Deep Impact Predictions

[exoscientist]

RobNissen wrote:<br />"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."<br /><br /> Good point Rob. I hadn't thought of that. But I would think this process would work only near the surface, not all the way through.<br /> However, for theories that propose radiogenic heating allowed liquid water in their cores, this water may have evaporated over millions of years due to this internal heating. This could leave voids in the interior of the comet.<br /> But a question would be whether once turning to gas could this water vapor escape from the confines of the core of the comet? After the radiogenic heating cooled off, if the water vapor did not escape, it should refreeze and the density should still at least be that of water. <br /><br /> Here are some references to the theory of radiogenic heating in comets:<br /><br />The Net Advance of Physics: ANNOTATED BIBLIOGRAPHIES, No. 1 <br />Panspermia Theories: Annotated Bibliography, Section V <br />ORGANIC GRAINS, PREBIOTIC CHEMISTRY, AND LIFE ON COMETS: <br />http://web.mit.edu/afs/athena.mit.edu/user/r/e/redingtn/www/netadv/bioast/clash/comets.html <br /><br />M. Wallis, 1980 Nature 284:431. <br />Argues that the center of a comet would be originally liquid, due to <br />Aluminum-26, and potentially hospitable to life. <br /><br />A. BarNun, et al, 1981 Origins of Life 11:387. <br />Attack the idea of Hoyle and Wickramasinghe that life arose in <br />comets. Most organics are sublimed or blown off at perihelion in too <br />short a time to migrate into interior; the structure is too tenuous <br />for a liquid core; if there were a liquid core (due to Aluminium-26), <br />it would be too radioactive for life. <br /><br />E.K. Jessberger and J. Ki <div class="Discussion_UserSignature"> </div>

 

[JonClarke]

As I recall people have suggested for years that comets are low density spongy objects. Maybe A'Hearn was expecting something for solid at the core. But I don't think this is a given for all comets. Comets are highly individual objects, despite their small size. <br /><br />LINEAR had the lowest density of any comet measured - 0.03! Halley also has a low density (0.1), Wild somewhat higher (0.36). Borrelly's density is less well known, between 0.18-0.3.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>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</em>  Arthur Clarke</p> </div>

 

[JonClarke]

I think you are right and that how objects between 1 m and perhaps 10-100 m stickly is poorly understood.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>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</em>  Arthur Clarke</p> </div>

 

[exoscientist]

Thanks for those density numbers Jon. I thought it was assumed comets had a solid core.<br /> I'll ask some of the authors of those papers on radiogenic heating in comets if this could allow water to evaporate leaving voids in the comet.<br /><br /> Bob Clark <div class="Discussion_UserSignature"> </div>

 

[serak_the_preparer]

Not a scientific paper, per se, but an interesting article nonetheless:<br /><br />Comet’s minerals hint at liquid water by Maggie McKee, Cambridge, UK (NewScientist)<br /><br />08 September 2005<br /><br /><i>"How did clay and carbonates form in frozen comets?" says Carey Lisse, an astronomer at the University of Maryland in College Park, US, who observed the impact with Spitzer. "We don't know, but their presence may imply that the primordial solar system was thoroughly mixed together, allowing material formed near the Sun where water is liquid, and frozen material from out by Uranus and Neptune, to be included in the same body...."</i>

 

[mrmux]

It's this thread that keeps me sane... Please keep going, folks.<br /><br />A question for Jon (and anyone);<br /><br />Is there any truth to the assertion that comets basically come from any heading, and don't tend to be grouped around the ecliptic?<br /><br />If so, is that a problem for current theories of how comets formed?

 

[JonClarke]

Ye, comets can from from any angle. As I recall it was the existence of highly inclined and often retrograde orbits of long period comets, combined with their volatile-rich nature that led to Oort postulating his famous spherical cloud on the frontiers of the solar system from which cometrs were peturbed inwards.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>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</em>  Arthur Clarke</p> </div>

 

[jatslo]

Jatslo's Prediction:<br /><br />"Petroleum Products", "Water", "Rocks", and the first ever possible biological evidence detected outside of Earth's atmosphere.

