How bright? How bright was it expected to be (in the EU model)?

How was the brightness expected to vary, by time, in the EU idea?

How bright? How bright was it expected to be (in the EU model)?

How was the brightness expected to vary, by time, in the EU idea? [/b][/quote]
Hi Nereid

In this "handwaving phase" of the EU ideas there is not much to calculate.

1 In the EU model an electrical discharge was expected in addition to the impact energy.
2 Several (all?) scientists at nasa were surprised that the flash was much brighter than they expected. They expected to see just the impact energy.

If I put 1 and 2 together it seems EU still stands.

gerards regards

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The EU proponents WERE saying that the comet nucleus was made of stone, and that the crater would be narrow and deep with fairly small amounts of ejecta, and that the ejecta would be in a columated jet.

What we saw was consistant with the idea that the comet surface material is very porous and made of ices.

Now, personally, I never understood why the EU guys thought that it mattered to them what the nucleus was made of, but clearly it wasn't made the way they thought it was. I assume that they will now embrace something close to what the main-stream view of the chemistry of the comet surface.

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The EU proponents WERE saying that the comet nucleus was made of stone, and that the crater would be narrow and deep with fairly small amounts of ejecta, and that the ejecta would be in a columated jet.

What we saw was consistant with the idea that the comet surface material is very porous and made of ices.

Now, personally, I never understood why the EU guys thought that it mattered to them what the nucleus was made of, but clearly it wasn't made the way they thought it was. I assume that they will now embrace something close to what the main-stream view of the chemistry of the comet surface. [/b][/quote]
The surface can't be made of fluffy material, because (as on comet Wild2) there is clear evidence of relief. You mention evidence of ices, what evidence? There is a report on OH molecules, but that's not a distinction between the models, and no evidence of large amounts of ices, necessary to fuel the jets. About the crater size and shape there is nothing definitive available yet, but a narrow cone is consistent with EU predictions.

Don't forget to mention the bright spots, also expected in the EU view.

The reason EU guys mention what the make-up of comets are is the notion they are the same material as asteroids, the only difference is their orbit with regards to the Sun (actually the electric field centered on the Sun). And if comets are made of stone, they produce their jets by a mechanism different from the heating of subsurface ices through a black layer (which is improbable in itself) , namely EDM. If it can be shown that comets don't contain large amounts of ices, it will practically prove the EU model, unless you can think of other ways to produce dust and jets?

Oh, and the initial burst of light was expected in the EU model, nobody else even considered this.

Cheers.

What!?!

I wrote that there would be an initial burst of light (including low-energy xrays) from the heat of stopping the impactor. This idea was not original to me. It is not honest to say no one else thought there would be a burst of light as the thing hit. Every model of this thing said there'd be a burst of light. The existance of the light does not advocate the EU model over any other (including the anti-matter comets idea). The nature of the light might. We'll have to see that that says.

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XMM Newton detected water in the ejecta. According to this article in Astrobiology Magazine the results So, per the early data, Tempel 1 is an icy comet with an upper crust.

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Thanks for the link John L,

The article is confusing (to me at least), because it isn't obvious what they are showing and how they reach their conclusions. If I understand correctly there is a lot of dust, indicating a hard surface, plus there are OH molecules that increase up to 4.5 hours and then decrease again. The OH is thought to arise from vaporised ices (why only OH, wouldn't H2O be stable?), which in the EU view is thought to arise from Oxygen ions recombining with protons which are already present in the surrounding cloud. No mention of the other ices (methane, ammonia etc), likely those are measured with different instruments.
I recall that in other comets no evidence of those molecules were found down to the limit of detection (I'll try to find the reference). So, if the OH production stops after a few hours, why would the dust production continue for a longer time? I would expect it to be in reverse order, but maybe I am too confused, or didn't understand the article correctly.

Cheers.

What!?!

I wrote that there would be an initial burst of light (including low-energy xrays) from the heat of stopping the impactor. This idea was not original to me. It is not honest to say no one else thought there would be a burst of light as the thing hit. Every model of this thing said there'd be a burst of light. The existance of the light does not advocate the EU model over any other (including the anti-matter comets idea). The nature of the light might. We'll have to see that that says. [/b][/quote]
You're right Antoniseb,

I apologise for the remark, it seems the facts are explained in this part of the Planetary Society article I linked to previously

Depending on the "signature" of the flare it won't tell if the EU view is correct, but that will have to wait for additional data.

Cheers.

What ultraviolet photons would water give off? Certainly the water ice closest to the impact would have been heated to a high enough temperature to break at least one of the bonds.

What says that the dust had to come from a hard surface? It could have been embedded in the icy structure the same way that dust is embedded in snowbanks here on Earth.

Some of these issues will be resolved when a quantitative analysis of the various spectral observations are made in all frequency ranges. We should be able to figure out how much material was ejected from the comet, taking how much energy as it left. We should be able to determine the total mass observed of several types of ions, and be able to subtract that and make assumptions about the rest (assumptions that will probably stand until the Rosetta probe gets where IT is going).

You are right that it will be interesting to see the time signiture on what happened to the various things we can detect over time.

