Deep Impact Predictions

telfrow · Sep 7, 2005

Re: Crater Size The team estimates the impact blasted away a crater about 100 metres wide and up to 30 m deep. Crucially, organic molecules were among the material ejected. Neither the full range of molecules nor their abundances have been determined yet, but researchers say they have found a surprisingly high amount of methyl cyanide, a molecule seen in large quantities in another comet. From: http://www.newscientist.com/article.ns?id=dn7961 <div class="Discussion_UserSignature"> Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild. - Tennyson </div>

exoscientist · Sep 7, 2005

Dmjspace, I think A'hearn's stated confirmation of the "snowy dirtball" hypothesis was in comparison to the original theory they were "dirty snowballs". That is, the data supports the idea there is more dirt than ice. Perhaps you should write A'hearn and other members of the Deep Impact team to ask how the data would apply to the exploded-planet-hypothesis for the origin of comets. Bob Clark <div class="Discussion_UserSignature"> </div>

centsworth_II · Sep 7, 2005

It seems to me that the large amount of dust supports the view that the comet started as a "dirty snowball". Its surface being desiccated after repeated aproaches to the sun. I cannot imagine an asteroid building up such a thick layer of dust even after millions of years of impacts. The once feared thick layers of dust on the Moon that would swallow a lander turned out not to exist. I would guess that a similar impactor hitting an asteroid would give a much different result, ejecting much less dust. <div class="Discussion_UserSignature"> </div>

dmjspace · Sep 7, 2005

Are you suggesting that I assume A'Hearn is being misquoted on everything he says that doesn't fit the standard model? These quotes are by the scientists directly involved with the mission. They say repeatedly that they are surprised. The results are unexpected. Surprising results are not good news for models that are supposed to have been fleshed out by many scientists over many decades. The scientists in your sources AND my sources are unified in saying, even at this early stage, that there is far more rock than ice to Tempel 1. Another article is out today on the Deep Impact results. It is unambiguous in its message: Composition of a Comet Poses a Puzzle for Scientists The crux of the problem, as reported by the New York Times and soon to be reported at the journal Science's web site, is that Although comets form at the frigid edges of the solar system, they appear somehow to contain minerals that form only in the presence of liquid water, and at much warmer temperatures, scientists are reporting today. This report refers to the Spitzer observations, which have been discussed at length earlier in this thread. It says, In the burst of light after the collision, Spitzer detected specific colors of infrared light that indicated that Tempel 1 contained clays and carbonates, the minerals of limestone and seashells. Clays and carbonates both require liquid water to form. Though resident EPH skeptics have assured me that this is not a problem for the dirty snowball model, scientists involved with the data are finding this a major dilemma: "How do clays and carbonates form in frozen comets where there isn't liquid water?" said Carey M. Lisse, a research scientist at the Applied Physics Laboratory at Johns Hopkins University who is presenting the Spitzer data

dmjspace · Sep 7, 2005

JonClarke said: Do you or do you not recongising the following as facts? Yes or no will suffice 1. There is not enough mass in the small bodies (comets, asteroids and dust) in the planetary solar system (ie. excluding the Kuiper belt and Oort cloud) to construct a planet larger than about 1/30th of the Moon - say twice the mass of Charon. The total mass of these bodies does not add up to a full planet. Nor should it be expected to under EPH premises. This appears to be a straw man argument, as there exists no model that suggests one simply add up the mass of the debris to get the parent body's mass. 2. The geochemical evidence unequivocally points to scores if not more than 100 parental bodies. I don't know. My question to you is that, if this is true, did the alternatives to the EPH predict this would be the case? Or did those alternatives simply accommodate these data? The EPH was modified because groups of asteroids shared characteristics suggesting a common parent body, as you say. It is reasonable, within the context of the model, that multiple planets exploded, the same way it is reasonable to assume that more than one supernova has occurred. If the events leading to the explosion of a star or a planet are natural products of stellar or planetary evolution, it would be ludicrous to suggest that such an explosion happens once and only once. In any case, what is the definition of a parental body? 3. The source of the asteroids lies between Jupiter and Mars. Yes. 4. The most plausible way to fragment a planet is through collision. The probability of collision being able to fragment a planet is very low, as far as I understand. It's implausible this happened. Whether another mechanism to fragment a plan

