Paper on Comet/Asteroid Impact Causing the Younger Dryas Cooling.

[Minimalist]

http://www.scribd.com/fullscreen/1423991...8cpxhhn8wm

We present detailed geochemical and morphological analyses of nearly 700 spherules from 18 sites in support of a major cosmic impact at the onset of the Younger Dryas episode (12.8ka). The impact distributed 10 million tonnes of meltedspherules over 50 million square kilometers on four continents. Origins of the spherules by volcanism, anthropogenesis,authigenesis, lightning, and meteoritic ablation are rejected ongeochemical and morphological grounds. The spherules closelyresemble known impact materials derived from surficial sediments melted at temperatures 2,200 °C. The spherules corre-late with abundances of associated melt-glass, nanodiamonds,carbon spherules, aciniform carbon, charcoal, and iridium.

Far too complicated for the theists..... stick with your silly fairy tales and leave the hard stuff to the scientists. Oddly, 12,800 years ago is more than double your precious 6,000 for the start of the whole fucking universe!

[Sal]

Looks like something Kent Hovind would believe. He had a similar hypothesis about mammoths being frozen by an "ice-asteroid" or something ridiculous or other.

[KichigaiNeko]

Min! You tease!

Frustrated geologist here who was about to go to bed

[The Grand Nudger]

Plenty of myths and legends about a catastrophic impact event coincide with the timeframe of the proposed younger dryas event. I'm actually a bit of a fanboi with this one. The snake in the sky left teardrop lakes all across north america..lol, for example. But maybe I just want to redeem these fairy tales we tell ourselves.

[KichigaiNeko]

Baby is heading to Central Australia in June and China in August for some of this fun.

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I think the aborigines here have a dreamtime story regarding this too Rhythm

[The Grand Nudger]

Minor aside..I fucking love dreamtime stories...lol.

[KichigaiNeko]

I don't know any thoroughly only bits and pieces.

Should look them up.

[Anomalocaris]

http://www.scribd.com/fullscreen/1423991...8cpxhhn8wm

We present detailed geochemical and morphological analyses of nearly 700 spherules from 18 sites in support of a major cosmic impact at the onset of the Younger Dryas episode (12.8ka). The impact distributed 10 million tonnes of meltedspherules over 50 million square kilometers on four continents. Origins of the spherules by volcanism, anthropogenesis,authigenesis, lightning, and meteoritic ablation are rejected ongeochemical and morphological grounds. The spherules closelyresemble known impact materials derived from surficial sediments melted at temperatures 2,200 °C. The spherules corre-late with abundances of associated melt-glass, nanodiamonds,carbon spherules, aciniform carbon, charcoal, and iridium.

The area covered by the supposedly impact derived spherules would be called a "strewn field".

Normally strewn field is associated with physical impact with the ground. ie where is the crater?

It is possible to imagine an object disintegrating in the atmosphere and making a strewn field of its own smithereens without ever actually hitting the ground in big blocks to make craters.

The problem is simulation seem to show the size of the strewn field described is not consistent with an object small enough to disintegrate during passage through the atmosphere. The atmosphere would have to be dozens of times denser than it actually is to cause any bolide large enough to make such a strew field disintegrate before hitting the ground. In earth atmosphere, such an object would be expected to survive intact until it hits the ground to make a crater several miles across.

So where is the crater?

It is of course possible a crater was actually made but remains undiscovered. However, the pattern of the strewn field from so recent an impact should be well preserved and should allow one to pin point where the undiscovered crater should be found.

So the theory provides a falsifiable prediction. Let's see who is going to try to test it.

[The Grand Nudger]

There are hypothesis about undiscovered and discovered craters (the most strained idea is that the exact crater is a subduction of the canary islands....) - but the idea that the atmosphere -simply must have had- a specific density ignores the density of any given airbursting object. It's not so much an issue of one particular object having a particular density as a issue of one -or the other- object having a particular density. If there was an airburst, it would have more to do with the density of the comet/object, and unfortunately- beyond spherules- we'd be at a loss to demonstrate it.

[Anomalocaris]

There are hypothesis about undiscovered and discovered craters (the most strained idea is that the exact crater is a subduction of the canary islands....) - but the idea that the atmosphere -simply must have had- a specific density ignores the density of any given airbursting object. It's not so much an issue of one particular object having a particular density as a issue of one -or the other- object having a particular density. If there was an airburst, it would have more to do with the density of the comet/object, and unfortunately- beyond spherules- we'd be at a loss to demonstrate it.

There is no plausible boilide that would have bulk density much less than water. So density of incoming object is pretty well bounded on the low end. On the lowest end would be a loosely consolidated carbon rich ice ball that has lost most of its other volatiles solids with desnity of around 50% that of water. Even with this low desnity and even it if it were 50 percent carbon, to have enough carbon to make 50 million tons of spherules it would still be almost 400-500 meters across. The reason why I say "it" has enough carbon is because we don't have a crater to suggest it hit and could have made a strewn field out of the ground it struck.

Once any object of a plausible composition and density, whatever its level of consolidation, reaches a certain size (usually around 200-300 meters across), it will survive substantially intact until ground impact (ie, at worst it will impact in a few large pieces representing majority of its original mass, and not a cloud of sand) in most plausible entry geometry because its mass and momentum now would dominate over its structural integrity in its reaction to reentry stress for the duration of atmosphere passage.

Hence the problem. If what is observed is indeed an impact strewn field, the impactor is expected to be too large not to leave a crater.

I concede there could be a crater that we haven't found. But that would seem less likely given how fresh and how large such a crater must be.

Other strewn fields without identified craters are all many scores of times older. The youngest I know of is well over half a million years old.