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 Post subject: More meteor crater info
PostPosted: Fri Feb 17, 2012 3:47 am 
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Shorah all,

From what I've been able to learn online, it's believed that meteors typically vaporize upon impact (it's very unusual to find much debris from the meteor itself). Here are a couple of sites that have some fairly easy to understand information about meteor impacts: University of Oregon, Smithsonian Institution (note that the Smithsonian also has an interactive version which has a lot of other geological information).

In looking for more images of craters, I was able to find a few that show some similarities to the Payiferen crater.

[spoiler=Barringer Crater in Arizona, a more typical crater with a single ring]Image[/spoiler]
[spoiler=The best example of a double ring formation is one on Mars]Image[/spoiler]
[spoiler=Here is another nice example in Australia; the outer ring is fainter but viewable when you pay attention to the shadowing]Image[/spoiler]
[spoiler=Another Australian crater; it is easier to see the dramatic difference between the inner and outer rings]Image[/spoiler]
In the last example above, the inner ring is partially obscured by the plant life and has largely worn down; but you can see a clear difference in the soil color and in the apparent fertility level, a good indicator that there is an important difference between the inner circle and the stretch of land between it and the obvious outer ring. This example bears one of the strongest resemblances to the Payiferen phenomenon simply because the outer ring is so dramatically high in comparison (though still nothing approaching the scale of the Payiferen mountains).

So I'm guessing that the ring features are typical of a meteor impact, though the double ring isn't necessarily common here on Earth. From the crater formation sites above, it looks like the ring(s) are formed by a combination of the meteor impact digging a hole in the earth and the ejecta from the explosive impact piling up. The formation of glass and other unusual minerals is also a typical result, though at least here on Earth, there is no apparent record of glass formation on the scale of the Payiferen mountains.

I still like the idea of the impact waves helping to create the Payiferen mountains, though am not sure how much hard scientific evidence there is to support it. So far, I haven't found anything discussing the phenomenon of double rings and how the outer ring is formed.

So more food for thought!

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PostPosted: Fri Feb 17, 2012 4:15 am 
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Well it occurs to me that the amount/thickness of atmosphere the meteorite passes through would also affect both the size and depth of the crater. Mars' is prettty thin, while Earth's is pretty "expansive." Less of the meteor would "burn off" during entry, due to reduced effect of friction upon it...or so goes my thinking on the matter. This would lead to a larger impact crater, and could perhaps make the "double ring" effect more prevelent. Not sure how much science would support this though. Any signs of similar effects of meteor impacts on Luna*?

(*Nevyn's Note: Just to be clear, I do not mean Luna, as in the GoMe GM/Messenger...but Luna, Earth's moon.)

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PostPosted: Fri Feb 17, 2012 5:11 am 
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There are plenty of impact craters on the Earth, Mars, and the Moon. The difference is that most of the big ones were created early in the Solar System's history, when there were more large asteroids and such junk floating around.

On Earth, these are almost all eroded away, since we have such an active atmosphere and weather. (Interesting exception I learned about recently: the Haughton impact crater in Canada. The weather is so consistently cold that it hasn't eroded much in the past 40 million years. Google Maps link: http://g.co/maps/268yy )

In more recent history, we get smaller meteors, and -- as you say -- they tend to burn up in Earth's atmosphere. (If this weren't true, we probably wouldn't be here!) On the Moon, practically any feature will last practically forever.

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PostPosted: Fri Feb 17, 2012 6:10 am 
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I found this during my independant research, thought I'd post it. It shows explains "complex" craters with a visual perfectly:

http://www.lpi.usra.edu/expmoon/science ... cture.html

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PostPosted: Fri Feb 17, 2012 8:56 am 
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Shorah all,

Nev'yn, thanks for that link. When I scrolled down the page, I saw that they show several of the craters on the Moon/Luna and at least one of them shows a distinct double ring. The article notes that it is one of the youngest Lunar craters, which implies that the inner/shorter ring probably tends to disintegrate more rapidly over time. And it appears that such double ringed features are called basins rather than craters (at least in regards to Luna).

[spoiler=Schrodinger Crater/Basin on Luna]Image[/spoiler]
[spoiler=On the left, another Lunar double ring crater/basin named Antoniadi]Image[/spoiler]
There is a 50-year-old and apparently seminal paper on Lunar basins which has numerous photos, many of them hand-enhanced, discussing the characteristics of basins (multi-ringed craters). I haven't read through the text itself but have scanned through the photos at the end and find it quite notable that there are a good many triple-ringed basins they show, all enormous and clearly quite ancient as they have been greatly eroded. I can only assume that they were formed originally back in the times belford describes, early in the lifecycle of our little solar system when there was a great deal more space debris floating around and smashing into things.

Particularly because of the enormous size of the Lunar basins discussed in the paper, the implication seems to be that meteor size and strength of impact creates multiple rings. The biggest basins of all in the illustrations are the triple rings, next biggest are double rings. (Of course, actually *reading* the paper may prove my thoughts off the mark :wink:.)

This is all in keeping with what we seem to be seeing in Payiferen, that the inner ring appears to be disintegrating and the outer ring is appearing to be more stable. In terms of what we see on our Moon/Luna, Payiferen seems to be notable in having such a distinct double ring when the overall basin size is relatively small. Thus, I am theorizing that the impact was probably from a relatively small meteor but that it hit extraordinarily hard.

[[stirring, stirring, stirring the pot :D ]]

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PostPosted: Fri Feb 17, 2012 12:34 pm 
If someone walked up to me and said that I would start a discussion about some wierd properties of rocks on a different planet, but it would up talking about meteorite impacts, I would have laughed. Yet, here we are, dicussing it! Oh well, never mind.
I think this idea is very interesting, and well worth investigating.