dmjspace · Sep 7, 2005

One last thing about the "parent body" issue. JonClarke is suggesting that the EPH is falsified because there are too many parent bodies for asteroids. I believe this is his area of expertise so I'm taking his word for it that groups of asteroids appear to have fragmented from larger bodies. That said, I fail to see how alternative models to the EPH fare any better, given the varied types of asteroids known to exist. Did the "solar nebula" hypothesis expect so many parent bodies? I don't think so. Did it expect *any* differentiated asteroids? Or does it insist comets and asteroids should all be pristine remnants? If it relies on collisions and early solar system heating to explain the observations, then I see little difference between it and the EPH, which suggests exactly the same thing: asteroids were formed in an explosive environment with extreme heating and violent collisions. But the EPH also predicts a host of other things--asteroid satellites, slow relative velocities, common rotation and orientation--that a random "solar nebula" theory does not, due to the differences in proposed time scales of the competing models. The standard model for the origin of comets and asteroids is struggling mightily with the same issues, as seen in this Nature article commentary, for example, entitled "Asteroids: Mantles were battered to bits".

mrmux · Sep 7, 2005

May I just say, gentlemen, that this continues to be the best thread on SDC, IMHO. Like a courtroom drama now! Jon is the expert witness and dmj is the hotshot lawyer. Excellent arguments and counter-arguments. Riveting stuff. BTW, I read in a UK paper today that a neutron star has been spotted bombing out into intergalactic space at a very unreasonable rate of knots (Massive Bullet Theory lives on!) Just above that paragraph was another mentioning the Japanese version of Deep Impact with it's goal of catching some debris for physical analysis. Finally, there was that stunning shot of the martian polar cliffs a few pages later. Great to see such things in a UK daily. I wonder if someone at that paper visits SDC...?

exoscientist · Sep 7, 2005

Thanks for the link to the NY Times article with the Lisse quotes, Dmjspace. I'm surprised that he doesn't understand the origin of the aqueous minerals in the spectra. The theory that radioactive heating could have allowed liquid water to form in comets early in the solar systems history is well known among comet researchers. In my opinion, the *only* reason why this theory was controversial was because it raised the possibility of life existing in comets, especially with the abundance of organic molecules known to be present in comets, also confirmed by Deep Impact. Bob Clark <div class="Discussion_UserSignature"> </div>

exoscientist · Sep 7, 2005

Thanks for the links, Telfrow. That low density for the comet is indeed quite puzzling, per the conclusion it is mostly empty space. Did they find the density to be less than water? The only other possibility I can think of is that - ulp- the comet is hollow .... Bob Clark <div class="Discussion_UserSignature"> </div>

dmjspace · Sep 7, 2005

exoscientist said: Thanks for the link to the NY Times article with the Lisse quotes, Dmjspace. I'm surprised that he doesn't understand the origin of the aqueous minerals in the spectra. The theory that radioactive heating could have allowed liquid water to form in comets early in the solar systems history is well known among comet researchers. This theory was developed *after* carbonate signatures were detected in prior observations. It can't be said that liquid water was predicted to have existed in comets. This is a prime example of accommodation. I guess Lisse is simply looking at the fundamental assumptions of his working hypothesis, which don't include liquid water in the dead cold 30K of space. What I find particularly interesting is that the spin that "everything we knew about comets is confirmed" has already begun despite some whopping surprises. How, for instance, can A'Hearn say in one interview that "There is no indication we got down to any solid ice," and then in a later interview say that, "Now, we can stop guessing at what's inside comets"? Is he really suggesting that "what's inside" the comet is (basically) nothing? How to explain the non-effect of the 800 pound probe moving at 23,000 mph, then? There's no doubt about it, the dirty snowball's preferred prediction was that there is one heck of an iceball underneath that dusty crust. What's more disturbing is the claim (made by the SDC writer, not the scientists interviewed) that Tempel 1 is "at least 50% water ice." As far as I understand, there is no way to determine what percentage of the total comet is water merely from the spectral data. It will be interesting to see what assumptions scientist use to make these determinations. Unfortunately for the dirty snowball model, today marks the day another article came out suggesting another body may have more water in it than our own planet...a

