What's Going on With Comets?

[yevaud]

Tell me: Statistically, how likely is it that all cometary material is of extrasolar origin? Given the sheer volume of space even between us and the nearest other solar system? I think you underestimate this by a huge amount.<br /><br />Further - and this has not been mentioned - if we *did* capture cometary material of extrasolar origin, whatever makes you think it would be composed of greatly different material than we observe already? <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>

 

[yevaud]

Yes, but NASA didn't suggest all cometary material was of extrasolar origin either. Don;t mistake their covering all possible bases there as meaning this *is* what Stardust has captured. <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>

 

[jatslo]

Stardust is a sample of 1; therefore, the hypothesis is testable, and *REJECTING* it requires another sample with different results, I am sorry to say. That is just the way it works. NASA probably had several hypothecations, but two had higher confidence intervals, so they reported in that fashion. They have a high degree of confidence that they can narrow the hypothecations to just one, once they test the other sample. Right now its 50:50.

 

[bonzelite]

again, i suggested these points before any knowledge from the Stardust press release.<br /><br />directly from my post:<br /><font color="yellow"> comets may form extrasolar-wise and then become captured by solar systems. comets may or may not form within a solar system. they could or they could not; both ways may occur, however. some comets with very long periods may have never visited the earth's sun before, and may never again, failing to enter capture of the sun and onto a trajectory to oblivion. others become trapped and stay forever. some dive headlong into the sun, into a fiery death. <br /></font><br /><br />and this:<br /><font color="yellow">the weird crystals in question could possibly be extrasolar in origin. it is currently impossible to know this, but it may be true. provided the immensity of the dust lane structures, there may be millions of crystalline structural variants that will go unknown forever. we just happened to get lucky and find these specific ones. and they may never be found again, or they may be common to the extrasolar environment." </font><br /><br />i am not ignoring your pacific ocean parallel, by the way. i do "get it." certainly, i am not certain at all how comets actually come into being. <i>i am suggesting possible ways that involve extrasolar, even pan-galactic, origin. and these ideas may actually hold promise. look at the recent press release. it is shocking and very exciting.</i>

 

[skyeagle409]

Interesting! <br /><br />I had NASA place my name on the Stardust spacecraft.

 

[bonzelite]

here is another post from the locked thread:<br />link here<br /><font color="yellow">the stratification, if you will, from terrestrial/rocky planets in the inner solar system, out past the asteroid belt to jupiter and the outer gas giants, with their icy moons, is not unknown to me, certainly. it's pretty clear a trend. <br /><br />and my schtick here is that comets may not be predicated upon this trend whatsoever. i'm throwing out a hypothesis that they may be extrasolar in origin, if not wholly, then partly. regions of comet birth may not be in any way known. regions of the solar system may render unaccreted matter or anomalous ionized particles that are heretofore unknown. i am saying that there may be stuff that "should not be there," to use a common and trite press release protectionary phrase. <br /><br />commonly known core accretion theory is already disproven as there are extrasolar gas supergiants orbiting their primary star at a distance so close to the star that the planet is nearly touching the sun's surface. so that immediately disqualifies the orderly fashion of rocky-to-gaseous-volatile as a linear axiom of development. our solar system is not the template. volatile bodies can exist near the sun, with terrestrial bodies residing farther out. and comets may indicate that terrestrial matter can exist far beyond what is assumed to be possible. indeed, comets possess a volatile component. that is undeniable and proven. <br /><br />likewise, comets may not follow a coherent or neat and tidy scheme of development under the assumptions that exclude distant terrestrial bodies. especially when what is largely observed of them thus far are quasi-asteroidal nuclei with a percentage of volatiles that stream off the coma when impinged upon by the solar plasma. <br /><br />i know you are loathe to let go of you</font>

 

