The Electric Comet theory

[Sol88]

Now, about those "rocky" comets ...


OK, so much for the "science" of the rocky electric comets. Even our old friend Sol88 admits there are no data to support the claim.

So we are left with ...

But as I have already said ...

And where does that leave us in the "comets are rocks" question?
Data favoring "rock": none.
Data favoring "not rock": lots.
Case closed, comets are not rocks.

Because the way they measure density for both asteroid and comets is about as trusty as Bernie Madoff, I mean this is how you work out an average asteroids density;

there are approximately 1 million asteroids of diameter 1 km or larger, and that together their mass is approximately 2% of the mass of the Moon. If we assume that the "average" asteroid is a sphere with diameter 10 km, then what is the average density of the "average" asteroid? Express your answer in km/m3 so you can compare it to densities you know. Based on this result, what do you think most asteroids are made of?
Hint: Pretend that 1) all asteroids are exactly the same size and density, 2) that there are 1 million of them, and 3) together they account for the quoted mass.

Solution: This is an example of the kind of estimating (Estimate usually implies a subjective and somewhat inexact judgment) astronomers do all of the time. In this case, we'll estimate the typical density of asteroids from knowledge of the mass of all of them, and a guess as to the size of a typical asteroid. We could instead measure the size and mass of each asteroid individually (though both measurements are really hard!), and then calculate a density for each one, but in most cases, we're more interested in an average value for the group than in each individual density.

So of course you

For density, we need to know that mass and volume, so let's start by calculating the mass of the "average" asteroid. We're told that the mass of all of the asteroids together is about 2% of the mass of the Moon, which you can look up in your book:

* Mass of all asteroids = 0.02 x MMoon
* = 0.02 x (734.9 x 10 kg )
* = 0.02 x 0.0123 x 5.97 x 1024 kg
* = 1.47 x 1021 kg

But we're still not done with the mass calculation, though, since we want the mass of the "average" asteroid. The value above is the total mass of all the asteroids, but if that total is made up of one million "average" asteroids, then the mass of each average asteroid must be

* mass of "average" asteroid = mass of all asteroids / 1 million
* = 1.47 x 1021 kg / 1 x 106
* = 1.47 x 1015 kg

Now let's calculate the volume of an "average" asteroid. We're told that the diameter is 10 km, which is 10,000 m. We want the radius, which is half of the diameter, or 5,000 m. So the volume is:

* volume = 4/3 x pi x radius3
* = 4/3 x pi x (5 x 103 m)3
* = 5.2 x 1011 m3

Now, the density is simply

* density = mass / volume
* = 1.47 x 1015 kg / 5.2 x 1011 m3
* = 2800 kg/m3.

This density is higher than that of water (1000 kg/m3) and less than that of iron (8000 kg/m3), and is pretty similar to that of normal everyday rock. Thus, we can conclude that asteroids are probably made of regular old rock.

So that is obviously a very accurate way for determining mass and density of asteroids but what if there where actual 4,000,000 asteroids?

How dense are they then?

Then we can move on to how they estimate (Estimate usually implies a subjective and somewhat inexact judgment) of a comets mass and density

and that's PROOF that comets and asteroids do not have the same density!

Seems the more asteroids and the more uncertain of a comets position the more or less dense they can be

The main difference between the two is the eccentricity of their respective orbits!!

Like the crackpots said

 

[Dancing David]

So, no data. Okay.

 

[Davidlpf]

So, no data. Okay.

You didn't expect any did you?

 

[Tim Thompson]

Comet Jets

Because the way they measure density for both asteroid and comets is about as trusty as Bernie Madoff, ...

Scientists use Kepler's third law + shape to measure the densities of comets + non gravitational effects (jets)

So, according to you, the mass & density estimates for comets and asteroids are all unreliable, because they rely on Kepler's Laws?

Under the EC there is no out gassing or "jets" ... As the crackpots said jets are not gas escaping under pressure.

So how do you explain ejection velocities of about 1 km/sec? Seems pretty "jetty" to me. Dust production rates can run 10,000 to 50,000 kg/sec as long as the comet is close to the sun. Does not sound like "sputtering" to me; sounds like jets & outgassing. In fact, just look at the images of Halley's Comet nucleus from the Giotto spacecraft. You can see the jets that aren't supposed to be there (according to the crackpots), "plain as day". No sign of any "machining" or "sputtering". Just jets.

