Landslides, avalanches may be key to long-term comet activity

September 11, 2018, Planetary Science Institute
Sequence of images showing different views of the Aswan cliff collapse on Comet 67P/Churyumov–Gerasimenko. The first image shows the fracture long before it gave away on 10 July 2015. Images taken on 15 July and 26 December show the bright, pristine material exposed in the cliff collapse, which is thought to have occurred on 10 July. Although not obvious from these images, the brightness had faded by about 50% by the 26 December image, showing that much of the exposed water-ice had already sublimated by that time. The images from 2016 show different views of the new cliff top. By August 2016, much of the cliff face had returned to the average brightness of the comet. Arrows are used to mark the fracture and the exposed water-ice, and to delineate the new cliff top outline. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The release of gases through sublimation is the defining process of comets, but a new paper by Planetary Science Institute Research Scientist Jordan K. Steckloff and Senior Scientist Nalin H. Samarasinha says that periodic landslides and avalanches, known as mass wasting, may be responsible for keeping comets active over a long time.

These escaping gases loft dust off of the , forming a dust cloud visible from the Earth. This gas release can even change the of the comet. However, this process has long been expected to shut down as the ice present at the surface of the comet sublimates away, leaving a dust layer at the surface that insulates the remaining subsurface ice. It has therefore been unknown how comets remain active, rather than fade into non-active objects.

According to "The sublimative torques of Jupiter Family Comets and mass wasting events on their nuclei" in the journal Icarus, mass-wasting activity can excavate and expose buried ices to the surface of the comet , giving the comet fresh ice to sublimate. However, mass-wasting leads to a flattening of features on the surface of the comet over time, which in turn reduces the number and frequency of mass wasting events.

"Nalin and I independently developed our own models to study how sublimating gases that escape from a comet's surface generate torques that change the comet's spin state," Steckloff said. "However, our models approached this problem from two completely different perspectives: Nalin's model is based on Earth-based observations of comet light curves and observed gas sublimation rates. In contrast, my model considers how gases push on the surface of the comet as they escape, accounting for the effects of a comets' activity, shape, and topography. Despite these different perspectives, these two models must necessarily be consistent with one another if they are to accurately describing the same phenomenon."

By comparing their models, Steckloff and Samarasinha found that their models can only agree with one another if these sublimative torques originate primarily from steep, mass-wasting-prone slopes. This suggests that mass wasting events such as and are critical to maintaining sublimative activity on comets. This is an important result, as it was previously unknown how comets maintain their activity over many, many orbits.

Moreover, this mass-wasting process provides a mechanism for reactivating dormant comets. If spin state changes or other processes can trigger a mass-wasting event on a dormant comet, the resulting exposed ice can reestablish vigorous sublimative activity. This may explain how comets such as 2P/Encke remain active. Comet Encke took so long to evolve into its current orbit, that it should have long ago run out of ices to sublimate. This dynamical evolution timescale is 200 times longer than the sublimative timescale.

It has been proposed that Comet Encke was therefore dormant for the majority of this time, but this requires a mechanism for reactivating the comet. A large mass-wasting event may have been the mechanism that reactivated Encke into the active comet that we observe today.

"We were trying to understand how cometary activity would affect their rotation." said Samarasinha. "In the process, we were able to explore the long-term evolution of cometary activity and conjecture how the surface layers of short-period comets might evolve. By understanding the physical processes occurring on the surfaces and in the surface layers of comets, we can provide the overall context to accurately interpret observations of comets. An in-depth understanding of comets help us ascertain the role played by these building blocks of the giant planets in the formation of the solar system and also the various roles played by comets throughout the history of the solar system."

Explore further: Changes in comet rotation may be predicted with greater accuracy

More information: Jordan K. Steckloff et al. The sublimative torques of Jupiter Family Comets and mass wasting events on their nuclei, Icarus (2018). DOI: 10.1016/j.icarus.2018.04.031

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cantdrive85
1.8 / 5 (16) Sep 11, 2018
It's quite amusing how they resort to ad hoc explanations to explain that which doesn't fit within their guesswork.
rrwillsj
4.4 / 5 (14) Sep 11, 2018
Well cant, as opposed yo your "thundermugs of the godlings" as an explanation?

At least these scientists are attempting to develop reasoned, rational explanations based on empirical evidence of reality.