The crater doesn't necessarily need to be eroding away, since it is in a dry desert. The Nazca lines, after all, have survived when they would otherwise have disappeared long, long ago, since they are much shallower structures than an impact crater/basin. Thus, the rings could be very old, perhaps even dating back to the formation of the planet, when such impacts would be quite frequent. And perhaps those mountains are closer than they appear to be, so they could in fact be quite small in comparison. The certainly seem that way in the photos Ainia provided.


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 Post subject: Erosion thoughts
PostPosted: Fri Feb 17, 2012 6:56 pm 
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Shorah all,

True enough regarding rain/water erosion but don't forget that we have wind erosion at work. Although we don't know much about how long it's been windy here, I would think it can be measured in terms of centuries rather than decades or years. So I think it's a valid assumption that some sort of erosion figures into the big picture at Payiferen.

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PostPosted: Sat Feb 18, 2012 12:37 am 
True, but if the mountains are close enough, the inner ring may be sheltered enough to minimise erosion to a near-zero level.


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 Post subject: Payiferen winds
PostPosted: Sat Feb 18, 2012 9:00 am 
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Shorah all,

Unfortunately, I can personally attest that the Payiferen winds at the pod can be pretty wicked (although in all fairness, it is a great deal worse at Minkata). The Payiferen winds do not obscure the view (thankfully), but they do blow sand and dust constantly, which appear as the clouds of black particles in the vista photos I took earlier. I also suspect that this is why the Sandscrit has evolved the tough layer of hide we see on the top of his head and top of his back, and why he buries himself in the sand when he is not out foraging (his thickened head and back are the only exposed parts when he is buried).

[spoiler=Crater dust clouds look like black puffs from a distance]Image[/spoiler]
[spoiler=The top of the Sandscrit head and back is thickened]Image[/spoiler]
[spoiler=When not out foraging, the Sandscrit buries himself in the sand]Image[/spoiler]
So anyway, the only way to truly answer this question would be to do some longer-term studies; but in the meanwhile, I'm pretty sure we have some very suggestive evidence that there is erosion of some stripe at work here. Depending upon how tough the rock face is, this erosion might be quite mild and slow or quite pronounced and rapid (in geological terms). I think this would make an excellent research project for the future! I suspect that the D'ni may have been making a similar study back when they installed the pod here. (And it would be awesome if we someday discovered their research somewhere.)

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PostPosted: Sat Feb 18, 2012 11:35 am 
I think by 'long term study' you actually mean 'set up some monitoring equipment, hop in a time machine, go forward a thousand years, get the results, go back the the present, and analyse the data'. Am I close?


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PostPosted: Sat Feb 18, 2012 4:05 pm 
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I'll check with Professor Almaron to see if the DMoA records have uncovered anything in their researches into the D'ni. You know how damaged some of the records within the Archives are, however....

P.S. No time trips! Kadish and that weird Age of Ahnonay is quite enough, thank you!!!

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PostPosted: Sat Feb 18, 2012 5:31 pm 
*Grins*


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 Post subject: Time travel
PostPosted: Sat Feb 18, 2012 7:38 pm 
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Shorah all,

Actually, I had in mind something a bit more modest in terms of a study. Something along the lines of taking erosion measurements over the course of several years and then extrapolating in both directions (forward and backward). But time travel sounds a lot more fun! When do we leave?? I can be packed up and ready to go almost immediately! :D

(And I assume we have a friendly Bahro on board to help with the time travel bit! :wink: )

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PostPosted: Sat Feb 18, 2012 10:17 pm 
I've already briefed Yeesha, and she's all set!


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PostPosted: Wed Feb 22, 2012 7:28 am 
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Here's my two cents.

First a little background. I have a master's degree in geology and wrote my thesis on martian volcanoes. You can use counts of the numbers of impact craters on a lava flow to estimate it's age.

Ainia noticed there was a relationship between the size of the impact crater and the number of rings it has. In fact you can estimate the size of a crater this way. On the moon, impact craters less than 20 km in diameter are simple bowl-shapes. Craters between 20 and 200 km have a peak in the center of the depression. You only start to see multiple rings in craters larger than 300 km. Earth has higher gravity than the moon, so you start to see central peaks at smaller diameters -- somewhere around 7-15 km -- and the smallest rings should be maybe 5 km in diameter (that's a guess).
*End of planetary geology lecture*

My exhaustive geologic studies of Payiferen (eg. my avvie jumps to the same height on Payiferen as she does on Earth :D ) suggest that it is a planet with gravity approximately the same as Earth's, so I believe you will start to see complex crater structures at sizes similar to Earth craters.

The crater on Payiferen appears to be less than 1 km in diameter. It is far too small for multiple ring structures. I also have trouble accounting for such large boulders in the center of such a small crater. They are something of an anomaly.

So I have two theories:

Theory One: The Payiferen structure is actually two impact events superimposed on each other, the smaller crater is coincidentally lined up with a slightly larger, older crater. The rings you see are actually the crater rims of the two separate craters.

Theory Two: This crater is quite old. It impacted into layered sedimentary rocks in which two hard, resistant layers are separated by soft layers that are easily eroded. The impact caused the rocks to warp upwards and millions of years of erosion has left the hard layers exposed as ridges and the soft layers as the low areas between the ridges. Upheaval Dome in Utah would be an example of this. This theory may also account for the large boulders in center of the crater. They could be erosional remnants of the hard rock layers.

Are you bored yet?

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