Jupiter, Io, and Ganymede's Shadow . ... Credit Copyright: NASA , Voyager Explanation: Jupiter , the solar system 's largest planet, is seen here next to Io , its closest Galilean moon. On the cloud tops of Jupiter near the left edge of the picture can be seen a dark circular spot which is caused by the shadow of Jupiter 's largest moon Ganymede . Jupiter 's cloud tops show light bands and dark belts. ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ...