Quote:
Originally Posted by ATKINS
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? |
Technically, your two cases in your last paragraph say the same thing.
To answer your question tho: Partly yes, partly no. One thing to remember about both asteroids and comets is that we have gotten a close up look at very few of them. I think it is about a dozen asteroids and three or four comets have been imaged as anything more than a dot, and only one asteroid has gotten a truly close up study. When you add the changes in what we know about solar system development by finding extrasolar planets, it isnt really suprising that we find we dont know as much as we thought.
As a matter of fact, I would imagine that things will be in a state of flux for a while. New Horizions will give us our first good look at a KBO in a few years, and Dawn will give us our first good look at a couple large asteroids in a few years. With the nasty habit of most probes leading to more questions than answers, I think that our understanding of the solar system may change quite a bit.
When it comes down to it, I think that the lines between comet and asteroid will become a bit more blurred. Comets may end up being more icy asteroids than a different object. It may turn out that there was alot more mixing of the protosolar nebula than is currently believed. It may turn out that alot of comets were scattered out of the inner solar system by developing planets. I would think when all is said and done, you will have a range of objects from dirtballs (asteroids), to icy dirtballs (short-period comets), to dirty iceballs (long period comets/ KBOs).
Lastly remember that we still havent gotten a good look at a long term comet. All we have seen right now are short period comets. Being so close to the sun may have effects that havent been taklen into account yet.