[meteorite-list] Extraterrestrial Impact Recreated in the Laboratory

From: CMcdon0923_at_aol.com <CMcdon0923_at_meteoritecentral.com>
Date: Tue Jun 29 15:01:17 2004
Message-ID: <34E638FA.1D76485C.0A2C07BE_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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Received on Tue 29 Jun 2004 03:01:12 PM PDT