 

[dmjspace]

JonClarke said: <font color="yellow"> LINEAR had the lowest density of any comet measured - 0.03! Halley also has a low density (0.1), Wild somewhat higher (0.36). Borrelly's density is less well known, between 0.18-0.3. </font><br /><br />You speak as if these density figures are known within a small range. stevehw33 is the only other poster around here who dared to put specific numbers out regarding comet densities.<br /><br />The fact is that each of these figures is controversial. The figures that stevehw33 posted for Tempel 1 earlier had an allowable error which encompassed an entire order of magnitude.<br /><br />stevehw33 and the other snowball supporters refuse to acknowledge that such numbers are merely guesstimates that were arrived at with a specific model in mind.<br /><br />Regarding LINEAR's density figures, a SWAN (a SOHO instrument) scientist admitted as much when he said, "Our opinion about [LINEAR's] low density is tentative and controversial."<br /><br />The density figures are model dependent. Deep Impact went to measure what was beneath the dusty (and apparently deep) regolith. There is no guarantee that the probe even got below Tempel 1's surface.<br /><br />In fact, it's not even clear which densities we're arguing about here. Are the figures snowball proponents offering a density of coma plus nucleus? Just the nucleus? Just the coma? Just the regolith covering Tempel 1?<br /><br />In the EPH, if one includes the coma and the nucleus in density measurements, the overall density will be extremely low. But when I refer to density I'm referring only to the nucleus (or nuclei), which are asteroid-like.<br /><br />As far as A'Hearn being misquoted...I suspect we'll hear different statements out of him later as he modifies his view to be more in line with expectations. After all, too many acknowledgments of "surprises" in the data may lead one down a path he'd rather not go.

 

[dmjspace]

JonClarke said: <font color="yellow"> 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. <br /><br />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. <br /><br />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. </font><br /><br />Look, I've been asking dirty snowball proponents for <i> weeks </i> to define their preferred model in terms of specific predictions, and we've yet to hear anyone stick their neck out on that question.<br /><br />The model is apparently so vague that practically any finding can be accommodated. This is my primary complaint with the dirty snowball concept, which has evolved from iceball to dirty snowball to snowy dirtball to snowy mudball. It will undoubtedly morph further. Already it is becoming a model allowing for the idea that "every comet is unique." This may be a nice general concept, but it doesn't do much for prediction.<br /><br />You say: "Deep Impact found ice, dust, organics, a low density aggregate structure."<br /><br />The only thing in this sentence that differentiates the model from others (namely the EPH) is the suggestion of a low density aggregate. Yet, if Tempel was covered with what some scientists have suggested was a 30m regolith, it would be incorrect to assume that's what the comet nucleus is made of.<br /><br />DI was supposed to help us penetrate the nucleus's crust, not just the dusty coating. The lack of increased water vapor (it *decreased* post-impact, according to Earth based telescope data) and UV flash (indicating a very hard surface below the regolith) certainly don't seem to fit the expectations of the dirty snowball model in its curr

 

[dmjspace]

JonClarke said: <font color="yellow"> 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. </font><br /><br />And, yet, it appears that all the news articles that have been released supporting the "standard" view of comet are okay for me to believe? (Except for the ones in which scientists are "misquoted" when they contradict the snowball model, of course.)<br /><br />I, too, would prefer to have the actual data interpreted, unfettered by mere science journalists, by experts. It looks like those articles are coming out shortly. <br /><br />Hopefully we will be treated to an open discussion which includes consideration of all models on the table, rather than an exercise in accommodation for the dirty snowball model.