[TheShadow]

bonzelite claims: <i> yeah. i was suggesting in the weird crystals thread that comets may be of extrasolar origin. and guess what? certain mods didn't like my ideas and guess what? they locked the thread. my idea was "irrelevant." </i><br /><br />That was not the case. The thread was locked due to the refusal of some members to carry on a civil and relevant debate. Some of those members are continuing that same behavior here. If you disagree, take your disagreement to Administration or start a discussion in Suggestions Forum. Do NOT continue here.<br /><br />Fair warning. This is supposed to be a discussion about the comets, keep it that way. Off-topic comments and false accusations regarding this thread or other threads will not continue. Insinuations or accusations of inappropriate behavior detract from the SCIENCE discussion and therefore will not be allowed to continue. Such comments are NOT relevant here. If you have a point to make regarding the data, the comets, or any other relevant point relevant to the discussion, then please feel free to continue to post them.<br /><br /><font size="+2">Everyone: Stick to the Science topic. No more personal comments.</font><br /> <div class="Discussion_UserSignature"> <p> </p><p> </p><p> </p><p> </p><p><font size="1" color="#808080">Who knows what evil lurks in the hearts of men, the Shadow knows. </font></p> </div>

 

[TheShadow]

FYI, I have always maintained that at least some of the asteroids or comets that are currently part of our Solar System have come from outside our Solar System. I am not talking about the fabled Oort Cloud, which still remains to be proven to exist. I believe that it is possible, or even probable that some interstellar bodies have entered, and been captured, by our Sun.<br /><br />I my discussions regarding the tracking and possible destruction/redirecting of potential Earth Impactors, I have pointed out the necessity of placing early warning sensors out past the orbit of Mars specifically to deal with the possibility of extra-solar, and therefore previously uncharted, bodies approaching Earth. Since the plane of the ecliptic is very close to the plane of the Galaxy, it is probable that extra-solar bodies would approach in the plane of the ecliptic.<br /><br />Having said that, there will may be no way to tell if a particular NEA or other potentially threatening body really is extra-solar. For all our conjectures regarding the composition of asteroids and comets, we may not be able to tell the difference. That makes speculation on the subject rather moot.<br /><br />Perhaps the only indicator we have at present about the composition of a comet (the whole comet, not just the surface) is that so much of the material that makes up a comet is boiled off upon its approach to the Sun. Rocky bodies do not do that for obvious reasons. Ergo, comets must be composed of a significant amount of volatiles, especially considering they may have been boiling off considerable amounts of material during thousands of passes near the Sun. After thousands of passes, we would expect that the surface would consist mostly of less volatile components, probably those components that will not boil off, such as rocky materials. In fact, as volatiles boil off over the millennium, I would fully expect the surface to be composed mostly of rocky materials, regardless of how the comet started ou <div class="Discussion_UserSignature"> <p> </p><p> </p><p> </p><p> </p><p><font size="1" color="#808080">Who knows what evil lurks in the hearts of men, the Shadow knows. </font></p> </div>

 

[exoscientist]

I'm in a similar boat as the EPH proponents in that my favorite theory continues to get short shrift. <br /> The only theory offered for the formation of the high temperature olivine is that it formed close to the Sun or another star. <br /> HOWEVER, the theory of radiogenic heating in comets early in the Solar Systems history could also explain this.<br /> This theory is controversial ONLY because it would raise the possibility of life on comets. Note though that radiogenic heating is a leading theory for the origin of the heating in the icy, comet-like world of Enceladus (they both have water jets.)<br /> Note as well the theory the olivine formed close to the Sun or a star would not explain why Kuiper belt object Quaoar apparently still has internal heating, whereas radiogenic heating WOULD explain it:<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 /><br /> - Bob Clark <div class="Discussion_UserSignature"> </div>

 

[yevaud]

<i>i am not ignoring your pacific ocean parallel, by the way. i do "get it." certainly, i am not certain at all how comets actually come into being. <b>i am suggesting possible ways that involve extrasolar, even pan-galactic, origin.</b> and these ideas may actually hold promise. look at the recent press release. it is shocking and very exciting.</i><br /><br />Well, then we do have an actual debate. Earlier, you were stating that *all* Cometary material was of Extrasolar origin, and yes, I vehemently disagree with that.<br /><br />It's not neccessary. It ignores the huge amount of material available, right here, from which comets can be derived.<br /><br />I suppose that a further point is, why *is* it neccessary for comets to be of extrasolar origin? Discounting such things as perhaps different isotope ratios, a comet is a comet is a comet - regardless of it's composition.<br /><br />It seems like a tempest in a teapot to suggest that it must have originated somewhere other than our solar system. Excepting, of course, the data we might glean from such a comet, should one be proven to be a capture. <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>

 

[robnissen]