You're all blown Away!

Lets talk jets, first I'll let you embarrass yourself when you try and explain to me and my simple mind what a cometary jet is?

Your mind may well be too simple, but let's give it a try.

First, the sublimation of ics produces a porous dust mantle. This mantle insulates the ices beneath the surface and (perhaps) regulates the rate of sublimation. The sublimation is believed to take place a few centimeters below the surface and the gases percolate through the porous dust layer to escape. Energy for the sublimation is transported down to the ices. This scenario is compatible with the surface temperature of around 320 K and a temperature near 215 K for the sublimating ices.

Second, the sublimation does not take place uniformly over the surface. From the example of comet Halley, it is clear that sublimation takes place only in specific areas. The observation that the jets in comet Halley are active only on the sunward side implies a thin dust crust in the active areas. The concentration of activity into specific areas provides a natural explanation for surface features and can also contribute to the development of an irregular nuclear shape. The fraction of the surface that is actively sublimating probably ranges from 100% for a new comet to about 10% for an older comet like Halley to close to zero for an extinct comet.
​

This passage is quoted from the book Introduction to Comets; John C. Brandt & Robert D. Chapman, Cambridge University Press 2004 (2nd ed.), pages 252-253.

So we see that jets make perfectly good physical sense, while "sputtering" is not consistent with observations. It is especially noteworthy that jets are active only on the sunward side, to be expected if caused by solar heating & sublimation, but hard to explain by electrical sputtering, which should be active over the whole surface.

 

[Sol88]

Data?

For the electrical explanations for jets?

FIELD-ALIGNED CURRENT GENERATION AT PLASMA
CLOUDS OR BODIES WITH PLASMA SHELLS MOVING IN
MAGNETIC FIELDS
B.G. GAVRILOV, I.M. PODGORNY and J.I. ZETZER
Institute for Dynamics of Geospheres of RAS, Moscow, 117334, Russia

FAC generation should
occur also in induced magnetospheres of celestial bodies without intrinsic
magnetic field (Venus, comets). Magnetic field lines of induced magnetospheres are connected with the interplanetary magnetic field. The electric field E = -V x B/c produced by the solar wind can be projected along magneticfield lines inside the magnetosphere. Between the magnetic field lines,which penetrate deeply into the plasma shell, the Pedersen current should close the oppositely directed FAC. The solar wind electric field can reach N 10 mV/m. The magnetic field of the induced magnetosphere can be of several tens of the interplanetary magnetic field.

What like a plasma "jet"?

EVOLUTION OF A SPIRAL JET IN THE INNER COMA OF COMET HALE-BOPP (1995 O1)
MARK R. KIDGER, MIQUEL SERRA-RICART, LUIS R. BELLOT-RUBIO, AND RICARD CASAS

We find that the jet observed in comet Hale-Bopp (1995
O1) between 1995 August 25 and September 7 shows a highly
characteristic morphology and evolution. Some aspects of this
morphology and evolution are challenging to dust-ejection
models and may be more consistent with a plasma model.

Plasma model???

Plasma Wave Observations at Comet Giacobini-Zinner FREDERICK L. SCARF 1, FERDINAND V. CORONITI 1, CHARLES F. KENNEL 1, DONALD A. GURNETT 2, WING-HUEN IP 3, and EDWARD J. SMITH 4

Electromagnetic whistlers and low-level electron plasma oscillations were also observed in this vast region that appears to be associated with heavy ion pickup.

snip

Near closest approach, the plasma wave instrument detected broadband electrostatic noise and a changing pattern of weak electron plasma oscillations that yielded a density profile for the outer layers of the cold plasma tail. Near the tail axis the plasma wave instrument also detected a nonuniform flux of dust impacts, and a preliminary profile of the Giacobini-Zinner dust distribution for micrometer-sized particles is presented.

broadband electrostatic noise?? Like a sparkgap transmitter??

Whistlers waves? Like lightning, an arc?


But yeah no DATA, so a melting snowball would be a good model!

