Ida and Dactyl: Asteroid and Moon . ... Credit Copyright: Galileo Project , JPL , NASA Explanation: This asteroid has a moon ! ... The second asteroid it photographed, Ida , was discovered to have a moon which appears as a small dot to the right of Ida in this picture . ... Dactyl is the first moon of an asteroid ever discovered. The names Ida and Dactyl are based on characters in Greek mythology . Other asteroids are now known to have moons . ... U. Based on Astronomy Picture Of the Day ...