently orbiting Jupiter, was released yesterday. The large circular feature near the picture bottom is a large impact crater. The impact that caused this large crater also caused the strange dark ejecta seen to the crater's right. The Sun illuminates the scene from the lower left. The Galileo spacecraft has also just discovered that Ganymede has a region of orbiting charged particles called a magnetosphere - a first for any moon. How Ganymede is able to generate a magnetosphere is a mystery.

APOD's Archive of Galileo at Ganymede
Tomorrow's picture: Ancient Cratered Plains on Ganymede

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
&: Michigan Tech. U.