yevaud · Sep 7, 2005

Hmm. If Tempel1 was more like an asteroid than a comet (or what's supposed to be a comet), the output from the kinetic strike of the impactor would have been far more energetic, I'd think. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

exoscientist · Sep 7, 2005

Dmjspace said: "This theory was developed *after* carbonate signatures were detected in prior observations. It can't be said that liquid water was predicted to have existed in comets. This is a prime example of accommodation. I guess Lisse is simply looking at the fundamental assumptions of his working hypothesis, which don't include liquid water in the dead cold 30K of space." The theory of radioactive heating goes back at least to the 80's, perhaps earlier. I don't know if carbonate observed in carbonaceous meteorites predates this or not. (Carbonate actually *on* comets had not been observed before now.) But in any case I believe the actual origin of the theory was not the presence of carbonate in such meteorites but rather the presence of certain radioactive species in concentrations that suggest they could have produced large amounts of heating early in the Solar System. Bob Clark <div class="Discussion_UserSignature"> </div>

exoscientist · Sep 7, 2005

Jon, could those smooth areas in the just released Tempel I image themselves be carbonate or clay deposits? I'm thinking of something like karst terrain, as has been proposed for Mars: POSSIBILITY OF KARST MORPHOLOGY ON THE MARTIAN SURFACE AT THE MERIDIANI LANDING SITE FROM COMPARISON WITH TERRESTRIAL ANALOGS. Sz. Bérczi, Eötvös University, Department of General Physics, Cosmic Materials Space Research Group, H-1117 Budapest, Pázmány Péter s. 1/a. Hungary, (****@ludens.elte.hu) http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1051.pdf Bob Clark <div class="Discussion_UserSignature"> </div>

dmjspace · Sep 8, 2005

exoscientist said: The theory of radioactive heating goes back at least to the 80's, perhaps earlier. I don't know if carbonate observed in carbonaceous meteorites predates this or not. (Carbonate actually *on* comets had not been observed before now.) Yes, and the source of carbonaceous chondrites is universally thought to be asteroids, not comets. If one argues comets, too, should have carbonates normally formed only in the presence of liquid water, then we are one step closer to the EPH's main premise, which is that comets and meteorites formed in a similar manner, in a similar region, and will be shown to have similar nuclear densities.

dmjspace · Sep 8, 2005

I don't want to go off on too many tangents, as this discussion is getting pretty involved as it is. However, a new article in Astrophysical Journal is too good to pass up. In "New look at microwave background may cast doubts on big bang theory," scientists find data that strikes at the heart of expanding universe models. Pertinent to this discussion is the confirmation that the "cosmic microwave background," said to be a remnant of the big bang, is not behaving as predicted by that theory. Instead, the so-called CMB is more simply explained as a *local* disruption. The EPH has long explained the CMB as just that: the remnants of a local fireball, namely, the one that was created by planetary breakup. The reported discoveries have grave implications for the big bang's other assumptions, including the insistence that "red shift" always indicates distance. (Observerational evidence strongly confirms that this is not the case, according to astronomers like Halton Arp, for example.)

