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Fraser
2005-Jul-11, 04:01 PM
SUMMARY: When Deep Impact's impactor slammed into Comet Tempel 1 on July 4, 2005, it released a tremendous cloud of fine powdery material from the comet's nucleus. Scientists are still studying the volumes of data acquired by Deep Impact, but it appears this plume was much brighter than anyone had expected; its surface was more like talcum powder than sand. The crater was probably on the large side of what was being predicted: 50 - 250 metres (165 - 820 feet).

View full article (http://www.universetoday.com/am/publish/deep_impact_tells_story.html)

What do you think about this story? Post your comments below.

antoniseb
2005-Jul-11, 04:21 PM
This tells us just how much we needed this mission. I was skeptical at first, thinking the mission would not give us that much new and interesting information about comets, but as the day approached there were a lot of interesting ideas expressed.

At the moment, based on the Deep Impact results so far, I'm imagining short period comets like 9P/Tempel 1 as being objects that formed in the outer Solar System, composed of a mixture of ices, such as water, methane, CO2, and more complex hydrocarbons, along with fine silicate dust. Eventually some close encounter with an outer planet diverted the object toward the inner Solar System.

Once in the inner Solar System, the outer parts of this comet, end up getting the materials with lower melting points to vaporize, especially near the surface of the several mile in diameter object. Inevitably some more solid materials are jetted out with these gasses, but for the most part it is Methane at first that goes, leaving behind a fragile crunchy random lattice work perhaps several hundred meters deep that hold up the surface above the hard icy interior, and acts as an insulator for the deepest part of the interior. This lattice is something that can easily be collapsed by a collision, resulting in the deep crater walls we see in Wild 2, and other objects.

It will be interesting to see what the more serious researchers come up with as their model of the interior in the days and months ahead. In any case this is a great new view of comets, and it took a well observed collision to get it to happen. Congrats to Ahearn and his team.

VanderL
2005-Jul-11, 05:40 PM
Originally posted by antoniseb@Jul 11 2005, 04:21 PM
This tells us just how much we needed this mission. I was skeptical at first, thinking the mission would not give us that much new and interesting information about comets, but as the day approached there were a lot of interesting ideas expressed.

At the moment, based on the Deep Impact results so far, I'm imagining short period comets like 9P/Tempel 1 as being objects that formed in the outer Solar System, composed of a mixture of ices, such as water, methane, CO2, and more complex hydrocarbons, along with fine silicate dust. Eventually some close encounter with an outer planet diverted the object toward the inner Solar System.

Once in the inner Solar System, the outer parts of this comet, end up getting the materials with lower melting points to vaporize, especially near the surface of the several mile in diameter object. Inevitably some more solid materials are jetted out with these gasses, but for the most part it is Methane at first that goes, leaving behind a fragile crunchy random lattice work perhaps several hundred meters deep that hold up the surface above the hard icy interior, and acts as an insulator for the deepest part of the interior. This lattice is something that can easily be collapsed by a collision, resulting in the deep crater walls we see in Wild 2, and other objects.

It will be interesting to see what the more serious researchers come up with as their model of the interior in the days and months ahead. In any case this is a great new view of comets, and it took a well observed collision to get it to happen. Congrats to Ahearn and his team.
The data don't support your view, how do you interpret the Swift team conclusion Deep Impact hit a "hard surface" because of the UV signal? How do you account for the high increase of the amount of dust, and almost no increase in water vapour (not the OH)? How do you propose jets are formed when the surface is (as NASA claims) a deep dust layer? How do you account for the strengthening of the existing jets, and the emergence of several new jets? Remember the collision was compared to a Jumbo jet being hit by a gnat.

Cheers.

