One moment in an ancient, orbital dance is caught in this color picture taken by NASA Cassini spacecraft on Dec. 7, 2000, just as two of Jupiter four major moons, Europa and Callisto, were nearly perfectly aligned with each other.
One moment in an ancient, orbital dance is caught in this color picture taken by NASA Cassini spacecraft on Dec. 7, 2000, just as two of Jupiter four major moons, Europa and Callisto, were nearly perfectly aligned with each other.