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Arrowheads, Tomahawks And Big Guns

Originally published March 12, 2011 LPOD-Mar12-11.jpg
images from talk at LPSC 42 by Peter Schultz and A.M. Stickle, Brown University

Not quite the Columbiad of Jules Verne, but close. Rather than shooting for the Moon, Peter Schultz shoots to make the Moon, or at least to model the craters and basins. In a talk that Chuck and I attended at LPSC 42 this afternoon, Peter Schultz described how impacts that he and A.M. Stickle both of Brown University created using the Nasa Ames Vertical gun, the projectile gets sheared off, or "decapitated", and the decapitated part of the projectile travels downrange and causes a large secondary impact or modification of the downrange wall. Part of the projectile is sometimes left in the uprange wall of the primary crater also. By impacting at hypervelocity (5.2 km/sec) obliquely into a curved aluminium plate (A) or a flat plate (B) with a glass bead he found that on the curved surface the decapitated projectile travels downrange and forms a secondary impact, while on the flat plate, it modifies the downrange crater wall. The scours in B correspond to similar areas in Mare Crisium at areas C and D in the image on the right. The fan tail shape of Mare Crisium was likened to a Tomahawk shape (or a fish as one commenter said!). It also provided an alternative explanation to our idea of the double impact of Mare Moscoviense also. The crater Petavius-B is an example of an arrowhead crater formed by an oblique impact by this model. Today was the last day of this years Lunar and Planetary Science Conference.

Maurice Collins

P.S. Chuck is on his way home tonight, so he asked me to fill in for him for LPOD today. I wish Chuck safe travels home, and I thank him so much for everything he has done in making this visit an experience of a lifetime! It was so nice to finally meet him in person!

Technical Details
Arrowhead Craters and Tomahawk Basins: Signatures of Oblique Impacts at Large Scales
P. H. Schultz, A. M. Stickle
42nd Lunar and Planetary Science Conference (2011), Abstract #2611

Related Links
http://www.space.com/1222-gunning-crash-rehearsing-deep-impact-comet-collision.html
LPSC 42

Yesterday's LPOD: From LPOD To the Big Time

Tomorrow's LPOD: Six Views of Opportunities



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