Versus your gibbering stuporstitions and pseudo-science fraud.
dsylvan
2.6 / 5 (10) Sep 11, 2018
It's quite wonderful how science, rigorously applied as above, makes guesswork productive and worthwhile.
jonesdave
4.3 / 5 (18) Sep 11, 2018
There is no guesswork here. Cliff collapses have been seen by Rosetta.

The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse
Pajola, M. et al.
https://kar.kent.ac.uk/61744/

Given that icy 'boulders' are also seen below cliffs, then it is pretty much a certainty that these collapses happen, due to thermal stress.

http://www.esa.in...asimenko

The problem with some people, is that they are so anti-science that they put fingers to keyboard before engaging brain, and stopping to do just the tiniest bit of research.
jonesdave
4.3 / 5 (16) Sep 11, 2018
And here is a paper from 2015;

Are fractured cliffs the source of cometary dust jets?
Insights from OSIRIS/Rosetta at 67P/Churyumov-Gerasimenko
Vincent, J-B. et al
https://www.aanda...9-15.pdf
cantdrive85
1.4 / 5 (10) Sep 11, 2018
The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse

The observed "pristine interior" was due to the newly reveal matter reacting to the coma/dielectric field after being exposed. These reactions would be nearly instantaneous.
Given that icy 'boulders' are also seen below cliffs, then it is pretty much a certainty that these collapses happen, due to thermal stress.

Assumptions used to jump to erroneous conclusions, right on schedule for jonesdumb.
The problem with some people,

Is they slavishly believe everything "scientists" tell them and are unable to do the tiniest bit of thinking for themselves.
cantdrive85
1.4 / 5 (9) Sep 11, 2018
Are fractured cliffs the source of cometary dust jets?
Insights from OSIRIS/Rosetta at 67P/Churyumov-Gerasimenko

This is precisely where one would expect to see the electric erosion occurring, in fact it is a prediction. It has been observed to be true on comets as well as Io.
Captain Stumpy
4.7 / 5 (13) Sep 11, 2018
@cantthink the fanatical eu acolyte
This is precisely where one would expect to see the electric erosion occurring, in fact it is a prediction
no, it isn't
it isn't considered a prediction if you make the claim after the fact

also note, there is absolutely zero published peer-reviewed journal science in any form, anywhere, that makes the prediction that your eu electric discharges form, erode or etc in any asteroid or comet

Nor has there been any published peer-reviewed journal science where "It has been observed to be true"

lastly, if anything has been "shown to be true" then it wouldn't be any singular publication

.
rossim22
1.7 / 5 (11) Sep 11, 2018
The EU predicted that erosion of the rocky comet body would likely exist at cliff walls, peaks, crater edges to form flat mesas. This was seen on Tempel 1 where the image saturation produced white-outs exactly where predicted.
If this erosion did occur, then cliff fractures and avalanches would be expected.

Now proponents of the standard model are identifying these same regions as areas with the most activity. Only they take a different angle, in that an avalanche or fracture occurs (from a variety of plausible explanations) and that in turn exposes fresh material to sublimation.

Both perspectives are good science IMO and can explain the bursts of activity. I think the mainstream has a more difficult time explaining the sustained active jets and coma than the short bursts.
jonesdave
3.5 / 5 (13) Sep 11, 2018
The observed "pristine interior" was due to the newly reveal matter reacting to the coma/dielectric field after being exposed. These reactions would be nearly instantaneous.


What a tosser! Why do you continue lying? Hmmm? What dielectric field? Show me in the literature, you fraud. And how does this field manage to make the 'boulders' show the spectroscopic signature of water ice, you ignorant tosser? Please explain. With observed science, maths, equations, chemistry, etc.

Captain Stumpy
4.3 / 5 (11) Sep 11, 2018
@rossim
The EU predicted that erosion of the rocky comet body would likely exist at
links/references to reputable peer-reviewed sources, please
If this erosion did occur, then
it would be mentioned in the prediction
Both perspectives are good science IMO
I have to disagree
if it's good science then it will be where good science can be found, and that hasn't been proven yet

in point of fact, the most that can be proven at this time is that cd et al are claiming that a prediction has been made (sans evidence) and that this article finding matches predictions (also sans evidence)

good science would link the evidence required to substantiate a claim

If you can provide said evidence, we can work from there
until then, all the "predictions" are subject to the eu history here on PO, which means they're not considered viable and will likely be immediately dismissed
jonesdave
3.5 / 5 (13) Sep 11, 2018
The EU predicted that erosion of the rocky comet body would likely exist at cliff walls, peaks, crater edges to form flat mesas. This was seen on Tempel 1 where the image saturation produced white-outs exactly where predicted.
If this erosion did occur, then cliff fractures and avalanches would be expected.