P.S. I agree with your congratulations, the achievement is outstanding.

antoniseb
2005-Jul-11, 06:09 PM
Originally posted by VanderL@Jul 11 2005, 05:40 PM
The data don't support your view, how do you interpret the Swift team conclusion Deep Impact hit a "hard surface" because of the UV signal? How do you account for the high increase of the amount of dust, and almost no increase in water vapour (not the OH)? How do you propose jets are formed when the surface is (as NASA claims) a deep dust layer? How do you account for the strengthening of the existing jets, and the emergence of several new jets?
I think it DID hit a hard surface after wizzing through a few hundred meters (maybe less) of this fragile stuff I talked about above. I thought I made that pretty clear, but I guess not. Sorry for my inarticulateness. I think the outer few hundred meters (under whatever dust or tar layer is there) has a structure like a giant house of microscopic icy cards, just waiting to fall down.

The high increase in the amount of dust? I thought that was pretty clear too, but I guess not. Some small percentage of the material in the fragile stuff was dust particles. As it got blown out into the coma, the water ice got dissociated into Hydrogen and Hydroxyl ions, leaving dust and Hydroxyl.

No Water vapour? What a surprise, Water is not stable in interplanetary space. It gets ionized very quickly.

I don't think the surface IS a deep dust layer. See above.

The creation of new jets, strengthening of old jets... I think this happened because when the probe hit the hard body of the comet a few hundred meters down it shook things, and the fragile ice layer cracked in places opening spaces for sunlight to come through and heat places that have been cold for a long time.

Bear in mind that this is how I'm envisioning it now, but certainly more evidence could come that will result in my having to give up this idea, and use a different model. Forthe moment this model seems to be working, and doesn't require having to adopt any ideas about eletrodynamic machining and arc-welding.

VanderL
2005-Jul-11, 08:51 PM
Originally posted by antoniseb@Jul 11 2005, 06:09 PM

I think it DID hit a hard surface after wizzing through a few hundred meters (maybe less) of this fragile stuff I talked about above. I thought I made that pretty clear, but I guess not. Sorry for my inarticulateness. I think the outer few hundred meters (under whatever dust or tar layer is there) has a structure like a giant house of microscopic icy cards, just waiting to fall down.


Well, sorry for this, I really couldn't tell whether you meant that there was a hard surface. But if I understand you correctly there is a thin tar-like (or dusty?) layer, then a rather deep and brittle icy layer (several hundred meters), followed by hard icy core.

This would mean that an impactor would not reach the hard surface before having plowed through the outer several hundred meters. The UV flash was immediate, so in reality it hit the hard surface first (the short early flash is discounted for the moment). This is not consistent with your description.


The high increase in the amount of dust? I thought that was pretty clear too, but I guess not. Some small percentage of the material in the fragile stuff was dust particles. As it got blown out into the coma, the water ice got dissociated into Hydrogen and Hydroxyl ions, leaving dust and Hydroxyl.

I didn't say just large amounts of dust, but a large amount of dust without large quantities of water vapour. And water vapour might not be stable, it is measurable, and the measurement shows an intial decrease followed by a marginal (if any) increase. This means there is lots of dust and almost no evidence of ice (water).


No Water vapour? What a surprise, Water is not stable in interplanetary space. It gets ionized very quickly.

It is there in measurable quantities, even before impact (thus stable enough), and it should show an increase even if it isn't stable.


I don't think the surface IS a deep dust layer. See above.

No, as you explained, but NASA thinks so, and what makes you think there is no deep dust layer? Me, I think the high relief (and UV signature) means it can't be dust.


The creation of new jets, strengthening of old jets... I think this happened because when the probe hit the hard body of the comet a few hundred meters down it shook things, and the fragile ice layer cracked in places opening spaces for sunlight to come through and heat places that have been cold for a long time.

That's completely contrary to expectations, but that's no problem, the problem is that the jets should be in one place only, the impact site, and not on the opposite side of the comet (where one of the two pre-impact jets is). Or do you suppose the impact nearly shattered the comet? I don't think the energy of the impact could have started jets miles away from the impact site, just by shaking things up.
Also, it would mean the impact crater is really, really deep and really really large.

Frustrating that the impact site isn't imaged, it shows the release of dust and light was far beyond expectations.