 

[JonClarke]

Please define what you think is meant by "the standard model".<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>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</em>  Arthur Clarke</p> </div>

 

[dmjspace]

A favorite "dirty snowball" supporter website, Wikipedia, provides the best summary of the standard model on comets, here. <br /><br />The key prediction is that comets are dominated by ice. (If they weren't, they would be little different from asteroids.)<br /><br />Obviously, there is a debate over composition, which is why we went to Tempel 1 in the first place. Or, as the source above notes,<br /><br /><i> Debate over comet composition<br /> <br />Comet Borrelly exhibits jets, yet is hot and dry.As late as 2002, there is conflict on how much ice is in a comet. NASA's Deep Space 1 team, working at NASA's Jet Propulsion Lab, obtained high-resolution images of the surface of comet Borrelly. They announced that comet Borrelly exhibits distinct jets, yet has a hot, dry surface. The assumption that comets contain water and other ices led Dr. Laurence Soderblom of the U.S. Geological Survey to say, "The spectrum suggests that the surface is hot and dry. It is surprising that we saw no traces of water ice." However, he goes on to suggest that the ice is proabably hidden below the crust as "either the surface has been dried out by solar heating and maturation or perhaps the very dark soot-like material that covers Borrelly's surface masks any trace of surface ice".[4]<br /><br />The recent Deep Impact probe has also yielded preliminary results suggesting there is less ice in comets then originally predicted. </i><br /><br />The key is what was originally predicted. And so far, every observation, near or far, of every comet has resulted in the discovery of <b> significantly less ice than expected. </b><br /><br />The standard model maintains that ice will dominate, necessitating a nucleus density lower than an asteroid. <br /><br />The EPH says comet nucleus densities will follow the range of asteroids, because they (comets) are mostly rock.

 

[dmjspace]

One of the corollaries of the EPH is the satellite model of comets and asteroids. In a planetary breakup, a logical consequence of the explosion is many asteroids and comets with satellites, some even with multiple nuclei.<br /><br />This scenario is virtually forbidden in the solar nebula model, because any such satellites would have de-orbited or been perturbed out of orbit long ago. The "standard model" is so sure of this that Van Flandern won a bet with one of the Deep Impact team members when it was subsequently discovered that asteroid moons are not uncommon.<br /><br />What the mainstream model considers "breaking up" of comets (such as Hale-Bopp) is simply the separation of orbiting satellites in the EPH corollary. Unfortunately, since comets are not supposed to have satellites, scientists have decided that comets must break up because of extreme fragility. This assumption has led to what are probably vastly underestimated nuclear densities for comets.<br /><br />But, as Deep Impact showed us, Tempel 1 withstood, without any apparent lasting effects, a shot to the heart at 23,000 mph. What styrofoam-like, "mostly empty" body with little gravitational influence would behave like that?<br /><br />The mental gyrations one must go through to hold the "comets are light 'n' fluffy" model together in the face of this new data are numerous indeed.

 

[yevaud]

A fine picture indeed.<br /><br />Interesting as well, that you can see icy material peeping through the thin veneer of material on the surface.<br /><br />And in answer to the comment about the impact with respect to the composition of Tempel1, if it was a solid object, e.g. not "fluffy," the impact would have generated a much larger energetic output, which would have easily been detected by the imaging instrumentation - and it wasn't seen. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[dmjspace]

The EPH predicted a transient cloud of debris, from the deep regolith of ashy dust. The comet would otherwise remain undisturbed. <br /><br />Not bound by the gravity dominated model expected by NASA, the dust would not fall immediately back to the surface but would instead escape, creating a backscattering of sunlight.<br /><br />This is exactly what happened. The UV spike seen at impact suggests a hard object covered with dust.<br /><br />But that is the least of the snowball model's worries at the moment.<br /><br />A new report shows the discovery of abundant green sand crystals in Tempel 1's debris cloud.<br /><br />If these crystals are indicative of olivine, which is likely, then the standard model is faced with yet another mystery. This problem became evident with analysis of Hale-Bopp's spectrum.<br /><br />According to Dr. Joseph Nuth, Supervisory Astrophysicist at NASA's Goddard Space Flight Center, "Observations in 1989 found crystalline olivine dust in comet Halley. Our research placed severe constraints on how fast this dust crystallizes, and we realized that Halley could not have formed the way astronomers think it formed." <br /><br />Woops.<br /><br />Worse yet, as reported in the same article: <br /><br /><i> At the very low temperatures, where water-ice and the other volatile components of comets are frozen, the time required for amorphous silicate dust grains to change to the crystalline olivine found in comet Halley is many times longer than the age of the Universe. </i><br /><br />Quite a conundrum for the dirty snowball model of comets.<br /><br />Naturally, instead of examining the fundamental assumptions of the model, scientists rapidly began imagining new ways for olivine to be present in comets. They

