I've only just noticed
this article (published about a month ago) on recent research results from the "Stardust" mission obtained by scientists at the Lawrence Livermore National Laboratory (a US Govt funded laboratory). They claim, in essence, that “as a whole, the samples look more asteroidal than cometary”, that "the Stardust material resembles chondritic meteorites from the asteroid belt", and that "the dust from Wild 2 also is missing ingredients that would be expected in comet dust". Their findings were published in the 25 January 2008 issue of "Science". This is the
abstract (I don't have access to the full article).
In a related article in the same issue, Richard A. Kerr writes under the title "Where Has All the Stardust Gone?" that "On page 447 of this issue of Science, researchers report that they have failed to find a single speck of the unaltered, so-called presolar material thought to abound in icy comets in the dust sample that the Stardust spacecraft returned from comet Wild 2 in January 2006."
Do these latest findings not provide further evidence that the current mainstream "dirty iceball" or "icy mudball" model of comet formation in the Kuiper belt has been falsified and that comets are simply asteroids which display cometary behaviour in certain situations?