by a distance of , moving in a prograde orbit. Dactyl is heavily cratered, like Ida, and consists of similar materials. Its origin is uncertain, but evidence from the flyby suggests that it originated as a fragment of the Koronis parent body. Discovery Dactyl was found on 17 February 1994 by Galileo mission member Ann Harch, while examining delayed image downloads from the spacecraft. Galileo recorded 47 images of Dactyl over an observation period of 5.5 hours in August 1993. The spacecraft was from Ida and from Dactyl when the first image of the moon was captured, 14 minutes before Galileo made its closest approach. Dactyl was initially designated 1993 (243) 1. It was named by the International Astronomical Union in 1994, for the mythological dactyls who inhabited Mount Ida on the island of Crete. Physical characteristics Dactyl is an "egg-shaped" but "remarkably spherical" object measuring . It is oriented with its longest axis pointing towards Ida. Like Ida, Dactyl's surface exhibits saturation cratering. It is marked by more than a dozen craters with a diameter greater than , indicating that the moon has suffered many collisions during its history. At least six craters form a linear chain, suggesting that it was caused by locally produced debris, possibly ejected from Ida. Dactyl's craters may contain central peaks, unlike those found on Ida. These features, and Dactyl's spheroidal shape, imply that the moon is gravitationally controlled despite its small size. Like Ida, its average temperature is about . Dactyl shares many characteristics with Ida. Their albedos and reflection spectra are very similar. The small differences indicate that the space weathering process is less active on Dactyl. Its small size would make the formation of significant amounts of regolith impossible. This contrasts with Ida, which is covered by a deep layer of regolith. The two largest imaged craters on Dactyl were named Acmon and Celmis , after two of the mythological dactyls. Acmon is the largest crater in the above image, and Celmis is near the bottom of the image, mostly obscured in shadow. The craters are 300 and 200 meters in diameter, respectively. Orbit Dactyl's orbit around Ida is not precisely known. Galileo was in the plane of Dactyl's orbit when most of the images were taken, which made determining its exact orbit difficult. Dactyl orbits in the prograde direction and is inclined about 8° to Ida's equator. Based on computer