Comets and Asteroids
Debris from formation of Solar System.
Asteroids: lumps of rock a few km in size
- Most in belt between Mars & Jupiter.
Comets: dirty snowballs of ices and rocks
- Primordial, but transient,
- Highly elliptical orbits, from Kuiper Belt (50-500AU) or Oort Cloud (to 50,000AU),
- Tails only when near Sun (vaporised ice), blown out by the solar wind & sunlight.