To the extent that Bonzelite is arguing that some comets come from outside the solar system, I think the data from Stardust certainly doesn't contradict that view. To the extent he is arguing ALL comets come from outside the solar system (I don't think that is his argument), there is no evidence to support that view.<br /><br />As regards your quote "I suppose that a further point is, why *is* it neccessary for comets to be of extrasolar origin?" <br /><br />I think the answer to that was that NASA raised that very issue yesterday. <br /><br />Assuming that NASA is correct that at least some of Stardust's samples formed in high heat, there are only four possibilities under current theories:<br /><br />1. The comet formed close to the Sun and then was magically kicked out to the Oort cloud, and then eventually wondered back into the inner solar system.<br /><br />2. There was a magical high heat source in the Oort cloud and or the Kuiber Belt at some time in the past. <br /><br />3. The comet formed in the cold Oort belt and somehow since it entered the inner solar system in 1974 it magically picked up additional matter from the inner solar system that has been left over since the solar system formed, and by an amazing coincidence that recently added matter just happened to be the sample that Stardust picked up.<br /><br />4. The comet formed near another star, was booted out of that star system, ended up in the Oort cloud and eventually wondered into the inner solar system.<br /><br />I think all four of these theories are problematic (I realize that the EPH people have additional theories), but the one that seems least problematic to me, is that it formed near another star.

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>HOWEVER, the theory of radiogenic heating in comets early in the Solar Systems history could also explain this.<br />This theory is controversial ONLY because it would raise the possibility of life on comets.<p><hr /></p></p></blockquote><br /><br />Not to digress too far, but I don't think it's because it raises the possibility of life on comets. Experience shows that if you can make a good case for life possibly being on Celestial Body A, you have a much better shot at funding a mission to Celestial Body A. There's interest in finding extraterrestrial life, interest so strong it does sometimes defy science. (Expecting life on Titan is still premature, but it got Huygens funded. And man, was that worthwhile! It didn't find life, but what it did find will fascinate scientists for decades.)<br /><br />Getting back to what's going on with comets, I think the main objection to the idea of radiogenic heating is that it doesn't seem likely they'd have enough radioactive material. They're quite small, after all, and don't appear to be very dense. They also only seem to outgas significantly when they're near the Sun. At least, that seems to be the case, based on ground-based observations and the precious few images of several heavily battered nuclei. The Rosetta mission should help shed a great deal of light on that as it witnesses the evolution of a comet towards its perihelion from close up.<br /><br />I have a hunch that comets actually vary quite widely -- at least as much as main belt asteroids do. If this is the case, we should expect to see a lot of variation as we start to get this kind of really detailed information. Thus, it may be unwise to make too many sweeping assumptions about the rest of them, even if we have little choice in the absence of more information. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"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."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[siriusmre]

It should come as no surprise to anyone that I think that most, if not all, of the comets that we know were born "only" a few thousand years ago in a planetary cataclysmic event. The thinking goes this way: Because planets are charged bodies moving in the Sun's plasma envelope, they will interact electrically if they get too close to each other. At some point in the astronomically recent past--perhaps even at a time when anotomically modern humans were able to bear witness to and record the event--there was at least one such highly charged electrical interaction involving, most notably, Earth, Venus and Mars.<br /><br />It is postulated that this electrical arcing event was responsible for excavating the colossal canyon that is <i>Valles Marineris</i> in Mars. Similar to a plasma etching process, this electrical excavation easily accelerated millions of cubic meters of the Martian surface into space in pieces as small as a mote of dust to as large as an asteroid/comet. Some of these fragments settled into stable orbits and perhaps became part of the asteroid belt. Others took on more elliptical orbits and became comets, which, because they were flung into these highly elliptical orbits, spend the bulk of their time in the outer reaches of the system, where they eventually shed charge in order to become more electrically balanced with their environment. When their orbits bring them closer to the Sun's charge, a strong voltage gradient can form between the comet and the solar plasma. All over the nucleus of the comet, electrical discharges occur, especially at the topographically highest points. These electrical discharges, where they impinge upon the surface of the comet nucleus, achieve fantastic energies and temperatures capable of transmuting matter while etching it from the surface of the comet in the form of crystalline silicates and other "weird crystals" that can only be formed at high temperatures.<br /><br />What we are seeing, the hypothesis goes, is not that c <div class="Discussion_UserSignature"> </div>