Now proponents of the standard model are identifying these same regions as areas with the most activity. Only they take a different angle, in that an avalanche or fracture occurs (from a variety of plausible explanations) and that in turn exposes fresh material to sublimation.

Both perspectives are good science IMO and can explain the bursts of activity. I think the mainstream has a more difficult time explaining the sustained active jets and coma than the short bursts.


No, one perspective is scientifically impossible. The other is backed up by observation. Ever heard of spectroscopy, woo boy? Know what a sodding magnetometer does? Stop talking sh!te.
jonesdave
3.7 / 5 (15) Sep 11, 2018
Are fractured cliffs the source of cometary dust jets?
Insights from OSIRIS/Rosetta at 67P/Churyumov-Gerasimenko

This is precisely where one would expect to see the electric erosion occurring, in fact it is a prediction. It has been observed to be true on comets as well as Io.


What electric erosion? Two years, nothing seen. Go look at the data. However, when 'boulders' fall off these cliffs, guess what the spectroscopy shows when we look at them? Ice, woo boy. The same sort that came flying out of Tempel 1 when we twatted it with an impactor. Why do you continue to lie and obfuscate on behalf of these scientifically illiterate Velikovskians? Are they paying you?
jonesdave
3.8 / 5 (13) Sep 11, 2018
The EU predicted............


A whole bunch of crap. None of which has ever come to pass. Has it Rossim? Ever.
jonesdave
3.8 / 5 (13) Sep 11, 2018
I think the mainstream has a more difficult time explaining ........


And EU impossible woo explains nothing, does it Rossim? Zilch. You don't even have a viable mechanism. Just made up garbage by the loons T & T, yes? Neither of whom know Jack about the relevant science. Do they? So, why do you believe this crap, Rossim? I can only put it down to faith. And you know what that means, don't you? Time to go make a sacrifice to the high priest, Thornhill. IQ of of a deranged badger. No scientific qualifications of any relevance, etc, etc.
What have you got, Rossim, other than faith? No science. No evidence. What is it?

I think cantthink is beyond redemption, but I get the feeling you can still be dragged back from the abyss of pseudoscientific bollocks. Choose now, Rossim, or you'll end up like cantthink.
jonesdave
3.7 / 5 (12) Sep 11, 2018
If this erosion did occur, then cliff fractures and avalanches would be expected.


And if it were electrical woo, it would be noticed. And you have no viable mechanism for any electrical woo. No evidence, no mechanism = bollocks.
On the other hand, we see cliff collapse, we see the ice left behind, and in the talus. And we even have a spacecraft sitting almost bang on top of one of these probable cliff collapses that caused an outburst. Guess what? No electric woo. Lots of dust and water vapour.
How many contotions are you going to go through to support this unscientific garbage? Surely you're better than that, Rossim. Yes?
dsylvan
4.4 / 5 (7) Sep 11, 2018
@ jonesdave

There is no guesswork here.

Maybe you misunderstood what I meant by guesswork. All science begins with hypotheses.
Captain Stumpy
5 / 5 (8) Sep 11, 2018
The EU predicted
whats the matter @rossim?

I asked for "links/references to reputable peer-reviewed sources, please" and you get pissed?
LOL

or did you get pissed because I challenged your opinion with facts?

.

what you and cd have provided are called a "Self-report or attitudinal statement"
if you were quoting a fact it would be "supported by convergent evidence"

neither of you (or any other eu acolyte) has provided links or references to a legitimate peer-reviewed source which meets the basic requirements of the scientific method
http://www.auburn...ion.html

https://en.wikipe...c_method

note: a Scientific Fact is even more restrictive and requires validation from a second unrelated source

IOW - your lack of evidence demonstrates that you're not presenting any facts at all
you're presenting an opinion based upon your interpretations
Captain Stumpy
5 / 5 (9) Sep 11, 2018
@dsylvan
Maybe you misunderstood what I meant by guesswork. All science begins with hypotheses
let me take a stab, offered IMHO:

typically, a scientific hypothesis is tightly constrained using existing scientific knowledge, so it's more than just a guess - it's an educated guess (constrained by existing knowledge)

you still need the means to control, test and predict so that you can eliminate or validate a conclusion

If you use general hand-wavey logic, like religionists, then every conclusion has the same answer: god did it

however, this doesn't allow for prediction, let alone falsification

so a scientific hypothesis is more than just the colloquial "guess" and as such, some people who tend to frequent the site take exception to the statement, especially considering the proliferation of pseudoscience and religious trolls who tend to deny validated science here on PO
cantdrive85
1 / 5 (6) Sep 11, 2018
Lots of dust and water vapour.

