text: what is the difference between comets and asteriods?   comets are, in the phrasing of astronomer fred c. whipple, "dirty snowballs", that is, they are made of ices (co2, h2o, frozen nh3 and ch4) with a mixture of various carbons and silicates to make a lump.  most comets travel in extremely elongated orbit, and spend most of their time far from the sun (if they din't, the ices would evaporate, and you are left with a meteor shower). asteroids are chunks of rock and metallic material that can be nickel-iron (about 20%), silicate (about half), a mix of nickel iron and silicate (20%) or carbonaceous material (10%).  while the majority of asteroids are found between mars and jupiter, there are many known that fall outside those limits.  some asteroids are known to have their own very small moons.