Bear in mind that this is how I'm envisioning it now, but certainly more evidence could come that will result in my having to give up this idea, and use a different model. Forthe moment this model seems to be working, and doesn't require having to adopt any ideas about eletrodynamic machining and arc-welding.

I know, it's early days and a lot more data will come in, and you should also take my arguments with the appropriate reserve. My concern is that NASA is releasing strange conclusions (a dust layer hundreds of meters thick) that can't be justified by the data.
I won't start turning this thread into what I think happened, that's already in the EU thread, but whatever the conclusions that can be made from the data, we must try to be objective and consistent. If the data don't support a "dirty snowball" we should be prepared to ditch the model.
NASA seems to be prepared to ditch it (as I said, several hundred meters of dust are in contradiction with the snowball model), as evidenced by the press release.
I just hope we don't get another inconsistent model in it's place.

Cheers.

antoniseb
2005-Jul-11, 09:45 PM
Originally posted by VanderL@Jul 11 2005, 08:51 PM
The UV flash was immediate, so in reality it hit the hard surface first (the short early flash is discounted for the moment). This is not consistent with your description.
Sure it is. The UV flash was from when the impactor hit the surface at 23,000 mph. The big plume started after it hit the solid surface underneath.


That's completely contrary to expectations, but that's no problem, the problem is that the jets should be in one place only, the impact site, and not on the opposite side of the comet (where one of the two pre-impact jets is). Or do you suppose the impact nearly shattered the comet?
I'm not sure it's completely contrary to expectations, but it certainly is outside the expectations. Concerning the forming of new jets, the model I'm describing would not require much of a shake of vibration to open up a new crack, and allow sunlight into volatile materials. No need to almost shatter things, just shake things a little bit.

One of my hobbies is calligraphy. Someone walking across the floor and hitting the same support beam I'm sitting over can make a visible impact on my work without almost bringing down the house.

iantresman
2005-Jul-11, 09:59 PM
"You have to think of it in the context of its environment," said Dr. Pete Schultz, Deep Impact scientist from Brown University, Providence, R.I. "This city-sized object is floating around in a vacuum.
A vacuum!... this is the same vacuum that knocked out Apollo 13, and which astronauts have to wear protective clothing, and I haven't even mentioned the plasma universe folk.

No wonder some of us are at odds with the standard view.

Regards,
Ian Tresman

Guest
2005-Jul-12, 07:23 AM
Originally posted by antoniseb+Jul 11 2005, 09:45 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (antoniseb @ Jul 11 2005, 09:45 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-VanderL@Jul 11 2005, 08:51 PM
The UV flash was immediate, so in reality it hit the hard surface first (the short early flash is discounted for the moment). This is not consistent with your description.
Sure it is. The UV flash was from when the impactor hit the surface at 23,000 mph. The big plume started after it hit the solid surface underneath.

[/b][/quote]
No, this isn&#39;t consistent. UV indicates hard surface, so the hard surface is on top, not underneath. You described the surface as a tar-like layer on top of a deep brittle layer, that&#39;s what I would call a soft surface.




That&#39;s completely contrary to expectations, but that&#39;s no problem, the problem is that the jets should be in one place only, the impact site, and not on the opposite side of the comet (where one of the two pre-impact jets is). Or do you suppose the impact nearly shattered the comet?
I&#39;m not sure it&#39;s completely contrary to expectations, but it certainly is outside the expectations. Concerning the forming of new jets, the model I&#39;m describing would not require much of a shake of vibration to open up a new crack, and allow sunlight into volatile materials. No need to almost shatter things, just shake things a little bit.

One of my hobbies is calligraphy. Someone walking across the floor and hitting the same support beam I&#39;m sitting over can make a visible impact on my work without almost bringing down the house.

But your model requires a lot of assumptions: a solid icy surface underneath 2 other hypothetical layers, the probe penetrating all these layers, a large amount of ice, and the generation of new jets by making cracks far away from the impact site, and these cracks need to be very deep and stable, plus let sunlight in. Logic aside, the simplest model seems the best to start with. I&#39;m sure you agree this is stretching it a bit.


