Comments on: The Purloined Crater http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/ I am an astronomer, writer, and skeptic. I likes reality the way it is, and I aims to keep it that way. My real name is Phil Plait, and I run the Bad Astronomy blog. Tue, 24 Nov 2009 23:01:12 -0600 http://wordpress.org/?v=2.8.4 hourly 1 By: Andras Zboray http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/comment-page-1/#comment-12727 Andras Zboray Mon, 10 Jul 2006 18:10:17 +0000 http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/#comment-12727 "Kebira", just like Paillou's "crater field", appears to be the product of trying very hard to find exactly what one is looking for. We recently visited the "Kebira" area, and found the "central uplift" to be an eroded outlier of the surrounding sandstone plateau, with undisturbed horizontal bedding throughout. The feature is the result of erosion, no evidence of impact origin. The same is true for Paillou's crater field, which have been visited both by myself and several other geologist groups. All the features described are clearly non-impact origin. “Kebira”, just like Paillou’s “crater field”, appears to be the product of trying very hard to find exactly what one is looking for.

We recently visited the “Kebira” area, and found the “central uplift” to be an eroded outlier of the surrounding sandstone plateau, with undisturbed horizontal bedding throughout. The feature is the result of erosion, no evidence of impact origin.

The same is true for Paillou’s crater field, which have been visited both by myself and several other geologist groups. All the features described are clearly non-impact origin.

]]> By: mr.x http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/comment-page-1/#comment-12713 mr.x Sat, 25 Mar 2006 17:45:16 +0000 http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/#comment-12713 Can I ask how you figure on 200,000 megatons equivalent for the impact strength. I would be interested in the inputs of the equation. If one hit Earth today, likely it would land in the Ocean. Are we able to detect crater marks on the surface of the Ocean? Whats the biggest crater impact we know of in the solar-system? Can I ask how you figure on 200,000 megatons equivalent for the impact strength. I would be interested in the inputs of the equation.

If one hit Earth today, likely it would land in the Ocean. Are we able to detect crater marks on the surface of the Ocean? Whats the biggest crater impact we know of in the solar-system?

]]> By: James McEnanly http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/comment-page-1/#comment-12726 James McEnanly Thu, 16 Mar 2006 02:38:38 +0000 http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/#comment-12726 Those arced hills at 2 and four o'clock, as will as the long one between 10 and noon would be a good indication of a crater. I an wondering if he had access to a topographic map of the area. I hae read somewhere that when Galileo first saw large craters on the Moon, he described it as being a walled plain, like Bohemia. Has anyone checked that area to see if there are any signs of an impact? Those arced hills at 2 and four o’clock, as will as the long one between 10 and noon would be a good indication of a crater. I an wondering if he had access to a topographic map of the area.
I hae read somewhere that when Galileo first saw large craters on the Moon, he described it as being a walled plain, like Bohemia. Has anyone checked that area to see if there are any signs of an impact?

]]> By: Charles O'Dale http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/comment-page-1/#comment-12725 Charles O'Dale Thu, 16 Mar 2006 00:03:57 +0000 http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/#comment-12725 To add to the Kebira structure discussion, the Paper: “Discovery of the largest impact crater field on Earth in the Gilf Kebir region, Egypt”, Philippe Paillou (et al), documents the presence of shattercones and planar deformation features in the structures documented in the paper. These are positive indicators of an impact event. This crater field is less than 300 km to the east of the Kebira structure. A field trip to the Kebira structure will be required to finally determine if it is an impact crater (or not). To add further to this "crater search" discussion, for some time now I have thought that "maybe" the Manicouagan structure is a "double" impact site comparable to the Clear Water Lake double craters, both in northern Quebec, Canada. Looking at the Manicouagan structure at N 51° 23' W 68° 42', notice that there is a "second" circular structure immediately to the north. I have illustrated this at: http://www.ottawa.rasc.ca/astronomy/earth_craters/possible_craters/index.html (look half way down the page) I highlighted the "circular" structure on the aeronautical chart. The geology in the area shown on the aeronautical chart reveals that: a.. The contour lines denoting an increase in elevation of the Precambrianrocks to the north of the structure follows a semicircle; b.. Two rivers on the east and west of the feature form an enclosingsemi-circle around the structure; and c.. There is a central peak. This could simply be the result of my "fertile" immagination, or could it? Charles O'Dale Meeting Chair Ottawa RASC http://www.ottawa.rasc.ca/astronomy/earth_craters/index.html To add to the Kebira structure discussion, the Paper:
“Discovery of the largest impact crater field on Earth in the Gilf Kebir region, Egypt”, Philippe Paillou (et al), documents the presence of shattercones and planar deformation features in the structures documented in the paper. These are positive indicators of an impact event. This crater field is less than 300 km to the east of the Kebira structure. A field trip to the Kebira structure will be required to finally determine if it is an impact crater (or not).

