Comets - Not What We Expected

[MeteorWayne]

Just a brief comment.

So far we have seen 4 comet nuclei close up (IIRC). All have shown that most of the surface is inactive with a rocky or possible organic goo layer covering > 90% of the surface. The emissions that create the coma come from very limited areas on the surface. Therefore I don't understand why it should be terribly surprising that the ONE experiment we have conducted, impacting an object into a cometary surface, excavated an area that had little or no ice.

9P/ Tempel 1 is not a particulary active comet (certainly much less so than Halley, or Hale-Bopp) so it would be expected that it's active areas would be even smaller.

The icy content of comets is beyond dispute, considering the spectral measurements showing numerous ice decay by products in the coma of every comet that has been examined in such a way...dozens of them by the way, since a close up is not needed for that.

MW

 

[MeteorWayne]

Comet 1P/Halley

Borelly, normal exposure:

Borelly overexposed to bring out faint dust and gas emissions:

Comet Wild 2 at normal exposure. See any ice or dust being driven off?

Wild 2 with coma vastly overexposed to show faint dust and gas emission.

 

[yevaud]

Michael, the threads I have been able to (so far) locate are as follows:

Deep Impact Predictions: http://www.space.com/common/forums/viewtopic.php?f=12&t=6504&hilit=deep+impact+predictions

Continuum Between Asteroids and Comets: http://www.space.com/common/forums/viewtopic.php?f=12&t=5132&hilit=deep+impact+predictions

Ice on Comet Tempel 1: http://www.space.com/common/forums/viewtopic.php?f=12&t=6450&start=0&hilit=deep+impact+predictions

Where's the Discussion on Stardust Data: http://www.space.com/common/forums/viewtopic.php?f=12&t=6339&hilit=deep+impact+predictions

Please note that some of these debates were very heated and rancorous. Yet, all involved covered a great deal of territory on this subject.

 

[MeteorWayne]

Unfortunately, we really are into been there done that territory.

The impact was almost 4 years ago, and the papers came out between 2 and 3 years ago.

Unless you have unlimited time to spare, like a YouTube EPH woo woo, it takes time to dig up the journal articles.

Besides, much of the real science is in Nature or Science, which you have to subscribe to to read in full. I can tell you what they say, but most would probably rather believe you tube, than someone actually reading the scientific facts from the actual articles.

 

[MeteorWayne]

Regarding Deep Impact:

A total of 250 million kilograms (551 million pounds) of water[35] and between 10 and 25 million kilograms (22 and 55 million pounds) of dust were lost from the impact.

(Not Peer Reviewed) http://www.newscientist.com/article/dn7961

(Not Peer Reviewed) http://news.bbc.co.uk/2/hi/science/nature/4871934.stm

That seems to disagree substantially from the YouTube statements!

 

[Michael_S]

Thanks Wayne, what I'm looking for though are the papers.

The NASA web sites only propose postulates with no supporting reviewed papers.

As for the icy structure of comets not being in debate, I have to wonder how this could be so since I've never seen a paper describing how photolysis could occur at such incredibile rates for sub-surface water ice that's not in direct contact with sunlight.

When we look at the spectrum of comets we don't see water, we see OH radicals, which is a huge difference.

I assume you know that already, I'm just restating it for the rest of the forumites.

 

[yevaud]

Well, I did locate an abstract on the problem...dated 1976. I'd presume there has been much more since.

Elsevier (Science Direct): http://www.sciencedirect.com/scienc...serid=10&md5=6ca959eedc3ce60464f07b3586391b05

Edit: and here's a full paper located at iop: http://www.iop.org/EJ/article/0004-...quest-id=3c5e0fc9-bd64-40c4-a855-feb950dce972

 

[MeteorWayne]

Thanks Wayne, what I'm looking for though are the papers.

The NASA web sites only propose postulates with no supporting reviewed papers.

As for the icy structure of comets not being in debate, I have to wonder how this could be so since I've never seen a paper describing how photolysis could occur at such incredibile rates for sub-surface water ice that's not in direct contact with sunlight.

When we look at the spectrum of comets we don't see water, we see OH radicals, which is a huge difference.

I assume you know that already, I'm just restating it for the rest of the forumites.

As I said, unless you subscribe to Nature or Science, the full papers are not available online.

When I have time I will find the issue numbers so you can try and find them at a local library.

 

[tanstaafl76]

Michael S reminds me an awful lot of Michael M.