Cheers.

antoniseb
2005-Jul-12, 12:10 PM
Originally posted by Guest@Jul 12 2005, 07:23 AM
UV indicates hard surface, so the hard surface is on top, not underneath. You described the surface as a tar-like layer on top of a deep brittle layer, that&#39;s what I would call a soft surface.
Suppose that tar surface is similar to an asphault road bed. That would be hard enough for some UV flash. Keep in mind that the initial UV flash was not all that bright.

But your model requires a lot of assumptions: a solid icy surface underneath 2 other hypothetical layers, the probe penetrating all these layers, a large amount of ice, and the generation of new jets by making cracks far away from the impact site, and these cracks need to be very deep and stable, plus let sunlight in.

Maybe there is a simpler model. This is the one I&#39;m working with, and it makes sense to me from the perspective of what the mainstream view of the origin and operation of comets is. That is they formed out near shere Jupiter and Saturn are and were ejected into the outer Solar System before the Sun got really hot, and they returned one (or a few) at a time. As they heat up in their tours of the inner Solar System there is differential vaporizing of the various ices they are made of, leaving behind a crystaline-sponge-like surface that could be quite deep. This model does NOT require any undetectable electrons, or strange arrangement of charge in the Solar System, or new physics of any kind. I think that the arrangement I&#39;m describing may be a little complicated, but it is a natural arrangement.

VanderL
2005-Jul-12, 01:39 PM
Originally posted by antoniseb+Jul 12 2005, 12:10 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (antoniseb &#064; Jul 12 2005, 12:10 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-Guest@Jul 12 2005, 07:23 AM
UV indicates hard surface, so the hard surface is on top, not underneath. You described the surface as a tar-like layer on top of a deep brittle layer, that&#39;s what I would call a soft surface.
Suppose that tar surface is similar to an asphault road bed. That would be hard enough for some UV flash. Keep in mind that the initial UV flash was not all that bright.[/b][/quote]

The first flash was short (not less bright), appr. 50 msec, then nothing for 100 msec, and then the second flash. Both flashes were UV flashes, and if we have layer of asphalt on a comet, how do you suppose the ice becomes heated to form jets anyway?




But your model requires a lot of assumptions: a solid icy surface underneath 2 other hypothetical layers, the probe penetrating all these layers, a large amount of ice, and the generation of new jets by making cracks far away from the impact site, and these cracks need to be very deep and stable, plus let sunlight in.

Maybe there is a simpler model. This is the one I&#39;m working with, and it makes sense to me from the perspective of what the mainstream view of the origin and operation of comets is. That is they formed out near shere Jupiter and Saturn are and were ejected into the outer Solar System before the Sun got really hot, and they returned one (or a few) at a time. As they heat up in their tours of the inner Solar System there is differential vaporizing of the various ices they are made of, leaving behind a crystaline-sponge-like surface that could be quite deep. This model does NOT require any undetectable electrons, or strange arrangement of charge in the Solar System, or new physics of any kind. I think that the arrangement I&#39;m describing may be a little complicated, but it is a natural arrangement.

Could you at least acknowledge that the snowball model is in trouble?
Your "model" is complicated and is a variation on the snowball idea that jets are ice/volatile driven phenomena. Your line of reasoning might be logical to you, but is it true? What evidence supports your model?
Btw, if you want to say something about the EU model, please do it in that thread, discrediting another model doesn&#39;t make yours work.

Cheers.

antoniseb
2005-Jul-12, 02:45 PM
Originally posted by VanderL@Jul 12 2005, 01:39 PM
if you want to say something about the EU model, please do it in that thread, discrediting another model doesn&#39;t make yours work.
Yes, I will confine my EU comments to the EU thread, however in this thread, YOU described my explanation as MORE complicated than some other model. I wanted to make clear that my model required fewer extraordinary assumtions than did the other model I supposed you were talking about.