To add further to this “crater search” discussion, for some time now I have thought that “maybe” the Manicouagan structure is a “double” impact site comparable to the Clear Water Lake double craters, both in northern Quebec, Canada.

Looking at the Manicouagan structure at N 51° 23′ W 68° 42′, notice that
there is a “second” circular structure immediately to the north. I have
illustrated this at: http://www.ottawa.rasc.ca/astronomy/earth_craters/possible_craters/index.html (look half way down the page) I highlighted the “circular” structure on the aeronautical chart. The geology in the area shown on the aeronautical chart reveals that:
a.. The contour lines denoting an increase in elevation of the Precambrianrocks to the north of the structure follows a semicircle;
b.. Two rivers on the east and west of the feature form an enclosingsemi-circle around the structure; and
c.. There is a central peak.

This could simply be the result of my “fertile” immagination, or could it?
Charles O’Dale
Meeting Chair
Ottawa RASC http://www.ottawa.rasc.ca/astronomy/earth_craters/index.html

]]> By: Charles O'Dale http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/comment-page-1/#comment-12724 Charles O'Dale Wed, 15 Mar 2006 23:54:19 +0000 http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/#comment-12724 To add to the Kebira structure discussion, the Paper: "Discovery of the largest impact crater field on Earth in the Gilf Kebir region, Egypt", Philippe Paillou (et al), documents the presence of shattercones and planar deformation features in the structures documented in the paper. These are positive indicators of an impact event. This crater field is To add to the Kebira structure discussion, the Paper:
“Discovery of the largest impact crater field on Earth in the Gilf Kebir region, Egypt”, Philippe Paillou (et al), documents the presence of shattercones and planar deformation features in the structures documented in the paper. These are positive indicators of an impact event. This crater field is

]]> By: Allen http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/comment-page-1/#comment-12723 Allen Wed, 15 Mar 2006 22:09:44 +0000 http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/#comment-12723 Where is the picture? Where is the picture?

]]> By: Daniel Fischer http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/comment-page-1/#comment-12722 Daniel Fischer Wed, 15 Mar 2006 21:42:07 +0000 http://blogs.discovermagazine.com/badastronomy/2006/03/14/the-purloined-crater/#comment-12722 Where is the proof that this structure is an impact crater? According to the BU Press Release there are only satellite images yet no field studies so far. Gene Shoemaker himself taught me (i.e. told me during a lunch break at Fred Whipple's 90th birthday party, to be exact) that you must not trust any impact crater until you've been digging around in it yourself - there are just too many other round structures in terrestrial geology. So publishing this discovery as an impact crater, let alone the source of the desert glass, instead of calling it a "crater candidate", was Bad Astronomy indeed! Where is the proof that this structure is an impact crater? According to the BU Press
Release there are only satellite images yet no field studies so far. Gene Shoemaker
himself taught me (i.e. told me during a lunch break at Fred Whipple’s 90th birthday
party, to be exact) that you must not trust any impact crater until you’ve been digging
around in it yourself – there are just too many other round structures in terrestrial
geology. So publishing this discovery as an impact crater, let alone the source of the
desert glass, instead of calling it a “crater candidate”, was Bad Astronomy indeed!

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