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The exact timing of the event can tell a lot. A high-speed image sequence was mentioned on this page

Does anyone know whether the complete sequence is published somewhere?
The 8-frame sequence that is available, looks incomplete.

I calculated the distance the impactor travelled per frame of 0.05 sec. At 514 m/frame a "few" frames can be as much as 1.5 km. That is a relatively thick layer on a muffin 10 km wide.

The alternative is a flash at some distance above the surface, before the actual hit.

gerards kind regards

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APOD has a nice pic for today.

also...they report "a relatively narrow plume of debris "

Antoniseb, thermal X-rays are not what we are looking for, according to this article there are two mechanisms mentioned that explain why comets emit X-rays and none of them is thermal. Interactions between comet particles with solar wind ions is one mechanism (which is in a roundabout way comparable to what the EU model says, only without mentioning that moving charged particles are also known as currents), the other is reflection of solar X-rays. So, even if we do see thermal X-rays, it is not the normal way of X-ray production. Comet Tempel 1 seems to be a weak X-ray source, not unsurprising because it is a short period comet with a relatively low activity.

The problem with this low activity, according to the XMM Newton scientists, is that it will be difficult to get a spectrum, if at all. Hopefully there will be enough X-rays to show the signature of the event, fingers crossed. Btw, they explain in the article that they need to convert the X-rays to a virtual source because the camera apparently doesn't "track" and also they need to subtract background events, I hope this won't influence sensitivity.

Cheers.

For these two mechanisms, you are omitting discussion of comets being struck by 370 kg copper ingots travelling at a relative 10 kps. THESE comets should have a third xray source for a brief flash.

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Ok, I looked at the movie again and (after the short flash and after the pause), when the larger flash starts you can see that a large area brightens on the comet's surface, and even a second area, to the upper right of the initial area, starts brightening as well. This means that the impact triggered a very large effect, I think it is now crucial to see the impact site, and try to understand how such a large area can be affected from the impact site. I think that in EU terms, a simultaneous emission of dust over a large area is easy to explain, if you look at the close-up of the target area a large number of bright spots (sites of electric arcs) are already in place just waiting for a "conducting" disturbance to facilitate the EDM process.

Cheers.

Which movie are you looking at? the HRI movie or the MRI movie. From what I've seen the MRI movie is showing me more, including some interesting information by looking at the shadow of the plume, which shows us the plume & crater diameter.
http://www.nasa.gov/mov/121527main_MRI_impact.mov

I do NOT see what you're talking about with a second area brightening to the upper right in either movie. I also do not see lots of bright spots from electric arcs. Can you capture a frame and annotate it?

Another thing worth noting is that neither of these movies have a frame right high enough to justify the 50 millisecond or less claim about the flash. That must have come from another instrument somewhere. In the MRI movie, there is a two frame flash saturating the CCD. This can't both be from that very short flash, and must be a milder longer duration flash.

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Here is the sequence of images taken from the movie


Maybe this clarifies what I said earlier.

Cheers.

Here is an image of the probe's onboard camera with the close-up of the target area showing a large number of bright spots. These spots are also visible in images of the Stardust mission to comet Wild-2 if you recall.

Cheers.

Antoniseb earlier:
The UT news of Swift's UV measurements tells us Deep Impact hit a hard surface, and not a soft, snowy one. So, high amounts of dust and the UV signature, and the visible high relief of Tempel1's surface all indicate a hard surface, exactly what the EU proponents predicted.

They decided to use UV to detect water, isn't there any way to distinguish between OH formed by Oxygen ions recombining with protons, instead of H2O degraded by radiation? Or maybe water ice can be detected directly?

Cheers.

The Swift observation could be explained by no UV as it crushed through a light very porous crust, and then slammed into a hard inner surface, causing the flash.

Water ice cannot be directly detected by UV emissions. Also, if the EU claim is that the Oxygen was liberated from the stony materials at the time of impact, where are the metals that would have been liberated at the same time (Al, Si, Fe, Mg, Ti, etc.) They should have been observed in equal quantity to the Oxygen, but were nowhere to be seen.

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Aren't we straying away from examining the EU idea?

As I understand it, the EU idea is quite clear (= little room for ambiguity) on what the net charge of Temple-1 is, cf the Deep Impact impactor ... you simply take the published work of Jürgens, Thornhill, Scott, et al., add the (well known) parameters on the comet's orbit, turn the handle, and the answer will pop out.

Disappointingly, thnderbolts seems to have not published calculations based on the fundamentals of the EU idea.

OK; that is what it is. The only question, at the OOM level, is how much of the charge imbalance would be 'discharged' in an electric thunderbolt prior to impact ... the physical parameters of the medium in which the discharge (EU idea) occurs could have been estimated (to an OOM) before DI was even launched, and post-impact, can be nailed down to (possibly) the 10% level.

Does anyone know why Thornhill, Scott, Peratt et al. didn't publish such OOM calculations (after all, taking them at their word re their formal education and mastery of Alfvén's plasma physics, such calculations would have taken no more than a weekend)?

