[meteorite-list] Extraterrestrial Impact Recreated in the Laboratory

[CMcdon0923 at aol.com]

??????

I've seen video of this type of test being performeded numerous times on various TV programs on places like The Discovery Channel, etc.

So unless I missed something here, what was so special about this test?


Craig





In a message dated 6/29/2004 12:50:03 PM Eastern Daylight Time, Ron Baalke <baalke at zagami.jpl.nasa.gov> writes:

>
>
>http://physicsweb.org/article/news/8/6/12
>
>Extraterrestrial impact created in the lab
>Belle Dume
>Physics Web
>22 June 2004
>
>Scientists in the Netherlands have successfully recreated a 
>small-scale meteoritic impact in the laboratory for the first 
>time. The novel yet simple experiment, devised by Detlef Lohse 
>and colleagues at the University of Twente, involves dropping a 
>small steel ball onto the surface of a sand bed. The results 
>could shed more light on the processes occurring during 
>large-scale impacts on Earth and other planets in the solar 
>system.
>
>Lohse and colleagues first prepared a sand bed, around 25 cm 
>thick, from fine sand grains measuring on average 50 microns 
>across. The sand was "decompactified" by blowing air through it 
>and then allowed to settle in an extremely loose-packed structure, 
>so that it essentially behaved like a fluid. Next, the scientists 
>dropped a steel ball, with a diameter of 2.5 cm, onto the sand 
>from various heights and angles while taking images with a 
>high-speed digital camera.
>
>The Twente team observed a series of well-defined steps: on impact, 
>sand is blown away in all directions to form a crown-shaped splash. 
>The ball then penetrates the sand and creates a void, which then 
>collapses under the influence of the hydrostatic-like pressure of 
>the sand. This pressure subsequently ejects sand grains into the 
>air to form jets (see figure). Using numerical simulations the 
>scientists developed a theory to explain how the void collapsed.
>
>"We have shown that the impact of an object on loosely packed 
>granular material can be well described by a simple, fluid 
>dynamical continuum model. So in our system sand behaves like 
>water!" team member Devaraj van der Meer told PhysicsWeb. "This 
>is very surprising since it has often been argued that, in general, 
>no continuum description of granular materials is possible," he 
>added.
>
>"There is a striking similarity with the large-scale impact of 
>meteors and other celestial objects on the surface of the Earth -- 
>for example the Chixulub impact crater in Yucatan, Mexico, thought 
>to be responsible for the extinction of the dinosaurs -- and our 
>experiment," said van der Meer. "Our scaled-down granular 
>experiments under laboratory conditions possibly capture the 
>essential features of these crucial events in the history of our 
>planet."
>
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