Wanderingspace

The main body Ida and the smaller asteroid, or moon, named Dactyl are a part of the family of asteroids found between the orbits of Mars and Jupiter. It is thought that all of these types of asteroids were created by some cataclysmic event which blew apart a larger body, perhaps around 200 to 300 km in diameter. This event (which is theoretical) would also have taken place long after the formation of the solar system and so in celestial terms it is considered a “recent” event. That means had this event not taken place we would have had at least one more dwarf planet in our solar system than we do today.

This flyby was planned as an “extra” for the Galileo mission as they were for the most part “on the way” to its central mission to the Jupiter system. It is thought that Dactyl has a nearly identical composition to Ida and is therefore not thought to be a “captured” moon, but rather one formed somehow from itslef either from a later impact or from the destruction of the originating body.

The NEAR spacecraft was designed to visit a few asteroids with the main target being one named Eros. This probe was meant only to orbit this object closely for a year… and it did. But as the probe ran out of feul and for lack of any reason not to, the controllers decided to attempt an impromptu landing on the surface. Even though the probe had not been designed to do this (it lacked landing gear of any kind) they managed to “rest” the probe carefully upon the surface in 2001 and it continued to transmit information back to Earth for more than 2 weeks from the surface.

Image Note: The color of the asteroid itself was enhanced to match that of the close up image included in the upper right. The original full image was black and white.