6
Are
Asteroids Primitive?
•Ida
(56 km diam.) and its moon Dactyl (1.5 km diam.)
–Colors
have been “stretched” to show subtle differences
•Imaged
by Galileo on its way out to Jupiter
•Presence of craters indicates great age
–Absolute age requires knowledge of cratering rate
– uncertain
–Not spherical – gravity too weak to pull it into a
sphere