 

[Sol88]

So, according to you, the mass & density estimates for comets and asteroids are all unreliable, because they rely on Kepler's Laws?


So how do you explain ejection velocities of about 1 km/sec? Seems pretty "jetty" to me. Dust production rates can run 10,000 to 50,000 kg/sec as long as the comet is close to the sun. Does not sound like "sputtering" to me; sounds like jets & outgassing. In fact, just look at the images of Halley's Comet nucleus from the Giotto spacecraft. You can see the jets that aren't supposed to be there (according to the crackpots), "plain as day". No sign of any "machining" or "sputtering". Just jets.

You're all blown Away!


Your mind may well be too simple, but let's give it a try.

First, the sublimation of ics produces a porous dust mantle. This mantle insulates the ices beneath the surface and (perhaps) regulates the rate of sublimation. The sublimation is believed to take place a few centimeters below the surface and the gases percolate through the porous dust layer to escape. Energy for the sublimation is transported down to the ices. This scenario is compatible with the surface temperature of around 320 K and a temperature near 215 K for the sublimating ices.

Second, the sublimation does not take place uniformly over the surface. From the example of comet Halley, it is clear that sublimation takes place only in specific areas. The observation that the jets in comet Halley are active only on the sunward side implies a thin dust crust in the active areas. The concentration of activity into specific areas provides a natural explanation for surface features and can also contribute to the development of an irregular nuclear shape. The fraction of the surface that is actively sublimating probably ranges from 100% for a new comet to about 10% for an older comet like Halley to close to zero for an extinct comet.
​

This passage is quoted from the book Introduction to Comets; John C. Brandt & Robert D. Chapman, Cambridge University Press 2004 (2nd ed.), pages 252-253.

So we see that jets make perfectly good physical sense, while "sputtering" is not consistent with observations. It is especially noteworthy that jets are active only on the sunward side, to be expected if caused by solar heating & sublimation, but hard to explain by electrical sputtering, which should be active over the whole surface.

Ummmm........Comet Wild 2 exhibits jets on light side and dark side, stark relief, and is dry. LINK

and how does the sun sublimate ice when the comet is 7.2 astronomical units (AU) from the Sun? LINK

and http://www.nature.com/nature/journal/v380/n6570/abs/380137a0.html

Nice try Tim thompson!

 

[Sol88]

easy, electric discharge!

 

[Tricky]

I've moved about half the thread to AAH for bickering and flooding (repeating the same parts of a post again and again). Against my better judgement, I'm leaving the thread open and giving you a chance to discuss without bickering. Sol88 and Reality Check, if you cannot post without insulting each other, then I suggest you simply don't post, because further bickering and flooding is likely to result in infractions.

Thank you
Tricky

Replying to this modbox in thread will be off topic  Posted By: Tricky

 

[Tim Thompson]

Comet Wild 2 & Electric Comets

Ummmm........Comet Wild 2 exhibits jets on light side and dark side, stark relief, and is dry. LINK

Ah, yes. Wikipedia, the ultimate source of science scholarship. You should try broadening your reading horizons.

Modeling the Nucleus and Jets of Comet 81P/Wild 2 Based on the Stardust Encounter Data; Sekanina, et al., Science 304(5678): 1769-1774, June 2004.
Abstract:
We interpret the nucleus properties and jet activity from the Stardust spacecraft imaging and the onboard dust monitoring system data. Triangulation of 20 jets shows that 2 emanate from the nucleus dark side and 16 emanate from sources that are on slopes where the Sun's elevation is greater than predicted from the fitted triaxial ellipsoid. Seven sources, including five in the Mayo depression, coincide with relatively bright surface spots. Fitting the imaged jets, the spikelike temporal distribution of dust impacts indicates that the spacecraft crossed thin, densely populated sheets of particulate ejecta extending from small sources on the rotating nucleus, consistent with an emission cone model.
​

Yes, Wild 2 has jets on the dark side, but only 2 out of 20. That's quite sufficient asymmetry to show that solar heating is the primary driver. Simple thermal inertia in the nucleus easily explains the dark side jets as being the ones which still have enough energy to continue outgassing. And note that 16 out of 20 emanate from areas where insolation is maximized, once again showing that solar power dominates jet activity, not "sputtering".

