[meteorite-list] Impact Crater Dynamics in the Laboratory

[MexicoDoug at aol.com]

06/29/2004 10:05:27 PM Mexico Daylight Time Professor Detlef Lohse escribe:

>>Thanks for your nice words. You carefully read the paper.  
>>We made the sand flushy to destroy the force chains.  
>>In this way hardly any energy is stored in the ground, 
>>and the energy of the object is overwhelming. The 
>>geophysics community calls this gravity driven. I just 
>>talked about this at the Gordon conferences here in Colby,
>>Maine, USA and the geophysicists who were around 
>>viewed it favorably.

>>Best regards, Detlef Lohse

Dear Meteorite-list,

I am forwarding the above friendly response from Dr. Lohse, the physicist 
from the Netherlands who designed the recent impact experiment and whose area of 
study is events of singularity.  Apparently has just discussed the recent work 
modeling terrestrial impacts under discussion here at the physics' symposia 
"Gordon Conference" currently held in the US.

In his reply he emphasizes that the ratio of the impactor's energy to that of 
the potential energy in the ground makes the latter negligible.  That's the 
case expected for the real asteroid impacting events.  That suggests to me that 
it is the first time someone has actually modeled such an energy differential 
in the laboratory, helping to earn the work the honor of "first scalable 
impact event created in the laboratory", not to mention the differences they 
identified vs. videos relating to unique sedimentation and reverse jet they worked 
the physics out on which are different from liquid models that have been 
already investigated.  

For example, it supports the idea that the meteorite winter that helped wipe 
out the dinosaurs was caused by terrestrial ejecta jetted in reverse along the 
entry trajectory, rather than from a splash, as most videos would indicate.  
That was done by an interesting, basically two dimensional cross experiment 
that I have never seen in a video.  But then again you folks in the US are more 
privileged than much of the rest of the world when it comes to the media.  The 
work also might also be useful to investigate under what impact conditions an 
earth meteoroid might theoretically be produced, which has previously been a 
topic of much interest to this group.

The goal of this work was clearly not to film any collision which will 
obviously help one get a handle on collisions in general, such as a drop falling on 
apuddle, and what happens on a small time scale; it was to reporduce for the 
first time the energy ratios contemplated for Earth's big extinction events. I 
hope the 599 other members of the meteorite list will join with me in wishing 
him congratulations and further encouragement to refine the results on 
sedimentation patterns and the resulting stress patterns in this interesting impact 
research, and thanks to Ron Baalke at JPL for the initial post alerting us to 
this.  The list is described at http://www.meteoritecentral.com and has members 
who are interested in all aspects of meteorites, impacts, for the scientific, 
hobby and resulting commerce of meteorite trade.

Saludos,
Doug Dawn
N. 25.4° W. 100.2°
Mexico
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