Small bodies are not geologically active
They provide “fossil” record of early solar system
Asteroids
Mostly from region between Mars and Jupiter
Left over small debris from accretion, never assembled into a large
planet
Meteorites come mostly from asteroids
Comets
“Stored” on large elliptical orbits beyond planets
Thought to be “planetesimals” from Jovian planet region, almost
ejected from solar system in its early history
Meteorites provide only samples besides Apollo
With sample in hand, can perform very detailed analysis:
detailed chemistry; radioisotope age; other isotope info