You seem to be convinced that the presence of "lots of dust and water vapor" somehow precludes electric discharge. It doesn't jonesdumb.
dsylvan
5 / 5 (9) Sep 11, 2018
@Captain Stumpy
Thank you--that's a good explanation and I'm in agreement.
My original remark was a parody of cantdrive's opening statement about guesswork, but I guess it went unappreciated.
cantdrive85
1 / 5 (6) Sep 11, 2018
And you have no viable mechanism for any electrical woo. No evidence, no mechanism = bollocks.

Your utter ignorance in no way justifies or proves electric discharge is not occurring.
rrwillsj
5 / 5 (6) Sep 11, 2018
Qhoa Nelly! So now the EU cranks are claiming "that not seeing the electrical discharges" must be accepted as proof that they had occurred?

Well predict me this jokesters. Set a place and time for an immediate future occurrence of your "invisible" phenomena. So we can all watch the build up of charge, the discharge and then the resulting damage.

Or take your magical thundermugs and go home and weep.
Captain Stumpy
5 / 5 (8) Sep 11, 2018
@dsylvan
Thank you
you're welcome
My original remark was a parody of cantdrive's opening statement about guesswork, but I guess it went unappreciated
I was wondering about that

Thanks for validating my hunch about it (I up-rated it)

.

Sometimes subtlety (especially humour) gets lost in the troll posts

I can appreciate it's humour now that you've clarified it, so thanks back at ya
cantdrive85
1 / 5 (5) Sep 12, 2018
"that not seeing the electrical discharges" must be accepted as proof that they had occurred

jonesdumb claiming it doesn't exist or isn't seen is just his typical wilful ignorance and/or his attempt to misrepresent the truth.
cantdrive85
1 / 5 (5) Sep 12, 2018
My original remark was a parody of cantdrive's opening statement about guesswork, but I guess it went unappreciated.

It was hardly worthy of appreciation.
jonesdave
3.8 / 5 (10) Sep 12, 2018
Lots of dust and water vapour.

You seem to be convinced that the presence of "lots of dust and water vapor" somehow precludes electric discharge. It doesn't jonesdumb.


So, where are they? Go look at the data. What caused these invisible, undetectable discharges? Where is it written up? No mechanism + no observation = woo.
jonesdave
3.8 / 5 (10) Sep 12, 2018
"that not seeing the electrical discharges" must be accepted as proof that they had occurred

jonesdumb claiming it doesn't exist or isn't seen is just his typical wilful ignorance and/or his attempt to misrepresent the truth.


What truth, woo boy? Where is it? Go look at the RPC-MAG data. Show us these discharges, otherwise, as per usual, you are just making sh1t up. Yes?
jonesdave
3.8 / 5 (10) Sep 12, 2018
And you have no viable mechanism for any electrical woo. No evidence, no mechanism = bollocks.

Your utter ignorance in no way justifies or proves electric discharge is not occurring.


My ignorance of what, dumbo? Please tell us how this invisible electric woo is occurring. What is the mechanism? Why is it impossible to detect. Proper science, based on what was observed when we look at the jets, and the instruments that looked at them. Go.
Nik_2213
4.4 / 5 (7) Sep 12, 2018
@dsylvan, please, please put a ;-) wink after such adroit quips lest they fall foul of Poe's Law.
https://rationalw...oe's_Law
rossim22
1.7 / 5 (6) Sep 12, 2018
The EU predicted
whats the matter @rossim?

I asked for "links/references to reputable peer-reviewed sources, please" and you get pissed?


Ummm... what? Who got pissed? I didn't say anything.


you're presenting an opinion based upon your interpretations


YES! That's exactly what I am presenting.

Jonesdave and yourself are so infatuated with insulting anyone who doesn't regurgitate the standard model that you overlook any credence I give to supporters and scientists of the currently accepted models.

Try not to be so bothered by people who disagree with you, even when you believe all the evidence set forth so obviously supports your view.
jonesdave
3.1 / 5 (9) Sep 12, 2018
Jonesdave and yourself are so infatuated with insulting anyone who doesn't regurgitate the standard model that you overlook any credence I give to supporters and scientists of the currently accepted models.