 

[jatslo]

Hi, RobNissen - You did not answer my question.<br /><br />The Encyclopedia says, "... <font color="lightyellow">A comet is a small astronomical object similar to an asteroid but composed largely of ice. Comets typically move in highly elliptical orbits, the aphelia of which may be many times more distant than Pluto's orbit. Often described as "dirty snowballs", comets are composed largely of frozen carbon dioxide, methane and water with dust and various mineral aggregates mixed in.</font> ..."<br /><br />There is *NO* variation in this analogy; they are treating comets, as if, all comets are, in fact, "Dirty Snowballs", so why is it so hard for you to get with the program? I explained statistics a few posts up, and I showed the world why we can form an hypothesis about all comets from one sample space. There are two hypothecations, in which those two are probably narrowed down from a rather large list, and NASA has a high degree of confidence that they can twiddle the hypothecations down to just one via further testing of samples from space.<br /><br />RobNissen says, "... <font color="lightblue">arguing ALL comets come from outside the solar system (I don't think that is his argument</font> .." <-- This is an argument, and if bonzelite or anyone else does not hold that position, then I will, because I can defend it right up until the hypothesis is *REJECTED* by primary evidence, which is statistical probability.<br /><br />I found several hundred dissertations, and journals related to comets, and so much more. The world will rock in more ways that I can count.

 

[exoscientist]

RobNissen said:<br /><br /><i>2. There was a magical high heat source in the Oort cloud and or the Kuiber Belt at some time in the past.</i><br /><br /> The heat source does not have to be magical. There is already a well-known and well-established heat source that could do the trick, radiogenic heating.<br /><br /><br /> Bob Clark <div class="Discussion_UserSignature"> </div>

 

[jatslo]

No definitions were found for "Radiogenic Heating" on the first initial pass, so would you care to explain this phenomena in greater detail, so that I may learn something? TY---

 

[bonzelite]

<font color="yellow"><br />Well, then we do have an actual debate. Earlier, you were stating that *all* Cometary material was of Extrasolar origin, and yes, I vehemently disagree with that. <br /></font><br /><br />for the record, i will reiterate, as it is written in my posts as hard copies, i <b>never</b> suggested <b>all</b> comets are extrasolar. i NEVER suggested that. <br /><br />alright? do you see?

 

[bonzelite]

<font color="yellow"><br />I suppose that a further point is, why *is* it neccessary for comets to be of extrasolar origin? Discounting such things as perhaps different isotope ratios, a comet is a comet is a comet - regardless of it's composition. </font><br /><br />and this brings up the THRUST of my argument -------- /><b>extrasolar origin of comets</b>---<i>not all, but many.</i> i hypothesized this idea BEFORE Stardust data was made available. and i was not lead to conclude this "just because." <br /><br />so i don't understand, then, why you doubt EVEN THAT --that some bodies that visit Sol are not borne of Sol? especially when we have the recent press releases about Stardust? what is your deal? you cannot stretch to accept that either? <br /><br />i am in a quandary about you, Yevaud. ????

 

[Saiph]

bonze: I reread your posts a near the beginning: While you didn't say that all comets were extrasolar, it's pretty easy to get that impression.<br /><br />Now, you say that isn't what you meant. Cool.<br /><br />So, lets look at what Yevaud has said: With the vast amount of material near/in the Sol system, it's really unlikely for comets to be extrasolar in origin. Note: He's not saying there are none, just that there aren't many (percentage wise).<br /><br /><br />Jatslo: I hope you aren't taking what an encyclopedia says about comets to be the final word on what astronomy has to say about comets. Encyclopedias are almost as bad as the media. They take a large field of material, and boil it down to the basics so they can fit the entry onto a page or two (or less even). <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[jatslo]

No, Sir, I am not, and I hope nobody else is either. <img src="/images/icons/wink.gif" /> I have class tonight, so I won't be of much help today, sorry. I am very excited about researching this subject matter, though. <img src="/images/icons/smile.gif" />

 