Water Production of Comets 2P/Encke and 81P/Wild 2 Derived from SWAN Observations during the 1997 Apparition; Mäkinen, et al., Icarus 152(2): 268-274, August 2001
Abstract:
The water production rates of comets 2P/Encke and 81P/Wild 2 during their 1997 apparitions have been estimated from Lyman-α observations of the SWAN instrument and compared to previously published values. 2P/Encke was detected 28 times from few days preperihelion to 1.4 AU postperihelion with a perihelion water production rate Q_H2O of 2×10²⁸ s^-1. This is the first observation of perihelion Q_H2O of comet Encke. 81P/Wild 2 was detected 56 times from 1.64 AU preperihelion to 1.74 AU postperihelion with a perihelion Q_H2O of 1.3×10²⁸ s^-1.
​

The production rate numbers given here are in molecules/second. So "dry" has to be seen in context; it does not mean "no water", it means only "less water" than other comets, lime 2P/Encke. But even still, this is not a major point. There are plenty of ices around besides water, and all of them are far less dense than rocks, and all of them sublimate and form jets. Smaller amounts of water could indicate an older comet which has already outgassed a substantial fraction of its water, or it could indicate that the comet formed in a dryer environment.

Meanwhile, we still have the question of mass, density and non-gravitational forcing to talk about. So, since you bring up comet Wild 2 ...

Non-gravitational force modeling of Comet 81P/Wild 2. I. A nucleus bulk density estimate; Davidsson & Gutiérrez, Icarus 180(1): 224-242, January 2006.
Abstract:
The nucleus of Comet 81P/Wild 2 is modeled by assuming various smooth triaxial ellipsoidal or irregular body shapes, having different rotational periods, spin axis orientations, and thermophysical properties. For these model nuclei, a large number of surface activity patterns (e.g., maps of active and inactive areas) are studied, and in each case the resulting water production rate and non-gravitational force vector versus time are calculated. By requiring that the model nuclei simultaneously reproduce certain properties of the empirical water production curve and non-gravitational changes of the orbit (focusing on changes of the orbital period and in the longitude of perihelion), constraints are placed on several properties of the nucleus. The simulations suggest that the mass of Comet 81P/Wild 2 is M≲2.3×10¹³ kg, resulting in a rather low bulk density, ρ_bulk≲600-800 kg/m³ (depending on the assumed nucleus volume), and that the nucleus rotation is prograde rather than retrograde. The active area fraction is difficult to constrain, but at most 60% of the nucleus is likely to have near-surface ice.
​

The mass is determined dynamically (you did not tell us why you think Kepler's Laws are unreliable), and last I heard, density was still mass/volume. The bulk density of Wild 2 is 0.6 to 0.8 gm/cm³, less than the density of water ice. Whatever the nucleus is, it certainly is not "rock", so if we have to choose between "ice" and "rock", "ice" wins every time.

Non-gravitational force modeling of Comet 81P/Wild 2. II. Rotational evolution; Gutiérrez & Davidsson, Icarus 191(2): 651-664, November 2007
Abstract:
In this paper, we have studied both the dynamical and the rotational evolution of an 81P/Wild 2-like comet under the effects of the outgassing-induced force and torque. The main aim is to study if it is possible to reproduce the non-gravitational orbital changes observed in this comet, and to establish the likely evolution of both orbital and rotational parameters. To perform this study, a simple thermophysical model has been used to estimate the torque acting on the nucleus. Once the torque is calculated, Euler equations are solved numerically considering a nucleus mass directly estimated from the changes in the orbital elements (as determined from astrometry). According to these simulations, when the water production rate and changes in orbital parameters for 1997, as well as observational rotational parameters for 2004 are imposed as constraints, the change in the orbital period of 81P/Wild 2, ΔP=P˙, will decrease so that P¨=‑5 to ‑1 min/orbit², which is similar to the actual tendency observed from 1988 up to 1997. This nearly constant decreasing can be explained as due to a slight drift of the spin axis orientation towards larger ecliptic longitudes. After studying the possible spin axis orientations proposed for 1997, simulations suggest that the spin obliquity and argument (I,Φ)=(56°,167°) is the most likely. As for rotational evolution, changes per orbit smaller than 10% of the actual spin velocity are probable, while the most likely value corresponds to a change between 2 and 7% of the spin velocity. Equally, net changes in the spin axis orientation of 4° 8° per orbit are highly expected.
​

This is significant because sputtering does not push, but jets do. If we were seeing sputtering or "machining", we would not see a significant dynamic reaction from the nucleus. But in fact we do see the nucleus pushed & torqued. And that is exactly what we expect from jets; they act like little rockets and push the nucleus. We see here that the observed jets and the observed pushing are mutually compatible.

