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.

November 10, 1997
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

Dark Volcano Active on Io
Credit: Galileo Project, JPL, NASA

Explanation: The surface of Io is changing even as we watch. The inset frame of Jupiter's most active moon was taken by the robot spacecraft Galileo in April. Just last month the larger image was taken. The new large black spot reveals that a volcano named Pillan Patera has been erupting during the interim. A vast moonscape roughly the size of Arizona has just been covered by some dark material. What is this material? It's composition remains unknown although it is certainly different in color from the red material seen surrounding volcano Pele on the upper left.

Tomorrow's picture: The Annotated Galactic Center

< Archive | Index | Search | Calendar | Glossary | Education | About APOD >

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.