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Rosetta arrives at comet destination

comets churyumov–gerasimenko rosetta philae esa

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#46    bison

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Posted 11 August 2014 - 03:15 PM

View Posttaniwha, on 11 August 2014 - 08:09 AM, said:

Theres got to be well over 200 craters on its surface.  Thats one tough rock!
Yes, assuming that all those features that appear to be craters actually are such, this object seems remarkably durable. The density of the comet has been given as about one tenth that of water, or about the consistency of fresh snow.
One tends to think that any sizable impact would break the object apart. In that case, some of the material might eventually merge again via gravitational attraction, but structures like craters would very probably be erased.
Since this has not occurred, the question remains--why not?
It's been suggested that the comet could have been larger and denser when the craters were formed, and so, withstood the impacts.
It's also been remarked that the craters could be due to the comet expelling gas directly sublimed from its ice, rather than impacts. I'm not aware of any essentially circular areas of gas discharge in previously observed comets. It's already well known that impacts can create circular craters.
A third suggestion is that comet was impacted by other, similarly constituted objects, which limited the impact damage, due to their low mass and density.
Since the density of comet 67P/Churyumov-Gerseminko is very low in comparison to other comets, it seems unlikely that it would just happen to be struck by another comet of similar composition, especially where relatively large, rare impacts are concerned.
It also seems unlikely that gas expulsions would take the form of circles, like craters, rather than random shapes, particularly where large features are concerned.
The irregular shape of the comet suggests the possibility that it is a fragment of a larger object. Comets do sometimes break apart when they are near the Sun, due to loss of ice from heating. It appears, from the dynamical history of 67P, that it has spent the vast majority of its life, since the formation of the solar system billions of years ago, at a distance of at least 4 astronomical units from the Sun. A comet is not expected to be notably affected by the heat of the Sun at that distance, to lose much of its substance, or to be likely to break apart.

Edited by bison, 11 August 2014 - 04:09 PM.


#47    Waspie_Dwarf

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Posted 11 August 2014 - 03:30 PM

View Postbison, on 11 August 2014 - 03:15 PM, said:

One tends to think that any sizable impact would break the object apart.

As I have already pointed out that is not necessarily the case. I used the example of a block of ice and a sponge but there are many other examples I could have used.

The fact is that a porous body can be far more elastic than a non porous one, meaning it is far more capable of absorbing an impact withut breaking apart.

The one thing that is fact is that you are continuing to make guesses with no supporting data.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#48    Waspie_Dwarf

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Posted 11 August 2014 - 03:37 PM

Another newly released image:


"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#49    bison

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Posted 11 August 2014 - 05:24 PM

View PostWaspie_Dwarf, on 11 August 2014 - 03:30 PM, said:

As I have already pointed out that is not necessarily the case. I used the example of a block of ice and a sponge but there are many other examples I could have used.

The fact is that a porous body can be far more elastic than a non porous one, meaning it is far more capable of absorbing an impact withut breaking apart.

The one thing that is fact is that you are continuing to make guesses with no supporting data.
Please do suggest a porous substance that would be realistically found in a comet that would be resilient or resistant to disruption by impact, despite having a density one tenth that of water. As to speculation, or if you will, guessing. I have found the following words quite illuminating in this regard: "Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research." --Albert Einstein


#50    Waspie_Dwarf

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Posted 11 August 2014 - 05:58 PM

View Postbison, on 11 August 2014 - 05:24 PM, said:


Please do suggest a porous substance that would be realistically found in a comet that would be resilient or resistant to disruption by impact, despite having a density one tenth that of water.
I'll be honest I don't know, but neither do you. The difference is that I am not taking wild guesses, you are.

By your own admission the make up of this comet is currently unknown:

View Postbison, on 09 August 2014 - 05:09 PM, said:

so we can not say with any certainty what the condition, texture or density of any ice there might be.
Despite this you are quite happy to make post after post about features which may or may not be impact craters in an attempt to  make a story out of nothing. I asked if you were going to do the scientific thing (this is the science section after all) and wait until there was actual data. You answer is a clear no. It seems you are more interested in weaving a tall tale then discovering the truth.

View Postbison, on 11 August 2014 - 05:24 PM, said:


As to speculation, or if you will, guessing. I have found the following words quite illuminating in this regard: "Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research." --Albert Einstein
It's amazing how many people use that quote out of context when they can't back up their arguments with facts. However if you want to play the quote game it's a game two can play. Here are some other quotes for you to ponder:

Quote

A wise man, therefore, proportions his belief to the evidence.
-  David Hume

Quote

Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence.
- John Adams

Quote

What can be asserted without evidence can also be dismissed without evidence.
- Christopher Hitchens

Quote

Belief without evidence in what is told by one who speaks without knowledge, of things without parallel.
- Ambrose Bierce

Quote

Science replaces private prejudice with public, verifiable evidence.
- Richard Dawkins

Quote

It is not what the man of science believes that distinguishes him, but how and why he believes it. His beliefs are tentative, not dogmatic; they are based on evidence, not on authority or intuition.
- Betrand Russell

What I do not understand is why you are so desperate to make wild guesses about something when you can just sit back, let ESA do their work and in a few months actually KNOW something.

