 The Galileo images also led to the discovery that space weathering was taking place on Ida , a process which causes older regions to become more red in color over time . The same process affects both Ida and its moon , although Dactyl shows a lesser change . The weathering of Ida 's surface revealed another detail about its composition : the reflection spectra of freshly exposed parts of the surface resembled that of OC meteorites , but the older regions matched the spectra of S @-@ type asteroids . 
