Comets and Asteroids are constantly said by science to be formed of ice and materials from the birth of the universe (Dirty Snowball Model), as this is what the latest latest latest modified Big Bang Theory idea of comets says they are.
Previous (Comet Wild 2 Stardust Mission) and latest satellite probe missions (Comet 67P Churyumov-Gerasimenko) them has and will find out that they are dusty and rocky with very little ice for most if not all of them. This has been predicted by the Electric Universe Theory for many years.
Comets and Asteroids are the same thing, they are just on different orbits. They are not different forms of planetary bodies. The main reason they are seen as different is very likely due to the electrical difference between them and the sun. With the orbit either throwing them towards the sun where they discharge and break up under electrical stress, or, they remain in a fairly stable orbit around the sun or their host planetary body.
The Oort cloud? Another made up part of the Big Bang Theory with no evidence and very unlikely to ever be found. What happens when those supposed Oort Cloud objects have little or no ammonia, methane, and water?
Also, there is no water vapour discharging, its electrical machining and discharging that helps create those amazing, numerous, moving, reappearing jets and a tail that can glow and stretch for millions of miles across the solar system.
The results of Comets being found to be made of rock and not ice, plus there being no evidence of the Oort cloud? It will be another surprise for science but they will then do the latest modification of their theories without ever seeming to question the original theories they are based on that seem to predict nothing correctly.
Comets, Asteroids and their smaller relations of of meteors have electrically discharged into planets atmospheres and land previously - Comet Shoemaker-Levy 9 impact on Jupiter, Chelyabinsk meteor (Russia 2013) and perhaps Tunguska 1908.