Edited by Waspie_Dwarf, 11 August 2014 - 06:00 PM.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#51    Waspie_Dwarf

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Posted 12 August 2014 - 09:16 PM

Today's newly released image:


"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#52    qxcontinuum

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Posted 13 August 2014 - 05:30 AM

Why exactly do we believe this is a comet and not an asteroid ? I am failing to see a comet as it should be an icy body.
Everything i see instead is a very ordinary celestial body that looks identical to a meteorite.

Edited by qxcontinuum, 13 August 2014 - 05:33 AM.


#53    toast

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Posted 13 August 2014 - 06:38 AM

View Postqxcontinuum, on 13 August 2014 - 05:30 AM, said:

Why exactly do we believe this is a comet and not an asteroid ? I am failing to see a comet as it should be an icy
body.Everything i see instead is a very ordinary celestial body that looks identical to a meteorite.
We dont believe, we know. The knowledge about 67P/C characteristic isn`t based on belief, its based on
facts generated by scientific knowledge and the use of modern scientific instruments like the Hubble telescope.
Comets produce a tail when close to the sun, asteroids dont.  And how can you jugde by just looking at a picture
of celestial body to determine of what material the body is made of?

Edited by toast, 13 August 2014 - 06:57 AM.

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#54    taniwha

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Posted 13 August 2014 - 07:05 AM

View Postqxcontinuum, on 13 August 2014 - 05:30 AM, said:

Why exactly do we believe this is a comet and not an asteroid ? I am failing to see a comet as it should be an icy body.
Everything i see instead is a very ordinary celestial body that looks identical to a meteorite.

It sure is a wonder.

Landing a human on it would be a great accomplishment!

Edited by taniwha, 13 August 2014 - 07:07 AM.

" Where does yesterday go to? Where does tomorrow come from? Is not the universe the proginetor of space and time? "
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                                                            http://www.unexplain...howtopic=286269

#55    Waspie_Dwarf

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Posted 13 August 2014 - 09:07 AM

View Postqxcontinuum, on 13 August 2014 - 05:30 AM, said:

I am failing to see a comet as it should be an icy body.
Take a look at this image and then say it's not a comet: HERE.

Comets frequently have an organic surface, the ice lies beneath. Rosetta has already detected water in the coma of 67P showing that it IS an icy body.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#56    Waspie_Dwarf

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Posted 13 August 2014 - 11:03 PM

Another newly released image:


Edited by Waspie_Dwarf, 13 August 2014 - 11:04 PM.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#57    Merc14

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Posted 14 August 2014 - 01:54 AM

View PostWaspie_Dwarf, on 13 August 2014 - 11:03 PM, said:

Another newly released image:

Great stuff.   Got to be some friction about where to land Philae given the terrain.

Edited by Merc14, 14 August 2014 - 01:56 AM.

Believing when there is no compelling evidence is a mistake.  The idea is to withhold belief until there is compelling evidence and if the universe does not comply with our predispositions, okay, then we have the wrenching obligation to accommodate to the way the universe really is.  - Carl Sagan

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#58    toyomotor

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Posted 14 August 2014 - 05:43 AM

And we need to know all of this-WHY?

Everything is possible,
Except the impossible.
And we're working on that.

#59    toast

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Posted 14 August 2014 - 07:38 AM

View Posttoyomotor, on 14 August 2014 - 05:43 AM, said:

And we need to know all of this-WHY?
Because we want it to know. Its called science.

“For every moment of triumph, for every instance of beauty, many souls must be trampled.”  - Hunter S. Thompson -
"Very funny, Scotty, now beam down my trousers!" - James T. Kirk -
"I think enormous harm is done by religion – not just in the name of religion, but actually by religion." - Steven Weinberg -  
"I am discounting the reports of UFOs. Why would they appear only to cranks and weirdos?" - Stephen Hawking -

#60    toyomotor

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Posted 14 August 2014 - 09:10 AM

View Posttoast, on 14 August 2014 - 07:38 AM, said:

Because we want it to know. Its called science.

Wanting and needing are two entirely different concepts.

Everything is possible,
Except the impossible.
And we're working on that.





Also tagged with comets, churyumov–gerasimenko, rosetta, philae, esa

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