Prehistoric meteor shower? Options

[tty]

A real weird news story from Nature about meteor damage to pleistocene fossils:

http://www.nature.com/news/2007/071212/ful...s.2007.372.html

If traces of this meteor shower has been found in both Siberia and Alaska as the story implies, then multiple impactors must have been involved. Such small meterites would lose speed quickly so the airburst must have occurred at fairly low altitude.

[djellison]

But surely a meteorite fragment that small would cool in the 'flight' phase?

Doug

[nprev]

But surely a meteorite fragment that small would cool in the 'flight' phase?

Doug

Not sure; lots of variables. Metal doesn't cool very rapidly in air anyhow, and if the frags aren't really traveling that fast then they'll cool even less. Grenade fragments are hot as hell for several minutes after detonation, for example...

Tasp, it also appears that these things (whatever they are) didn't necessarily kill all the animals that they hit. Some of the bones showed signs of long-term healing.

[helvick]

... Metal doesn't cool very rapidly in air anyhow, and if the frags aren't really traveling that fast then they'll cool even less. Grenade fragments are hot as hell for several minutes after detonation, for example...

Yes but grenade fragments travel a few tens of meters at most - if they were to travel through hundreds or thousands of meters of air they would cool rapidly.

I'd like to see someone work out a viable model that creates thousands\millions of small high velocity (or high temperature) fragments at ground level from a meteor entering the atmosphere _without_ noticable blast effects. I'm going to see what I can get from just running velocity\drag\density and range numbers.

[hendric]

Yes but grenade fragments travel a few tens of meters at most - if they were to travel through hundreds or thousands of meters of air they would cool rapidly.

Doesn't that depend on their speed though? Above a certain speed, they are going to get hotter, and below that speed, they are going to cool off. I could easily see that switchover at 1-2km/sec. Granted, it might be quickly decelerating, but a metal fragment is pretty darn dense. Bullets can travel for miles, so I can see a small, mostly metallic fragment, starting off hot at 3-4 km/sec, travelling for quite some distance, potentially tens of miles, and still be hot enough to burn bone upon impact.

Dr. Burt, where are you on this? These fragments are proof, so to speak, of an impact surge! How does their size compare to the blueberries and other impact surge fragments?

With that said, it's interesting there are actually different sizes of fragments in the same tusk. I'm sure a reasonable model could be made of how far away the impact would have to be to allow fragments of the minimum size to penetrate the tusks. At the least, the model should give a minimum distance.