 

[exoscientist]

Thanks for the links on olivine in comets, Dmjspace. I had seen the report on olivine detected in Tempel I but I hadn't realize the connection to heating.<br /> This would also be consistent with the theory of radiogenic heating in comets.<br /> Note as well that crystalline ice, rather than amorphous ice, was seen on a deep Kuiper belt object that also suggests such heating took place early in the solar systems history and may be occuring currently:<br /><br />Chilly Quaoar had a warmer past<br />Mark Peplow <br />Crystalline ice suggests remote object has radioactive interior.<br />Published online: 8 December 2004.<br />http://www.nature.com/news/2004/041206/pf/041206-7_pf.html<br /><br /><br /> Bob Clark <div class="Discussion_UserSignature"> </div>

 

[dmjspace]

exoscientist said: <font color="yellow"> Thanks for the links on olivine in comets, Dmjspace. I had seen the report on olivine detected in Tempel I but I hadn't realize the connection to heating. <br />This would also be consistent with the theory of radiogenic heating in comets. </font><br /><br />The EPH still sounds simpler to me. We know that liquid water can lead to carbonates, olivine and crystalline ice. Liquid water on a parent planet, of which the comet is simply a fragment of, may explain the evidence in a more compact way.<br /><br />Maybe I'm missing something, but I don't see how evidence of radiogenic heating can serve to differentiate between the EPH and other models of comet formation. After all, radiogenic heating is thought to have occurred in planets (or may still be occurring). In the EPH, comets are simply parts of a former planet.<br /><br />One important difference is that the EPH necessarily predicts evidence of nucleosynthesis (from prior differentiation in the parent planet and the explosion event itself), whereas the dirty snowball model did not originally expect the materials observed.<br /><br />As a sidenote, here's an interesting quote from researchers at NASA, from the paper "Evidence for Liquid Water on Comets". It demonstrates just how quickly the dirty snowball's failed predictions are forgotten as they are being patched with ad hoc arguments.<br /><br /><i> The albedo prediction before the Halley flyby was 0.7-0.3 for dirty snow, so Halley’s 0.03 albedo came as a great surprise. Since this is blacker than almost everything but carbon soot, it immediately generated suggestions on how carbon containing volatiles could transform into carbon black....[A]ll three comet flybys have found essentially the same low albedo surfaces, with no albedos anywhere suggestive of dirty snow. </i><br /><br />Another order-of-magnitude miss (a variability similar to the allowable errors in current dirty snowball density estimates). <br /><br />One would h

 

[dmjspace]

Predictably, the standard model of comets is slowly but surely morphing into a theory indistinguishable from the EPH, as more and more articles appear with titles similar to the one seen today at PhysOrg: Evidence for more dust than ice in comets .<br /><br />Clearly, the newest and best observations of comets support the EPH, which says that comets are little different from asteroids. They do not support the dirty snowball model.<br /><br />It is time to consider alternate theories of comet origins and composition.

 

[centsworth_II]

<font color="yellow">"...the standard model of comets is slowly but surely morphing into a theory indistinguishable from the EPH..." - dmjspace</font><br /><br />If the standard model can so easily accomodate the observations and predictions of the EPH (minus the exploded planet), it is a very robust model indeed. The image I get is of the standard model snake ingesting the EPH mouse, digesting what is useful and excreting the useless parts. <div class="Discussion_UserSignature"> </div>

 

[Philotas]

How on Earth can an 'exploded planet' be explained; with a Death Star? The whole EPH sounds ironic. <div class="Discussion_UserSignature"> </div>

 

[maxtheknife]

Centsworth: <font color="yellow">The image I get is of the standard model snake ingesting the EPH mouse</font><br /><br />How interesting you should say that. The image I get is one that is commonly used in business when a smaller company buys out a larger one. The metaphor is: The mouse sometimes swallows the elephant. <img src="/images/icons/smile.gif" />

 

[dmjspace]

centworth_II said: <font color="yellow"> If the standard model can so easily accomodate the observations and predictions of the EPH (minus the exploded planet), it is a very robust model indeed. </font><br /><br />Who said anything about easily?<br /><br />You seem to be suggesting that a model that makes few predictions, fails at the ones it does make, and needs to change in fundamental ways with every new observation, is a "robust" model.<br /><br />Scientifically speaking, a model fitting the above criteria is the exact opposite of robust, i.e. weak, ever changing, rife with degrees of freedom.<br /><br />Contrary to popular belief, a model that accomodates new findings by adding helper hypotheses is NOT ideal. It is inferior.<br /><br /><font color="yellow"> The image I get is of the standard model snake ingesting the EPH mouse, digesting what is useful and excreting the useless parts. </font><br /><br />The image you *should* get is the standard model snake magically transforming into a mouse itself. But magic is not allowed in science, so why bother with the snake at all?

 

[dmjspace]

A recent study of Mars Global Surveyor data from UC-Berkeley scientists provides more confirmation of the "exploded planet hypothesis" (EPH).<br /><br />As is usually the case, the mainstream model of Mars' formation is confounded by the data.<br /><br />In the PhysOrg.com article "Hundreds of auroras detected on Mars", the scientists expressed shock over evidence of what appears to be magnetized crustal regions, which give rise to unexpected Martian aurorae akin to planet Earth's "northern lights."<br /><br />The EPH predicts that Mars' atmosphere and magnetic field were stripped away by the debris from the nearby explosion of its parent planet. <br /><br />The EPH logically predicts embedded magnetic chunks from the former planet's core to reside in Mars' surface. The chunks would be arrayed in an apparently random manner, giving rise to chaotic magnetic fields. Prior evidence already confirmed these predictions.<br /><br />But the stunning thing about the UC-Berkeley report is the image in the article depicting the current magnetic fields on Mars. It speaks volumes in support of the EPH. According to the article, "[M]ost of the remaining magnetic fields are in the southern hemisphere."<br /><br />In the EPH, Mars was violently splattered with debris after the parent planet exploded. This is why the southern half of Mars is caked with an extra several miles of rock.<br /><br />Mainstream models will need to invent yet another helper hypothesis to explain why the northern hemisphere is devoid of magnetic fields, just as they had to invent a way for the northern hemisphere to have "lost" several miles of crust. (It didn't lose it, the bottom half of the planet simply had a large amount of debris caked on to it.)<br /><br />For more on the mounting evidence for the EPH and its consistency with what we know about Mars' history, see this link

 

[bonzelite]

the accepted model for the residual mag fields is that the planet, being smaller, cooled sooner after being bombarded and molten, losing it's active inner core relatively early. this killed the active planetary mag field but left fossilized mag traces in the geology (the demag'd mars, then, lost it's magnetic sheath that protected against incoming charged particles that then ate away most of the atmosphere. sounds pretty tight and sensical an idea to me). <br /><br />the thing is, why, then is only the southern pole seemingly magnetically active, even if it is fossilized? <br /><br />would it be because of subsurface ice and sand at northern latitudes is thicker and more prevalent, thus less likely to magnetize -- versus more widely abundant subsurface bedrock and surface highland rock at the south? <br /><br />i would not rule out EPH. but i would not jump to rule out the accepted view. mind you, we're very very early in the game of mars. so there are centuries of exploration ahead of humanity on this issue. we are just really beginning to dig into the trove of mysteries on that world. and it is very tantalizing and frustrating all the same. <br /><br />this unavoidably makes me think of Enceladus and it's own active southern hemisphere and pole. why is that world, too, active on it's southern pole only? is this coincidence or a pattern of something?