You keep implying these calculations are easy, if so why don't you show why the calculations won't work (after all you think EU is all bogus anyway).
What is the strength of the radial electric field?
What is the variation of the electric field?
How much charge can a comet "carry"?
What is the composition of a comet?
What is the density and composition of the plasma surrounding the comet?
How much does the "solar wind" influence these parameters?

All kinds of questions that can't be simply answered, and what is wrong with the qualitative approach anyway, bright spots hovering above the surface of comets exactly where jets are active can't be simply put into a formula. There will be lots of data soon, let's not try to get into the puny details when we first have to show that these bright spots are electric arcs, emitting UV and possibly X-rays. I think it is always better to use data/observations and then work back towards a model.

Cheers.

I'm leaving for a long vacation, and will likely be incommunicado for the rest of July. I have not been keeping track of Deep Impact news, trying to get my own work in order. However, I will make a few comments, and leave the rest of you to it.

You all know already what I think of the "EU", and my thoughts have not been altered by anything related to Deep Impact. The bright spots mentioned by VanderL are all facing the sun and easily explained as sunlight reflecting from appropriately angled surfaces. As for the impact itself, so much of it as I have seen, there is nothing that is indicative of an EU explanation. The hard surface, for instance, is an expectation from standard theory. The fact that the flash was "brighter than expected" is hardly indicative of anything except what it says. The light we see comes either from the immediate impact itself, or from sunlight shining on a plume of dust (& gas). There is nothing indicative of an "electric" glow, nothing indicative of "electricty" at all, so far as I can see.

It is as expected. The EU is so vaguely defined that it is quite impossible to carry out any experiment, of any kind, on any object, the results of which cannot be readily explained (always after the fact) by the EU. That alone makes it a worse than uselss idea.

So long for now.

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Hi VanderL

I'm quite sure you mean either "not surprising" or "unsurprising"

regards

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The Swift observation could be explained by no UV as it crushed through a light very porous crust, and then slammed into a hard inner surface, causing the flash.[/b][/quote]
What happened to the "dirty snowball with tarry outside"? That was my favourite mainstream model. The one I could understand being formed in billions of years.

Now we have a solid frozen inside with a thick fluffy crust. And the top of this crust hard enough to acount for the pre-flash.
:blink:

gerards regards

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Es gibt keine Tatsachen, es gibt nur Interpretationen. (There are no facts, only interpretations.) Friedrich Wilhelm Nietzsche

Hi VanderL

I'm quite sure you mean either "not surprising" or "unsurprising"

regards [/b][/quote]
Yep,
Thanks,

Cheers.

Hi Tim,

No, you're dead wrong on this, first of all, some of the bright spots on Wild 2 throw a shadow, second, some of those on Wild-2 face away from the Sunside, several are inside a crater. It was specifically excluded to be reflection in that case.
On Tempel 1 we don't have imaging of the dark side and some may be sunlit, but the fact they are there at all means something fundamental, both close-up views of comets show these strange spots.
And on Wild2 the spots were associated to the jets, exactly what electric arcs would be doing.

The EU expected a short flash, followed by a brighter flash, plus they expected (at least) a second site of brightening. The hard surface was not expected in the standard view, there are still many that talk about the surface being fluffy, because a lot of dust was kicked up. Downplaying the brightness is disingeneous at the least. If it was expected, the NASA people wouldn't have taken this long to show us the impact site, the brightness made it very difficult to see the impact site itself.

It is obvious as well that the standard view never made any predictions at all (aside from a crater size between 10 en several hundred meters), and so far the predictions did support the EU view, I suspect you didn't even check the EU predictions.

Cheers.

Here is an article where bright spots are linked to jets, and where jets are seen emitting from the dark side.

Cheers.

I also liked the "dirty snowball with tarry outside". This still seems about right, except perhaps that comets that have been through the inner Solar System for a while there is a thin crunchy structure of the less volatile ices capabel of holding up the tarry surface for the outermost layer... I've seen nothing official yet, so expect some details to change or be refined as we go along here. The inner core would still essentially be a dirty snowball.

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Which is based on nothing but pure conjecture, it seems we are so convinced about the existance of large amounts of ice that if it isn't on the surface (that was found to be totally black), and not near the surface (Deep Impact hit a hard surface) it MUST be somewhere deeper inside. But now we get a new problem, how can the Sun's radiation penetrate a black hard surface to heat subsurface ice enough to form explosive jets as far out as the orbit of Jupiter. It's time to lay the "dirty snowball" theory to rest and think about something new.

Cheers.

Well, pure conjecture, plus the obvious high amounts of Hydroxyl ions in the plume, and the absence of heavier elements, such as Magnesium, Silicon, Aluminum, Titanium, or Iron. If the plume is made of water, what must the impactor have hit?
I don't know that 9P/Tempel 1 was jetting material as far out as Jupiter. I remember that Kohoutek and some other very long period comets did. Speculation there was that THESE comets are on their first visit to the inner solar system, and so have a thin tarry surface and ices with a much lower boiling point - frozen molecular Hydrogen perhaps? (my speculation, not from any paper I've read).

After a few turns around the inner solar system, the easily vaporized materials should exist only deep within the comet nucleus, and would come out only if the long term average temperature of the comet increased.

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