[bonzelite]

yes, Yevaud suggests the needle in the Pacific Ocean idea. the chances of it hitting land, ie, an island, are remote to nearly zero. there's not much material out in the deep cosmic abyss to congeal, accrete, or otherwise form into something. and i say that, despite the diffuse nature of the dust out there, it can and does form things perpetually. <i>maybe.</i><br /><br />i'm suggesting there may be more formation out in the farthest reaches of the galaxy, over aeons of time as comets wander, than is assumed. the dust lanes in galaxies are substantial enough to obscure the galaxy from full view. that is a lot of material out there. and electrostatically, it can attract. Yevaud then confirmed that such EM attraction that i suggested is responsible for the primary accretion process theorized to have created our solar system. this only supported, and not refuted, my guesses.<br /><br />there is talk of EPH processes to garner comets. i'm not really up on that theory too much so i cannot fully get behind it. but it could as well be a possibility. the recent findings that the crystals from the Stardust samples formed in a fiery hell give credence to EPH. to meet EPH and my idea half-way, cometary material, at least in part, may derive directly from supernovae. comets may be the offshoots or "burning cinders" leftover from stellar explosions, then ejected into frigid interstellar space for aeons, collecting more and more material throughout their journies through the dust lanes. <br /><br />what i am saying is that more comets may form "off campus" than we think. <br /><br />that's it <img src="/images/icons/wink.gif" /><br /><br />

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>It should come as no surprise to anyone that I think that most, if not all, of the comets that we know were born "only" a few thousand years ago in a planetary cataclysmic event.<p><hr /></p></p></blockquote><br /><br />I don't think all the details of the EU model are germane, but this part is. It's not neccesarily EU, either; a non-EU variant of the exploded planet hypothesis (if one exists) could also be consistent with that.<br /><br />If comets are the remains of some fragmented planet (much as was once hypothesized about the main belt asteroids, before the belt was sufficiently mapped to rule this out), then should we not expect to see strong biases in their orbital parameters? Obviously there is one bias: they all have extremely elliptical orbits. (This is practically the definition of a comet.) But this isn't enough by itself. They seem to come from all over. Obviously we need to find more comets and better map the outer solar system to really get down to the meat of this, but the fact that they don't show a strong trend in their orbits seems, to me, to make it unlikely that they could all have once been part of a single object. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"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."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>yes, Yevaud suggests the needle in the Pacific Ocean idea. the chances of it hitting land, ie, an island, are remote to nearly zero. there's not much material out in the deep cosmic abyss to congeal, accrete, or otherwise form into something. and i say that, despite the diffuse nature of the dust out there, it can and does form things perpetually. maybe. <p><hr /></p></p></blockquote><br /><br />Y'know, it occurs to me that if this were found to be the case for a lot of comets, it might have some interesting implications for cold dark matter, because that's effectively what these comets would be made of. That might be something interesting for the dark matter thread.<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>what i am saying is that more comets may form "off campus" than we think. <p><hr /></p></p></blockquote><br /><br />If we could prove that a particular comet (say, Wild 2) formed "off campus" (I like that phrase!), just imagine what that would mean for scientists! To be able to get a piece of genuine interstellar material for study.... We can seriously imagine sending spacecraft to Pluto, but not to another star system. Not yet. To have some of this material come right to us.... That would be extraordinarily precious.<br /><br />I'm not sure how you'd prove that it was extrasolar in origin, though. If scientists couldn't work that out for certain, the specimens' value would be less. Ironically, we might not be able to determine the origin of the material until we know enough that the question no longer matters so much. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"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."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[Saiph]

calli, the "dark matter" the comet would be composed of is already accounted for when people do estimates of the dust cloud mass (from which they'd originate if they're there). It also falls into the "baryonic" cold dark matter.<br /><br />So it's unfortunately been counted already... <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[exoscientist]

Jatslo, radiogenic heating is one of the proposed explanations being given for the plumes of Enceladus. It simply means the heat given off by radioactive isotopes contained within rocky bodies.<br /> There are many references on the topic on the archive NASA maintains for astronomy papers here:<br /><br />http://adsabs.harvard.edu/abstract_service.html<br /><br /> Enter in "radiogenic" and "heating" and "comet" in the abstract search box.<br /><br /> Radioactive isotopes had been found in carbonaceous meteorites. Such meteorites likely stem from comets. From the isotope abundances, scientists were able to deduce how much of the radioactive material was present early in the Solar Systems history. They found it was enough to heat the interior of comets to exceed the melting point of water.<br /><br /><br /> - Bob Clark <div class="Discussion_UserSignature"> </div>