In all cases the standard model works very well, but the alternate "electric" explanation is not compatible with the observed behavior of the comets.

and how does the sun sublimate ice when the comet is 7.2 astronomical units (AU) from the Sun?

Is that the best you can do, 7.2 AU. I can beat that ...

Cometary Activity at 25.7 AU: Hale-Bopp 11 Years after Perihelion; Szabó, Kiss & Sárneczky, Astrophysical Journal 677(2): L121-L124, April 2008
Abstract:
Eleven years after its perihelion, comet C/1995 O1 (Hale-Bopp) is still active. Between 2007 October 20 and 22, we detected a diffuse coma of 180 × 10³ km in diameter with a slight elongation toward the north-south direction. The integrated brightness was 20.04 mag in RC, implying Afρ=300 m and albedo × dust surface aRC=4300 km². The coma was relatively red at V-R=0.66 mag, which is consistent with that of the dust in other comets. The observed properties and the overall fading in brightness between 10 and 26 AU follow the predicted behavior of CO-driven activity. This is the most distant cometary activity ever observed.
​

Note from above: The observed properties and the overall fading in brightness between 10 and 26 AU follow the predicted behavior of CO-driven activity. As explained in the paper, cometary activity at large distances from the sun is dominated by sublimation of CO ice, as opposed to water ice (which stops sublimating at about 3 AU). As also explained in the paper, the observed activity of Hale-Bopp at 25.7 AU from the Sun is completely consistent with model based predictions published in 2002 for CO driven activity.

So what we see is that none of the issues raised so far are critical problems for the standard model of comets; the answers might not be perfect, but the physical picture is completely self consistent and completely consistent with observation. On the other hand, the "electric" explanation has major problems, and is easily inferior to the standard. The "electric" model cannot explain the forces applied to cometary nuclei by jets, and the "electric" model makes predictions for jet distribution over the surface of the comet which are contradicted by observation (jets are strongly correlated with insolation). The "electric" model cannot explain any of the narrow line X-ray emission from comets, whereas the standard model not only explains, but in fact requires such emission. And of course, the "electric" model is not even self consistent to begin with, as there is no energy source available to drive it in the first place.

Standard model wins big, electric model loses big. Nice try, Sol88

 

[Reality Check]

Another interesting paper on comets (since we seem to have abandoned the electric comet idea):
Cometary masses derived from non-gravitational forces

We compute masses and densities for ten periodic comets with known sizes: 1P/Halley, 2P/Encke, 6P/d'Arrest, 9P/Tempel 1, 10P/Tempel 2, 19P/Borrelly, 22P/Kopff, 46P/Wirtanen, 67P/Churyumov-Gerasimenko and 81P/Wild 2. The method follows the one developed by Rickman and colleagues (Rickman 1986, 1989; Rickman et al. 1987), which is based on the gas production curve and on the change in the orbital period due to the non-gravitational force. The gas production curve is inferred from the visual lightcurve. We found that the computed masses cover more than three orders of magnitude: ~(0.3 - 400)*10^12 kg. The computed densities are in all cases very low (<= 0.8 g cm^-3), with an average value of 0.4 g cm^-3, in agreement with previous results and models of the cometary nucleus depicting it as a very porous object. The computed comet densities turn out to be the lowest among the different populations of solar system minor bodies, in particular as compared to those of near-Earth asteroids (NEAs). We conclude that the model applied in this work, in spite of its simplicity (as compared to more sophisticated thermophysical models applied to very few comets), is useful for a statistical approach to the mean density of the cometary nuclei. However, we cannot assess from this simple model if there is a real dispersion among the bulk densities of comets that could tell us about differences in physical structure (porosity) and/or chemical composition.

