What exactly is the difference between comets and asteroids? All the photos I've seen of both appear to be images of well-defined rocky bodies in sharp relief. However, doesn'tthis contradict theories of comets being dirty snowballs, icy dust balls, etc.

Also, why do coments break up in the OUTER solar system where there is little to NO heat intensity being received from the sun? This seems to contradict the dirty snowball theory of breakup due to sublimation as they pass by the sun?
Comet West broke up some 30 million miles or more away from the sun. Comet Linear broke up around 100 million miles from the sun. Schwassmann-Wachmann 3 began displaying a coma at 100-150 million miles from the sun, WAY to far away to be sublimating and outgassing (rather, according to traditional theory, at that distance it should be a solid block of ice undergoing ostensibly NO active processes), and subsequently broke up violently (again, around 100-150 million miles from the sun). This makes no sense from a sublimation point of view.

And why is it that some comets pass right through the interior of the solar system relatively NEAR the sun, and don't eithre break up ro completely sublimate. Considering how much more energy they're getting per second, minute or day in the innermost reaches of the solar system versus how much energy they receive at the outer portions of the solar system, one would generally expect them to either break up into a ton of pieces, or to sublimate all their "icy makeup" away and simply disappear off our sensors. But some "comets" appear to just sail right on through the inner solar system with no issues, despite apparently similar composition and size with other comets that do violently break up... This seems contradictory, especially when paired with the prior observations...
http://antwrp.gsfc.nasa.gov/apod/ap040419.html

Also, why is it that comets' comas appear to be tightly filamented overmillions of miles of space, despite gasses' proclivities to expand in 3 dimensions in a vacuum (ideal gas laws, I think they are)? What would cause these gasses to stay filamentary over such stellar distances?
http://antwrp.gsfc.nasa.gov/apod/ap040512.html

Also, why is it that when we observe comets' comas, we also observe high energy x-ray emissions coming off them? Gas sublimation should not be hot enough or violent enough an event to create x-ray emissions... What else causes x-rays (electrical arcing is a common natural source of x-rays in the lab on earth)?

Why is it that comets that come close to the sun, when imaged, still look like sharply defined rocky bodies rather than sublimating/melting/rounded icy bodies?
http://antwrp.gsfc.nasa.gov/apod/ap050915.html
http://antwrp.gsfc.nasa.gov/apod/ap060212.html

Am I confused, or is current theory? Frankly, I think current theory has so many holes in it... Now, if we let go of the theory that electricity can't flow in space... And view the comet's coma as a magnetically confined plasma filment (or several thereof), what dos that imply? Certainly SEEMS like a better explanation of why comas are confined filaments over millions of miles than the competing theory of magical ideal gases in a vacuum that don't behave as they're supposed to by dissipating a big unconfined cloud...

Consider the pot stirred. Talk amongst yourselves... Should be an interestign conversation... =o]