JonClarke · Sep 8, 2005

I look forward with interest to reading the Deep Impact papers in today's issue of science when my library gets it in a couple of weeks. But if there are web sites that claim A'Hearn as saying that our basic understanding of comets is wrong then they are misquoting him. I have heard A'Hearn in person. Deep Impact found ice, dust, organics, a low density aggregate structure. All expected. Perhaps if you explain what you think the "standard model" is then we might understand why you think that Deep Impact does not support it. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Sep 8, 2005

1. D The total mass of these bodies does not add up to a full planet. Nor should it be expected to under EPH premises. This appears to be a straw man argument, as there exists no model that suggests one simply add up the mass of the debris to get the parent body's mass. Wrong. Mass does not disappear, if there is not enough mass to make a planet than that mass has to have gone somewhere. he geochemical evidence unequivocally points to scores if not more than 100 parental bodies. 2. D My question to you is that, if this is true, did the alternatives to the EPH predict this would be the case? Or did those alternatives simply accommodate these data? They predict it. Accretion of a proto planetary nebula as proposed by Safranov and others will produce plenatismals, these accrete further to form small differentiated bodies which combine to form the rocky planets. TvF does not dispute this. Each differentiated body, large or small with have its own distinctive chemistry. That how we can differentiate rocks from the Moon, Mars, and Earth, for example. Safranov did his basic work in the 60's. 4. D The probability of collision being able to fragment a planet is very low, as far as I understand. Collisions were important in the early solar system. Not only is this predicted by modelling it is also consistent witrh observation. It is the most likely expanation for the retrograde orbits of Venus and Uranus. Miranda is a body that has framented and reaccreted. The most likely formation of the Moon is by giant impact. 5. That the majority of asteroids and all cometary material as not undergone melting and differentiation (added in edit) 6. Do you have specific sources? Typically 75% of asteroids are considered non-differentiated. Of the rest, 8% are metallic (definitely differentiated) and the remaining 17% contains both differentiated and non differentiated material. I suggest you <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Sep 8, 2005

The "new view of the asteroids" referred to in that nature commentary has been about since the 80's, in fact probably since the late 70's. The story of impacts and attrition amongst colliding bodies in that article is precisely the standard model you claim is under threat. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Sep 8, 2005

Subsurface melting in comets is entirely reasonable given the fact that they contain ice and are periodically heated. radioactive heating is also possible and predicted. That SDC story about Ceres illustrates precisely why you should not reply on news stories. I read that paper thismorning almost as soon as it cam out. The authors point out that the surface of Ceres shows no sign of water ice, although it does show the presence of hydrated minerals. The authors say they do not know the sate of water in the mantle of Ceres, whether it is hydrated minerals or ice. However the news story picks up the most dramatic interpretation and reports it as fact. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

exoscientist · Sep 8, 2005

Dmjspace said: "Yes, and the source of carbonaceous chondrites is universally thought to be asteroids, not comets." No, not universally. There are several varieties of carbonaceous meteorites. Some scientists believe the origin of some is from comets. Bob Clark <div class="Discussion_UserSignature"> </div>

exoscientist · Sep 8, 2005

Jon said: "But if there are web sites that claim A'Hearn as saying that our basic understanding of comets is wrong then they are misquoting him. I have heard A'Hearn in person. Deep Impact found ice, dust, organics, a low density aggregate structure. All expected." Jon, I thought A'Hearn was saying that it was expected that comets would have a more solid core. However, the density calculations suggest it is "fluffy" all the way through. This is surprising. Either that or it is hollow. Bob Clark <div class="Discussion_UserSignature"> </div>

yevaud · Sep 8, 2005

I'm not certain I can see how it could be hollow. Possibly more along the lines of fluffy ice, with intersticial pockets. Rather like a sponge. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

exoscientist · Sep 8, 2005

Yevaud said: "I'm not certain I can see how it could be hollow. Possibly more along the lines of fluffy ice, with intersticial pockets. Rather like a sponge." Yes I agree. I can't imagine any NATURAL way it could be hollow ... ;-) Bob C. <div class="Discussion_UserSignature"> </div>

yevaud · Sep 8, 2005

I can't imagine any NATURAL way it could be hollow ... Oh dear. That's opening yet another can 'o worms... (I wonder where you can buy cans of worms? Not at my local supermarket, certainly) <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

robnissen · Sep 8, 2005

"I can't imagine any NATURAL way it could be hollow ... " At the risk of showing my ignorance, it seems to me that if a comet started off full of volatiles, and then through countless orbit around the sun the volatiles were burned off, couldn't numerous large hollow pockets eventually form.

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