(emphasis added)

and a nice set of lecture notes: Six Hot Topics in Planetary Astronomy

Six hot topics in modern planetary astronomy are described: 1) lightcurves and densities of small bodies 2) colors of Kuiper belt objects and the distribution of the ultrared matter 3) spectroscopy and the crystallinity of ice in the outer Solar system 4) irregular satellites of the giant planets 5) the Main Belt Comets and 6) comets and meteor stream parents.

 

[Sol88]

Great explanation Tim Thompson!

Now perhaps you could clear up my misconception on why there was electrostatic noise and whistlers observed by ICE?

 

[Sol88]

Yes, Wild 2 has jets on the dark side, but only 2 out of 20. That's quite sufficient asymmetry to show that solar heating is the primary driver. Simple thermal inertia in the nucleus easily explains the dark side jets as being the ones which still have enough energy to continue outgassing. And note that 16 out of 20 emanate from areas where insolation is maximized, once again showing that solar power dominates jet activity, not "sputtering".

Ohh ok so we can have jets anywhere? Ok, so it does not matter if they come from the dark side or sunlit side, though your theory said only from the sunlit side!

Second, the sublimation does not take place uniformly over the surface. From the example of comet Halley, it is clear that sublimation takes place only in specific areas. The observation that the jets in comet Halley are active only on the sunward side implies a thin dust crust in the active areas. The concentration of activity into specific areas provides a natural explanation for surface features and can also contribute to the development of an irregular nuclear shape. The fraction of the surface that is actively sublimating probably ranges from 100% for a new comet to about 10% for an older comet like Halley to close to zero for an extinct comet.

we'll do the CO2 thing next! but can you please provide a link to the paper on CO2 sublimation at 25 AU.

Thanks

 

[Sol88]

Sol88
Have you noticed that some idiot () started a thread on the electric comet idea, is now ignoring the actual electric comet idea and displaying their ignorance of the standard comet model by asking off-topic questions?

What this means is that this ignorant person has abandoned the electric comet idea since they can not produce any real evidence for it, e.g. measured comet densities that are comparable to rocks or an actual X-ray spectrum for the "electric discharges".

Instead this person is reduced to asking questions about non-electric comet concepts. They are obviously deluded into thnking that by displaying their ignoroance of standard comet theory that they will impress lurkers. They are wrong. They are just making a laughing stock of themselves and the electric comet idea.

EPIC FAIL Sol88 YET AGAIN


When are you going to get back to the electric comet model - or have you abandoned it as the non-science woo that it is?

No I have not, please explain the standard mainstream explanation for the observed highly collimated jets!

I ask not thru my lack of understanding the standard model, but so you and Tim stop moving the goal posts!

Remember consistency!

 

[Sol88]

First, the sublimation of ics produces a porous dust mantle. This mantle insulates the ices beneath the surface and (perhaps) regulates the rate of sublimation. The sublimation is believed to take place a few centimeters below the surface and the gases percolate through the porous dust layer to escape. Energy for the sublimation is transported down to the ices. This scenario is compatible with the surface temperature of around 320 K and a temperature near 215 K for the sublimating ices.

That's not what Deep impact found was it Tim? How far below the surface did they find your ice?

Moreover, it is significant that the extent
of this ice on Tempel 1’s surface is not sufficient to produce
the abundance of water flux observed in the comet’s coma. The
Deep Impact team concludes that ‘‘there are sources of water
from beneath the comet’s surface that supply the cometary coma
as well.’’

LINK

And your highly porous dust layer should be one of the greatest insulators we know of bar maybe aerogel!

And if that is the case then how is the heat "transported" down?

The passage of thermal energy through an insulating material occurs via three mechanisms: solid conductivity, gaseous convection, and radiative (infrared) transmission. The sum of these three components gives the total thermal conductivity of the material. Solid conductivity is an intrinsic property of a specific material.

