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How much $$$ for a gram of Interplanetary Dust Particles?

Hello List,

The current issue of the journal SCIENCE (v. 280, n. 5367, 22 May 1998) has an interesting article by Farley, Montanari and the Shoemakers entitled, "Geochemical Evidence for a Comet Shower in the Late Eocene."

They conclude that the Popigai and Chesapeake Bay impact craters were formed about 36 million years ago by a comet shower that increasingly bombarded Earth over a sustained 2.5 million-year period.  Towards the end of the sustained showering, the two craters were formed by larger impacts.  They believe the comet shower was triggered by a perturbation of the Oort cloud.  They do not believe this was a periodic event triggered by galactic tidal forcing that could repeat itself (whew...I know you all were worrying and losing sleep about that!).

The research team studied 79 limestone samples of what were once pelagic (ocean) sediments during the Cenozoic era.  They found extraterrestrial matter in the form of 3He-enriched, fine-grained Interplanetary Dust Particles (IDPs).  3He only survive delivery to the Earth as very fine-grained IDPs since bodies larger than a few tens of micrometers in diameter are intensely heated and lose their 3He to space.  They used this evidence to produce an exhaustive analysis (described in the article) to ultimately determine that the IDPs originated with a comet and not from an asteroidal collision.

So those of you who have been looking for meteorite fragments from the Popigai and Chesapeake Bay impact craters can forget about finding any!  However, some very-fine Interplanetary Dust Particles can be found in the limestones.  Alright, all you dealers out there in List Land...how much is a gram of pure IDP actually worth?

Steve

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Steven Excell
Seattle, WA 98102 USA
E-Mail: excell@concentric.net
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