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.

2000 March 7 Zal Patera on Jupiter's Moon Io Credit: Galileo Project, SSI, University of Arizona, JPL, NASA

Explanation: The Galileo orbiter's flyby of Io last November captured an unusual part of Jupiter's volcanic moon. From 26,000 kilometres away, Zal Patera was found to be a cauldron of flowing lava, gaseous vents, and tremendous peaks. Red lava can be seen in the above picture erupting along the base of the volcanic caldera, while cooling black lava lines the edge of a volcanic plateau. Shadow lengths indicate that the top of Zal Patera towers nearly 5 kilometres over Io's molten surface. Galileo zoomed past Io again last month, and has begun beaming back images taken only 200 kilometres over Io's surface.