Highly porous bulk or solid materials such as Aerogels (and comets) are remarkable thermal insulators because they almost nullify the three methods of heat transfer (convection, conduction, and radiation). For dense silica, solid conductivity is relatively high. However, silica aerogels and other highly porous silica based materials possess a very small fraction of solid silica. The solids that are present consist of very small particles linked in a three-dimensional network. Therefore, thermal transport through the solid portion of silica aerogel and these types of materials occurs through a very tortuous path and is not particularly effective

Added comets.

also

Tim said

Yes, Wild 2 has jets on the dark side, but only 2 out of 20. That's quite sufficient asymmetry to show that solar heating is the primary driver. Simple thermal inertia in the nucleus easily explains the dark side jets as being the ones which still have enough energy to continue outgassing. And note that 16 out of 20 emanate from areas where insolation is maximized, once again showing that solar power dominates jet activity, not "sputtering".

Thermal inertia, sounds like a big word does'nt it Tim, had me impressed!
but......wait

this mob says differnet!

The temperature map matches the
topography of the nucleus, with the hottest areas close to the
subsolar point. This is an indication that the thermal inertia is low
(Groussin et al. 2006), probably lower than 100 J m
2 K
1 s
1/2
( hereafter these units are referred to as ‘‘MKS’’).

maybe it's just high enough (thermal inertia) to save your model, after all Yes, Wild 2 has jets on the dark side wich you do concede after stating The observation that the jets in comet Halley are active only on the sunward side implies a thin dust crust in the active areas!

and

Tim said

The fraction of the surface that is actively sublimating probably ranges from 100% for a new comet to about 10% for an older comet like Halley to close to zero for an extinct comet.

but A’Hearn et al

These regions cover
a small fraction of the surface, only 0.5% (A’Hearn et al. 2005;
Sunshine et al. 2006).

and

space. Moreover, it is significant that the extent
of this ice on Tempel 1’s surface is not sufficient to produce
the abundance of water flux observed in the comet’s coma.

So that narrows it down eh Tim? your model can now cover from A'Hearns quess of 0.5% to your 100%!!!! great science that.

 

[Reality Check]

No I have not, please explain the standard mainstream explanation for the observed highly collimated jets!

I ask not thru my lack of understanding the standard model, but so you and Tim stop moving the goal posts!

Remember consistency!

Please cite your source for "observed highly collimated jets".

But I can certainly make a guess for the source of jets that go in straightish lines. Look at the images of the surface of comets. Notice the craters and pits? A jet issuing from a crater or pit will be "collimated" by the walls of the crater or pit.

There is no moving of the goal posts. This is a thread about the electric comet idea. You should know this since you started it. We already know that the electric comet idea is invalid since 2 basic predictions have failed (density and X-rays bursts from electrical discharges). You have ignored this and are just asking questions about the standard comet model.

You have not yet been able to give any citation to papers that calculate any properties for these electrical discharges, e.g. the spectrum of the discharges or even the rate of discharges.
However I do have another thought - can you give a citation to the paper that calculates the emission of the electrical dicharges in visible light?
If these electrical discharges emit any light in the visible range then they would have been seen during the impact phase of the Deep Impact mission, especially by the camera on the impactor. As far as I can determine there are no discharges seen in the images before the impact (you may be able to correct me).

 

[Reality Check]

That's not what Deep impact found was it Tim? How far below the surface did they find your ice?

Deep Impact found ice on the surface of Tempel 1.

In a paper appearing in Science Express on Feb. 2, 2006, an article by Sunshine et al. reports on the Deep Impact science team's finding of a small area of water ice on the surface of Tempel 1. This is the first time that water ice has been observed on the surface of a comet. Past efforts with the near-IR spectrometer on Deep Space 1 mission flying past comet Borrelly and from the ground of comets far from the sun and not enshrouded with coma, have yielded no evidence of water ice on their surface.

And your highly porous dust layer should be one of the greatest insulators we know of bar maybe aerogel!

And if that is the case then how is the heat "transported" down?

Added bolding

Please cite the source for your quote.
What do they actually calculate for the thermal properties of a dusty surface for a comet?

 

[Sol88]

RC re read post 154

 

[Reality Check]

Ohh ok so we can have jets anywhere? Ok, so it does not matter if they come from the dark side or sunlit side, though your theory said only from the sunlit side!

Can you give a citaton to the paper or textbook that states that the standard comet model predicts jets only on the sunward side of comets?

Thanks.

IMHO it is fairly obvious that it is possible for jets to appear on the dark side of the a comet. The dark side is where CO is most likely to solidify. It would not take that much heating to penetrate the comet or flow along its surface to create a jet from the CO.

 

[Reality Check]

...snip...
Added comets.

In other words you just assume cometary dust is as insulating as Aerogels.
Give us a number.
ETA: Remember that insulation does not stop insulated material from heating up. It merely delays the heating. If there is an oportunity for cooling then the insulation will reduce the average temperature of the insulated material.
Comets are heated for periods of years. There is plenty of time for the heat to penetrate the dusty surface.

Tim said

Thermal inertia, sounds like a big word does'nt it Tim, had me impressed!
but......wait

this mob says differnet! maybe it's just high enough (thermal inertia) to save your model, after all Yes, Wild 2 has jets on the dark side wich you do concede after stating The observation that the jets in comet Halley are active only on the sunward side implies a thin dust crust in the active areas!

That is right. Tim stated that there was thermal interia and that mob gave stated that it was low and give a number (actual science!)

Tim said but A’Hearn et al and

So that narrows it down eh Tim? your model can now cover from A'Hearns quess of 0.5% to your 100%!!!! great science that.

Yes great science!
Comets have different ages and so they have different amounts of volitile materials.

Tim stated a range for all comets:

The fraction of the surface that is actively sublimating probably ranges from 100% for a new comet to about 10% for an older comet like Halley to close to zero for an extinct comet.

A’Hearn et al stated a value for a specific comet:

These regions cover a small fraction of the surface, only 0.5% (A’Hearn et al. 2005; Sunshine et al. 2006.

The results of A’Hearn et al suggest that Tempel 1 is a very old comet.

 

[Sol88]

Please cite your source for "observed highly collimated jets".

But I can certainly make a guess for the source of jets that go in straightish lines. Look at the images of the surface of comets. Notice the craters and pits? A jet issuing from a crater or pit will be "collimated" by the walls of the crater or pit.

There is no moving of the goal posts. This is a thread about the electric comet idea. You should know this since you started it.

You have not yet been able to give any citation to papers that calculate any properties for these electrical discharges, e.g. the spectrum of the discharges or even the rate of discharges.
However I do have another thought - can you give a citation to the paper that calculates the emission of the electrical dicharges in visible light?
If these electrical discharges emit any light in the visible range then they would have been seen during the impact phase of the Deep Impact mission, especially by the camera on the impactor. As far as I can determine there are no discharges seen in the images before the impact (you may be able to correct me).

The jet is seen to have a three-part structure: there is an initial narrow straight jet of material ∼7&arcsec; long and gradually increasing with date, leaving the nucleus in P.A. ∼ 280°. This straight section appears to be highly collimated and has negligible curvature. This we refer to as “the collimated jet.” This section abruptly changes direction by 90° and opens out at a comparatively narrow opening angle before starting to sweep round to the east and opening out further. Similar behavior was reported by West (1995), who also observed the jet on several nights, confirming the position angle of the collimated jet and its constancy.

LINK

RC said

jets that go in straightish lines.

maybe you missed the highly collimated and has negligible curvature, and not straightish lines!!! Then they turn thru a right angle??? how do your craters do that!

We already know that the electric comet idea is invalid since 2 basic predictions have failed (density and X-rays bursts from electrical discharges). You have ignored this and are just asking questions about the standard comet model.

One of those queses (density) relies on outgassing which is fictitious!

'cos from the same link

We have been struck by the peculiar morphology of the August jet event, some aspects of which appear more consistent with a plasma event than with pure dust emission. The jet shows a very narrow, highly collimated section that expands away from the nucleus. This shows a 90° break at a projected distance initially of 23,000 km, at which point the material directs itself very precisely in the antisolar direction. This could be due to a chance alignment, and it is also consistent with a plasma-jet model. The ejected material proceeds outward until it reaches the contact surface and is open to the influence of the solar wind. At this point, solar wind pickup occurs and the position angle is abruptly changed as it sweeps round the contact surface until it reaches a position angle corresponding to the antisolar direction. The fact that the end of the jet was very closely aligned with the antisolar direction 2 favors a plasma model.

ETA (again) whats the plasma model Reality check???