Where's the discussion on Stardust data?

tdamskov · Mar 20, 2006

Bonzelite, I don't see how comets would not primarily originate from within our solar system. Here's why, based on observations. The solar system is moving through the interstellar clouds at a relative velocity of 26 km/s. At that speed you would expect to see interstellar "dust lane" comets arriving in the solar system with a bias in direction and velocity opposite to the orbit of the solar system around the galaxy core. But comets don't have that bias.

CalliArcale · Mar 20, 2006

<blockquote>In reply to:<hr />yes, borman and i have both hypothesized comets, at least some of them, to be far older than sol itself, as they may be ancient wanderers gathering superfine dust in the vast lanes of the galaxy.<hr /></blockquote> Actually, I was thinking more along the lines of the comets having formed with the solar system, but because they are so low in mass, the bits of stuff they formed from would've had a better shot of surviving accretion intact. I think this is what the Stardust team hopes as well, because if it were true, it would mean that comets are a priceless repository of material from the protoplanetary cloud, virtually unchanged over the last few billion years. This has little value in terms of commercial exploitation, but would be beyond price in terms of scientific value. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

siriusmre · Mar 20, 2006

I notice that in all this discussion of quiescently frozen fluff balls no one has made any mention of the craters that are present on the surfaces of comets--at least the ones that we've seen! All give evidence of some sort of tortured past. Clearly comets are substantial enough that they are able to maintain stark surface features, and yet everyone can agree that they are not substantial enough to have withstood the apparent number of impacts that many of them seem to have endured. This strains credulity. It is beyond self-evident that comet surfaces appear mostly bone-dry and appear to be made of substantial, rocky material; at least substantial enough to maintain sharp surface features. I guess the counter to this would be the lame assertion that the comets that we have examined up close represent comets which have lost most of their surface "volatiles" and are simply showing the rocky remainder of an "outgassed" surface. But, I thought that Wild 2 was supposed to represent a "young" comet...? Is that characterization no longer operative? On the other hand, there is a strong analog between the surfaces created right here on Earth in plasma etch chambers (or other applications of electric discharge machining) and those seen on the surfaces of comets. Not only that, EDM is capable of producing all of the phenomena seen on comets from surface morphology to particulates and elements found in cometary coma and tails. I understand that to see this requires, in some cases, a world-view-shattering alteration of paradigm; and; as such, can be threatening, and downright scary. I just ask those folks to be open to examining something new in light of this "shocking" new data. <div class="Discussion_UserSignature"> </div>

bonzelite · Mar 20, 2006

hello Shadow. I find it interesting that you have put so much stock in so very very little information. i knew water was below mars, as a fact, with such little information and amid cautionary skepticism. i've suspected comets to be, at least in part, from extrasolar origins. some scientists are now publically saying this, too. impossible? maybe. possible? maybe. probably. look at Enceladus. it is "impossible." "shouldn't be there." it is the embodiment of the contrary view --made real-- that flouts and gives the middle finger to the scientifically negligent and misleading headlines purporting fallacy and myth. but look at Enceladus --it is there, laughing at all of us. had i suggested such a body exists with what it is doing, you would have called me an idiot and would have banished my thread to phenomena. but look at it. look at Enceladus and behold how we don't know anything. Likewise, our knowledge of solar systems comes almost exclusively from a sample of one, with an extremely small amount of scattered, but woefully incomplete data from a few nearby stars. Until we have a VVLAT looking at distant stars, we won’t be getting sufficient data to draw any conclusions one way or the other. your preaching to the choir, Shadow. such as the reason why declaring so boldy how solar systems come to be, core accretion theory with rocky planets first out to gaseous ones farther out, is entirely premature and overly enthusiastic. and probably wrong. take your own advice. likewise, i could be entirely wrong. and i admit it. others will naysay and skepticize their merry way down the street, spreading hate and contempt for anything different. to them, the official theories are all axioms. and dissenters are to be cast to hell. My point is, what is the purpose of getting so excited, so offended, and so bell

mental_avenger · Mar 20, 2006

You might find some of my beliefs to be controversial. For all the “evidence”, the Oort cloud is still only a hypothesis. The advent of comets does not necessarily depend on the existence of such a “cloud”, at least not as it is currently hypothesized. In my recommendations for an asteroid/comet protection system, I allow for the probability that some comets or asteroids are interstellar bodies. Although probably arriving near the plane of the ecliptic, they would not be predictable because they would not be periodic, but rather solitary events. That is why asteroid/comet detection should begin out beyond the orbit of Mars with a total of at least 12 equally spaced detectors. such as the reason why declaring so boldy how solar systems come to be, core accretion theory with rocky planets first out to gaseous ones farther out, is entirely premature and overly enthusiastic. You misunderstand. Our sample of one allows an analysis of this solar system in depth, but limits us to this solar system. As such, although we may be able to determine with some certainty the formation of this solar system, we cannot make accurate predictions on the formation of other solar systems. By the same token, we cannot use vague and incomplete data from a very few distant solar systems to attempt to analyze ours. maybe look in the deep mirror sometime and ask yourself the same question, Shadow. I do so, often. But I rarely get excited about these discussions anymore. If you saw me typing these posts you would note calm objectivity. why moderate, then? To prevent flame wars. To head off heated arguments before they start. It is sad that such Moderation is even required here. Of course the other part of Moderation here is to try to keep threads from being derailed or hijacked by a few aggressive members, spoiling the discussion for everyone else. It is always a difficult call.<</safety_wrapper> <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

bonzelite · Mar 20, 2006

In my recommendations for an asteroid/comet protection system, I allow for the probability that some comets or asteroids are interstellar bodies. Although probably arriving near the plane of the ecliptic, they would not be predictable because they would not be periodic, but rather solitary events. That is why asteroid/comet detection should begin out beyond the orbit of Mars with a total of at least 12 equally spaced detectors. i agree with this ^^^. some celestial objects may arrive from the polar directions of Sol as well, coming from "out of nowhere." such dectectors should be arrayed, too, in circumpolar orbits. By the same token, we cannot use vague and incomplete data from a very few distant solar systems to attempt to analyze ours. yes we can. and the more we begin to see clearly other systems over time, we will look to ours more and more in comparison. they've already discovered a system whose disk of material is stratified with orbits of material rotating both clockwise and anticlockwise, prograde and retrograde, to the sun --completely at odds with what was thought as a slam-dunk axiom of planetary orbits, ie, that all planets must orbit the sun in the same direction as the sun's rotation --prograde. this is not true. super giant and super hot gas jupiter-type planets have been observed to orbit so close to the sun that the planet nearly touches the sun. this flouts terrestrial rocky planet/nearest to sun theory. maybe our own system was configured in such a way long ago. i think we should consider that as a possibility. therefore, when we look out to other systems, we may gain incredible insight into solar development in general, piece by frustrating piece. what we assume to be true in this system may not be true for this system whatsoever. indeed, not all systems are the same. they're as varied as individual pe

CalliArcale · Mar 20, 2006

<blockquote>In reply to:<hr />I notice that in all this discussion of quiescently frozen fluff balls no one has made any mention of the craters that are present on the surfaces of comets--at least the ones that we've seen! All give evidence of some sort of tortured past. Clearly comets are substantial enough that they are able to maintain stark surface features, and yet everyone can agree that they are not substantial enough to have withstood the apparent number of impacts that many of them seem to have endured.<hr /></blockquote> I think you misunderstand what others are saying. Nobody is arguing, much less agreeing, that comets are too insubstantial to endure bombardment. On the contrary, most of us here (and certainly most scientists) are describing them as heavily bombarded objects. It is not impossible for a loose object to have craters. The size of these objects is such that words like "fluffy" may give a false impression; it's only fluffy on its scale. On our scale, it's probably quite solid. What this implies to me is that the surface of these comets is very ancient. Very few comet nuclei have been imaged in close detail. I suspect that if we image enough, we'll find that the young ones appear heavily bombarded and the old ones are all smoothed out due to the geologic activity that appears to occur when they approach the Sun. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

bonzelite · Mar 20, 2006

what prevents me from falling in love with the casual idea of yet more impactors on the pockmarked surfaces of coma is simply that it has been "hit" from every conceivable angle, by very large impactors, to hit a very tiny, nearly gravity-free attracting body. and i'm just not buying it. i'm more inclined to believe the pockmarking is created from the jetting events over aeons of time. or something else, like the dreaded and oft-hated electrical machining process. the markings do not resemble impact events really. and as i said, the object is nearly completely covered with large pockmarkings, to the extent it is nearly totally enveloped in such markings. it's complexion is extremely bad for such a small object. what i'm saying is that pockmarking may not be a slam-dunk for dating the surface. one such huge impactor would have vaporized the comet. the coma looks more like a huge piece of pumice or of some other air-pocketed magma bomb of volcanic origin. can i be wrong? of course. yes. my opinion needs more verification with data. but impactor origins for the markings seems in this case very far afield. try again.

bonzelite · Mar 20, 2006

comet on the ground:

siriusmre · Mar 21, 2006

Exactly, bnonz! It seems to me that it would be flatly IMPOSSIBLE for comets to have endured--never mind attracted!--the scale of supposed bombardment that they have apparently suffered. Especially if they are supposed to be so (relatively) loosely conglomerated in the first place. Craters on comets may not come from highly improbable impacts or "outgassing" at all. In fact, I'm betting that one day we will confirm that they don't. <div class="Discussion_UserSignature"> </div>

derekmcd · Mar 21, 2006

Looks more like vomit on the ground <img src="/images/icons/wink.gif" /> Sorry, i just couldn't resist. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

siriusmre · Mar 21, 2006

<blockquote>In reply to:<hr />I suspect that if we image enough, we'll find that the young ones appear heavily bombarded and the old ones are all smoothed out due to the geologic activity that appears to occur when they approach the Sun.<hr /></blockquote> I'm laying my "money" on exactly the opposite coming to light. I believe that the more and closer we look at comets the more we will discover that they ALL have craggy surfaces that exhibit sharply defined features, such as pits and craters. And, how will we know the "young" ones from the "old?" Crater count? If we do find some comet with a smooth surface, will it be interpreted so blithely as being an old comet simply because that's what the model says? Or will there be another, better, more impirical way to measure a comet's age that does not change the data (perhaps mistakenly calling a young comet an old one, for example) to fit the hypothesis (young comets should appear to be heavily bombarded and old ones should appear smooth, for example)? I do not put alot of stock in the crater counting method of aging. <div class="Discussion_UserSignature"> </div>

maxtheknife · Mar 21, 2006

Sirius: I do not put alot of stock in the crater counting method of aging. Me neither!

bonzelite · Mar 21, 2006

Looks more like vomit on the ground the vomit comet comes to town <img src="/images/icons/smile.gif" /> there's just other ways to get pockmarks onto surfaces. and impacts are not the only game in town, particularly if you just consider the surface they're allegedly on. a comet's surface doesn't make sense to me to be full of impacts. it's like calling a table with 4 legs a "dog" because a dog has 4 legs.

bonzelite · Mar 21, 2006

i agree with some, and disagree with some: We know cometary density figures show very clearly that they are NOT substantially more than water density. We know that they must contain large amounts of empty spaces. yes, like volcanic pumice. pockmarked to death with many inner voids and very lightweight. an air rock. That they can withstand bombardment over billions of years, despite this, is a matter of fact. now that is unknown. highly unknown.

CalliArcale · Mar 21, 2006

<blockquote>In reply to:<hr />what prevents me from falling in love with the casual idea of yet more impactors on the pockmarked surfaces of coma is simply that it has been "hit" from every conceivable angle, by very large impactors, to hit a very tiny, nearly gravity-free attracting body.<hr /></blockquote> Why couldn't they be bombarded as much as, say, Phoebe? Truthfully, the mass of the object being bombarded has little to do with it. Even Earth doesn't have powerful enough gravity to significantly affect the rate of bombardment. It is a popular myth that massive objects suck in impactors by their sheer gravity, but it's not true. The impactors are generally going far too fast for that to matter much. So the rate of bombardment is not related to the mass of the object. The actual logic behind dating based on crater counts is related to the surface of the object, not hte object itself. You can't tell how old an object is by how many craters it has. However, you can get a good idea of how geologically active it is, because areas with fewer craters are probably younger. If you get really lucky, you can stumble upon a giveaway like a half-covered crater. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

dmjspace · Mar 21, 2006

Despite all the tap dancing, there's no getting around the fact that the kind of porous object scientist suggest comets are would fracture, shatter or spin wildly upon significant impact. Dating by crater count is inane, and many scientists are finally starting to admit that. (See, for example, Crater count led Mars historians astray ) The best explanation for craters on comets and asteroids is that they were formed in an explosive environment that included intense bombardment, AND that they are solid objects. To date, ALL estimates of comet density are mere guesses, and likely not even educated guesses. The numbers we have today have huge uncertainties, so much so that all comet densities "bleed" into ranges for average asteroids. Statistically, by all of our best estimates, comets are no different in density than a run of the mill asteroid. Acknowledgment of this fact should eradicate invention of exotic theories regarding fluff balls, styrofoam or aerogel-like compositions. They are unnecessary hypotheses. Comets are solid bodies and they are cratered because they can withstand cratering, just like any other big rock. Cratering, intense heat, evolved surfaces, the absence of expected water content, and the presence of compounds such as olivine, salts and carbonaceous material are all most compactly explained by the exploded planet hypothesis. The dirty snowball model needs extensive patching due to the equally extensive list of unpleasant surprises the observations keep bringing to the table. I find it ironic now that critics are more than willing to accept a new variable in the dirty snowball model requiring nuclear reactions ("radiogenic heating"), but they continue to scoff at nuclear reactions as a potential mechanism for a planetary breakup.

robnissen · Mar 21, 2006

What would be interesting would be to compare the average crater count per square meter (or whatever) on the moon, with Phoebe and with the well-imaged comets. My guess is that the average count would not differ much.

yevaud · Mar 21, 2006

To date, ALL estimates of comet density are mere guesses, and likely not even educated guesses. The numbers we have today have huge uncertainties, so much so that all comet densities "bleed" into ranges for average asteroids. Statistically, by all of our best estimates, comets are no different in density than a run of the mill asteroid. Comet densities have been estimated (and in some cases, actually determined via observational data) at between 1.0 gram per c^-3 - 2.0 gram per c^-3. That indicates the presence of significant volatiles. H20 has been detected radiometrically. Take for example the ESA findings on comet LINEAR: Comet LINEAR. You will note the detection of vast quantities of released H20. Or the findings of comet Comet 67P / Churyumov - Gerasimenko: Comet 67P / Churyumov - Gerasimenko Comet Hyakutake: Comet Hyakutake Spectra of Comet Ikeya/Zhang: Ikeya Zhang In all of those cases, many volatiles were detected, including O, H, and H20. Now truth be told, Deep Impact *did* produce some surprises: Tempel - 1 Although these do not invalidate the presence of H20, and other volatiles; nor that of significant presence of dust. Mostly, Comets turn out to be pretty complex. Acknowledgment of this fact sh <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

siriusmre · Mar 21, 2006

What would that tell us, though? Especially if we are not 100% sure what causes cratering in the first place, or that it is a valid measure of anything useful...? <div class="Discussion_UserSignature"> </div>

bonzelite · Mar 21, 2006

This is a contradiction, isn't it? If they're "mere guesses," then why are your guesses any better than those of the professionals? Not certain I follow this line of reasoning. let me elaborate: "official guesses." and if you go astray of official guesses, then this is what you get: denial and naysaying.

yevaud · Mar 21, 2006

Addendum: In fact, if no one has any vast objections, I will make minor useage of my MCT role, and suggest that we now have too many highly similar threads ongoing here. Far too redundant: 1. Where's the Discussion of Stardust Data? 2. The formation of Solar Systems. 3. What's going on with comets? 4. Deep impact update. 5. Special interest: our solar system. I will request that the Mods lock some of them, and we can combine the remainder into a few relevant threads. One on comets in general, one on Solar System formation, work for all of you? <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

bonzelite · Mar 21, 2006

sure.

yevaud · Mar 21, 2006

Ok. Request made then. Since all of these topics really fall into about two categories, that appears to be what would make the most sense. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

CalliArcale · Mar 22, 2006

Any preference as to which ones should stay? I can take care of the locking -- I finally have net access again! Whee! <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

Where's the discussion on Stardust data?

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