Could you at least acknowledge that the snowball model is in trouble?

No, I don&#39;t think it is in trouble. The model I described to you is essentially a dirty snowball which has been modified by continual heating. Prior to Deep Impact there hadn&#39;t been much attention to how the interior of such an object would evolve. We will get a much better idea when Rosetta lands in 2014 on 67P/Churyumov-Gerasimenko. For now, what I&#39;m suggesting to you seems consistent with what we&#39;ve observed about comets.

Your "model" is complicated and is a variation on the snowball idea that jets are ice/volatile driven phenomena.
I said above that my "model" is an attempt at describing a natural situation. If I tried to describe the operation of the human cells in your body, you&#39;d have to say that my model was complicated. Nature is complicated. I&#39;ll grant that I can also describe a complicated model that is completely wrong, but eventually some test will show that it is wrong. The "dirty snowball" was a simple model. Now we have more data that tells us something (not well defined yet) about the structure and makeup of this dirty snowball. The phenomena we saw pretty much demand that there are different layers. I think the ones I described are still somewhat over-simplified for a natural system, but that is for lack of additional defining data. I reject the idea that imposing detail from new data makes it "too complicated" to be correct.

Your line of reasoning might be logical to you, but is it true?
For the record, I have said repeatedly that the model I&#39;m suggesting is based on preliminary data, and I do not make claims that it is the absolute truth. I have said only that it explains what we saw. I fully expect to have to modify the suggestion as more details become available, and perhpas toss it out completely in 2014.

VanderL
2005-Jul-12, 05:26 PM
Originally posted by antoniseb+Jul 12 2005, 02:45 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (antoniseb &#064; Jul 12 2005, 02:45 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-VanderL@Jul 12 2005, 01:39 PM
if you want to say something about the EU model, please do it in that thread, discrediting another model doesn&#39;t make yours work.
Yes, I will confine my EU comments to the EU thread, however in this thread, YOU described my explanation as MORE complicated than some other model. I wanted to make clear that my model required fewer extraordinary assumtions than did the other model I supposed you were talking about.
[/b][/quote]
No, I reserve the EU comments to that thread, and so should you. Never in this thread was I comparing your model with the EU model, I was pointing to what I see as evidence that the "dirty snowball" model (and yours) is incompatible with the new data from the Deep Impact mission.


QUOTE
Could you at least acknowledge that the snowball model is in trouble?

No, I don&#39;t think it is in trouble. The model I described to you is essentially a dirty snowball which has been modified by continual heating. Prior to Deep Impact there hadn&#39;t been much attention to how the interior of such an object would evolve. We will get a much better idea when Rosetta lands in 2014 on 67P/Churyumov-Gerasimenko. For now, what I&#39;m suggesting to you seems consistent with what we&#39;ve observed about comets.


As I said the data are incompatible with the current model. I haven&#39;t seen any arguments to think otherwise. Why isn&#39;t the model in trouble?
I don&#39;t think Rosetta will provide us with more detail about a comet&#39;s interior, for now the exterior is difficult enough.


I said above that my "model" is an attempt at describing a natural situation.
You also didn&#39;t answer some of my questions:
What evidence supports your model?
How do you suppose jets are formed when the outer layer is like "asphalt".


If I tried to describe the operation of the human cells in your body, you&#39;d have to say that my model was complicated. Nature is complicated. I&#39;ll grant that I can also describe a complicated model that is completely wrong, but eventually some test will show that it is wrong.

What makes you think that the current test did not invalidate the "dirty snowball" model?


The "dirty snowball" was a simple model. Now we have more data that tells us something (not well defined yet) about the structure and makeup of this dirty snowball.

Sure, if you ignore some of the data, it is a perfect match with the current model.


The phenomena we saw pretty much demand that there are different layers.

That&#39;s just your interpretation, I remember a more or less identical exchage after comet Wild 2 showed the same puzzling results. Too much dust and too little "volatiles".