I'll insult people who continually show a total lack of understanding of the relevant science, but insist on telling us the 'mainstream' is wrong. I'll insult people who refuse to believe the evidence presented to them by real scientists, that back the standard model, and totally refute the loony ideas they have. I have no time for cultists. And that is what you are. No science + blind faith = religion.
Whatever EU is, it isn't science.

jonesdave
3.7 / 5 (9) Sep 12, 2018
Try not to be so bothered by people who disagree with you, even when you believe all the evidence set forth so obviously supports your view.


No, Rossim, you don't get it. This has nothing to do with 'views'. It has everything to do with a model that works, and is based on viable science, and is backed up by evidence.
On the other hand, the EC 'model' is based on mythology, with no valid science, and zero evidence.
When you can actually present a model that matches the evidence, and is written by somebody that understands the science, and points to the evidence to back up their model, then there is really very little to say, other than that the EC model is trivially falsified. And has been for some years.

Captain Stumpy
5 / 5 (3) Sep 12, 2018
@rossim
That's exactly what I am presenting
no. sorry
the latter part of your post is opinion and stated as such - but the eu has yet to actually conform to the scientific method so that really is demonstrative of your scientific literacy more than anything

the initial part of your post -"The EU predicted"- is a statement presented as factual and explained within your post, therefore it's an attempt to lend credence to the eu as scientific or factual

this is what I am specifically requesting proof of - not just of the "prediction" part, but as such a link to the model or hypothesis that supports said predictions

(hint: besides your claim of prediction, there isn't anything that predates factual information being received from MS research)

that makes your statement either:
blatantly false (or: pseudoscience, fanatically religious, etc)
an honest mistake

this was where I needed to determine your intent, which you've now shown

2Bcont'd
Captain Stumpy
5 / 5 (3) Sep 12, 2018
@rossim cont'd
Try not to be so bothered by people who disagree with you, even when you believe all the evidence set forth so obviously supports your view
1- I don't care what you believe - what I do care about is your intentionally presenting eu pseudoscience as science

that is one of the fundamental problems we have in the world today, and so long as people like you continue to present your beliefs as legitimate science then some people have to stand against you to present an argument against it

2- I don't care if you agree with me or not, either
what I do care about is science

3- the evidence is the evidence. period. full stop

My point of view is simple: accept the evidence

not your interpretation of it
not the eu claims about it
not even the article authors interpretations of the interviews of the scientists talking about it

this was the reason why I didn't rate you - I wanted to see the evidence

thank you for validating that the eu is pseudoscience
cantdrive85
1 / 5 (3) Sep 12, 2018
It has everything to do with a model that works, and is based on viable science, and is backed up by evidence.

Except the standard model of comets failed miserably.

However, here is an example that agree with electric discharge. The standard model had to resort to something "dark" and unseen to explain the unexpected energy. To claim as jonesdumb does that the discharges are "invisible electric woo" when it was directly measured shows his wilful ignorance. His religious like defense of his crank science is amusing to say the least.
https://www.iflsc...met-67p/
dsylvan
3 / 5 (2) Sep 13, 2018
@Nik_2213
@dsylvan, please, please put a ;-) wink after such adroit quips lest they fall foul of Poe's Law.
https://rationalw...oe's_Law

Thanks for the link. That's awesome!

But...

Anti-Poe's Law:

"A clear indication of the author's intent makes it more difficult, if not impossible, to express sincere parody of extremism." ;-)
Captain Stumpy
5 / 5 (1) Sep 13, 2018
Anti-Poe's Law:
shouldn't that be "Auntie" Poe's Law??

sorry - I couldn't resist

;-)
dsylvan
5 / 5 (1) Sep 13, 2018
Yup ;D
jonesdave
3.3 / 5 (7) Sep 13, 2018
It has everything to do with a model that works, and is based on viable science, and is backed up by evidence.

Except the standard model of comets failed miserably.

However, here is an example that agree with electric discharge. The standard model had to resort to something "dark" and unseen to explain the unexpected energy. To claim as jonesdumb does that the discharges are "invisible electric woo" when it was directly measured shows his wilful ignorance. His religious like defense of his crank science is amusing to say the least.
https://www.iflsc...met-67p/


Lol. The mainstream comet model is doing just fine, as shown by a two year mission recently.
And I have no idea why you would link to a story about an outburst that wasn't electrical. Dust and ice.
No electric woo. Spacecraft flew right over it. Zilch, electric-wise. Just another example of your inability to understand the science.

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