I think the ones I described are still somewhat over-simplified for a natural system, but that is for lack of additional defining data. I reject the idea that imposing detail from new data makes it "too complicated" to be correct.

The problem is that the ideas on what happened to a comet in the past and how a comet produces jets are all assumptions that haven&#39;t been proven. And now this mission shows us that those assumption were wrong.



QUOTE
Your line of reasoning might be logical to you, but is it true?

For the record, I have said repeatedly that the model I&#39;m suggesting is based on preliminary data, and I do not make claims that it is the absolute truth. I have said only that it explains what we saw. I fully expect to have to modify the suggestion as more details become available, and perhpas toss it out completely in 2014.

No, it doesn&#39;t explain what we saw, it is your take on the DI mission, and I&#39;m questioning the validity, and also for the record, it will take several more missions to get a complete picture.

Cheers.

VanderL
2005-Jul-12, 06:46 PM
Here (http://spaceflightnow.com/deepimpact/050711swas.html) is another confirmation of the lack of water from the impact. It is quite simple really, the data don&#39;t fit the model and now everyone scrambles to try to rescue the model. I&#39;m in a cynical mood, so what I say next is hopefully wrong:
Expect the following sequence, first they&#39;ll claim there is something wrong with the data, then they need more data, next they&#39;ll claim they already suspected this outcome because of findings at previous comets, next they&#39;ll have to come up with something new, and very likely they will change the model into something that can&#39;t be verified yet, it needs a new mission. Meanwhile everything stays as it was. All these things can be happening at the same time.

To quote from the Spaceflight now article:

SWAS operators were puzzled by the lack of increased water vapor from Tempel 1. Post-impact measurements showed the comet was releasing only about 550 pounds of water per second - an emission rate very similar to pre-impact values, and less than seen by SWAS during natural outbursts in the weeks before the impact.

SMA measurements corroborate the SWAS findings. Although the SMA wasn&#39;t tuned to frequencies of water emission, which are difficult to observe from the ground due to atmospheric water vapor, it watched for other chemicals such as hydrogen cyanide. SMA astronomers saw little increase in production of gases following the impact. Gas production rates remained so low that they could set only an upper limit on the total.

"All we needed was a factor of three boost from the impact to get a definite detection," said Qi. "We didn&#39;t see that."

Qi added that the comet might become more active over the following days and weeks. "We&#39;re still hoping for a big outgassing from the new active area created by Deep Impact. If we see any signs of that, we&#39;ll make more observations."

Cheers.

antoniseb
2005-Jul-12, 07:18 PM
Hi VanderL,

Thanks for the pointer to the SpaceFlightNow article. It had some things in it I hadn&#39;t seen before.

At this point I am interested in seeing a detailed timeline of the collision, and the various observations that were made, including images. One of the things which is difficult here is the lack of scales on most graphs and images.

Another thing that is a problem for working out a good model for what we saw is not seeing a coordinated statement of the timing of various events. For example, I really only have anything about the timing of the UV flash(es) from a group of alternative theorists... nothing from the official sources.

Here are tow things of note from the article:

Modern astronomers often refer to comets as "icy dirtballs" instead, reflecting the prevailing view that comets contain more dust and less ice than previously believed.


"The big picture will emerge once astronomers meld data from different observatories at different wavelengths," said Melnick.

I agree now that the data is not supporting my house-of-cards ice model for the crust.

VanderL
2005-Jul-12, 09:49 PM
I agree now that the data is not supporting my house-of-cards ice model for the crust.


Thanks Antoniseb,

I really appreciate your honesty.


At this point I am interested in seeing a detailed timeline of the collision, and the various observations that were made, including images. One of the things which is difficult here is the lack of scales on most graphs and images.

Another thing that is a problem for working out a good model for what we saw is not seeing a coordinated statement of the timing of various events. For example, I really only have anything about the timing of the UV flash(es) from a group of alternative theorists... nothing from the official sources

Yes, we all face the same problems in not having enough and precise data. But that&#39;s really to be expected at this point. I&#39;m worried that at a later date we won&#39;t be able to actually see the data themselves, only interpretations. Anyway, the data thusfar are really indicating trouble for the "dirty whatever" model, what I&#39;m waiting for is spectral data on ions in the plasma tail, Gamma-rays, if any, and the timing of the flashes was explained by Schultz, I&#39;ll try to find the link to this information.

First and foremost however, is the absence of an increase in water vapour, and the absence of "volatiles" (I really don&#39;t know which molecules they were expecting), it shows very clearly that jets (which were produced instantly) are NOT the consequence of outgassing. This is a major finding and whatever model we end up with, it has to explain how this works. We need to review all previous comet "probings" to get the correct mechanism.



Thanks for the pointer to the SpaceFlightNow article. It had some things in it I hadn&#39;t seen before.

Now you mention it, apparently this information was released on friday July 8th, I found it today, but I have been scouring all places on the web for this kind of info, I&#39;m a bit curious how this can be "lying around" for 4 days. The SpaceFlightNow site is something I check very regularly, and I almost missed it.

Your quote about the "icy dirtballs" implies some people were already prepared to change their tack, it&#39;s almost as if they say "we knew that&#33;". Let&#39;s see what they come up with.

Cheers.

wstevenbrown
2005-Jul-12, 10:06 PM
And on all sides, the views expressed are so monolithic. Like describing bread as flour + water + trace elements.

I expect comets to show at least as much variety as meteorites-- stony, iron-nickel, carbonaceous, all-mixed-up. For comets read watery,dusty, PAH-rich, neon-rich, etc.

Our experience with comets can be counted on the finger of one hand. S

aeolus
2005-Jul-12, 10:18 PM
Originally posted by wstevenbrown@Jul 12 2005, 10:06 PM
And on all sides, the views expressed are so monolithic. Like describing bread as flour + water + trace elements.

I expect comets to show at least as much variety as meteorites-- stony, iron-nickel, carbonaceous, all-mixed-up. For comets read watery,dusty, PAH-rich, neon-rich, etc.

Our experience with comets can be counted on the finger of one hand. S
True true. Good point. Lets not put too much stock in DI&#39;s findings. Not to say it isn&#39;t valuable data, of course, but it is only one comet in the end.

VanderL
2005-Jul-12, 10:28 PM
Originally posted by wstevenbrown@Jul 12 2005, 10:06 PM
And on all sides, the views expressed are so monolithic. Like describing bread as flour + water + trace elements.

I expect comets to show at least as much variety as meteorites-- stony, iron-nickel, carbonaceous, all-mixed-up. For comets read watery,dusty, PAH-rich, neon-rich, etc.

Our experience with comets can be counted on the finger of one hand. S
True, but you have to explain how they form their jets, tails.

Cheers.

VanderL
2005-Jul-12, 10:32 PM
Originally posted by aeolus+Jul 12 2005, 10:18 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (aeolus @ Jul 12 2005, 10:18 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-wstevenbrown@Jul 12 2005, 10:06 PM
And on all sides, the views expressed are so monolithic. Like describing bread as flour + water + trace elements.

I expect comets to show at least as much variety as meteorites-- stony, iron-nickel, carbonaceous, all-mixed-up. For comets read watery,dusty, PAH-rich, neon-rich, etc.

Our experience with comets can be counted on the finger of one hand. S
True true. Good point. Lets not put too much stock in DI&#39;s findings. Not to say it isn&#39;t valuable data, of course, but it is only one comet in the end. [/b][/quote]
No, no, we just have to look again at all the previous data (Wild 2, Borrelly, Halley, Hyutake, Linear, Showmaker-Levy9), we actually probed comets better than some other stuff, like the dark side of the moon. We should learn lessons from this mission.

Cheers.

Nick4
2005-Jul-27, 03:19 AM
Did they get dust from the comet after impacter hit?