[meteorite-list] debate in The Skeptical Inquirer re Younger Dryas Boundary comet fragment swarm: David Morrison: C. Leroy Ellenberger: Rich Murray 2010.08.28

[Rich Murray]

debate in The Skeptical Inquirer re Younger Dryas Boundary comet fragment 
swarm: David Morrison: C. Leroy Ellenberger: Rich Murray 2010.08.28
http://rmforall.blogspot.com/2010_08_01_archive.htm
Saturday, August 28, 2010
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http://cosmictusk.com    blog

[ Submitted Comment ]
[ Minor editing of typos and to increase ease of reading, by Rich Murray ]

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Thursday,  August 26, 2010

Dave,

As you probably know, the Sep/Oct Skeptical Inquirer (whose cover features 
Martin Gardner) contains letters by Clark Chapman and Paul Hilfinger, 
reacting to your May/Jun article on the claimed impact at the Younger Dryas 
boundary,
([also] with a letter from Mark Bosslough commenting on his sidebar about 
scientists changing their minds, citing the recent example of Wallace 
Broecker)
[along] with your response, which includes the following passage:
"Such huge swarms of super-Tunguska impacts [for the Carolina Bays and the 
YD impact] are inconsistent with what astronomers know about our planet's 
cosmic environment or geologists' understanding of Earth's recent impact 
history.
This is not just improbable; in common usage we would have to call it 
impossible."

Dave, I almost hate to say this, but in almost every particular here you are 
WRONG because:

1) the British astronomer Bill Napier has explained this year in MNRAS how 
Earth might well have encountered such huge swarms of super-Tunguska 
impactors from the debris of a recently disintegrated comet only 13,000 
years ago (despite Chapman seconding you on this point),

and 2) American geologist Adrian Melott et al. have this year presented 
evidence in GEOLOGY for a large impact at the YDB based on the ammonium 
signal in the Greenland ice.

The publication of the paper contradicts Chapman's statement in his letter, 
"Nor has the Greenland paper been published in  _any_  peer-reviewed 
scientific journal during the subsequent year."

Furthermore, there need not have been two events IF the admittedly 
controversial extra-terrestrial origin of the Carolina bays was part of the 
same impact event at the YDB, but this issue is beyond the scope of my 
concerns here.

Your failure  to take into account these two developments vitiates the 
thrust of your article.

Also, I find it of passing interest that Hilfinger's letter correcting you 
on a probability issue ("That is, Tunguska does not 'protect' us from 
immediate future impacts.") is the same issue on which my unpublished letter 
to Sky & Telescope in Sept. 2009 corrected Mark Boslough, i.e., the 
occurrence of a low probability event does not mean that a second, similar 
low probability event cannot happen very soon after the first.

The letter below was submitted to Skeptical Inquirer in early July, possibly 
too late to be included in the Sep/Oct issue, but in light of the tenor of 
Clark Chapman's letter ("I wish to expand on David Morrison's excellent 
special report . . . on the widely publicized claim that a huge broken-up 
comet collided with Earth just 13,000 years ago, wiping out mammoths, Clovis 
culture, and so on. . . ."), excoriating the AAAS for awarding top prize to 
the NOVA TV documentary on the Younger Dryas Impact shown on PBS.

Perhaps I was too optimistic about SI's interest in "fair and balanced" 
scientific reporting.


[ early July letter to SI by C. Leroy Ellenberger ]

Cosmic Impact at Younger Dryas Boundary

In response to David Morrison's attempt to quash the possibility that a 
cosmic impact killed the mammoths approximately 12,900 years ago (SI, 
May/June 2010), Mark Twain might have responded that the report that such an 
impact has been disproved is exaggerated.

Certainly Morrison correctly points out scientific problems in some 
descriptions of the event; but he fails to deal with recent developments 
that nevertheless support a cosmic impact at the Younger Dryas boundary.

Three issues merit comment here:

Morrison claims, "There was apparently no way to get a swarm of impactors to 
target North America alone," while assuming that a comet disintegrated just 
before encountering Earth; but this objection has been overcome by British 
astronomer Bill Napier who, in a recent publication, describes how robust 
meteorid streams (comet debris trails) would be the inevitable result of the 
disintegration within the past 20-30 KYr of the progenitor of the Taurid 
Complex in near-Earth space, and that, "encounters with dense swarms of 
material, sufficient to produce a 12.9 ka cosmic event, are indeed 
reasonable expectations of recent Earth history."

Morrison's criticism concerning impact frequencies does not envision the 
former existence of a large comet in a short period orbit whose 
disintegration gave rise to the Earth-orbit-crossing Taurid Complex which 
then contained myriads of large debris.

Concerning the presence of nanodiamonds, Morrison misstates D.J. Kennett et 
al.'s position in Science, who stated, "Nanodiamonds . . . are associated 
with known impacts, during which they may arrive inside the impactor or form 
through shock metamorphism. . . ."

Morrison improperly ignored the prospect of their arrival inside the 
impactor, which was the case with the Tagish Lake meteorite (arguably part 
of the Taurid Complex) that fell over British Columbia in January 2000, and 
contained the highest abundance of nanodiamonds yet seen.

Conversely, Morrison's remark, "Most impact experts agree that nanodiamonds 
were unlikely to have been formed in the impact," is contradicted by the 
discovery of nanodiamonds at the Cretaceous-Tertiary boundary, that most 
likely formed from terrestrial material during the impact.

Finally, airbursts from cometary fragments can be expected to produce 
copious amounts of ammonium ion, which are captured and preserved in 
glaciers, especially the Greenland ice cap.

A.L. Melott et al. in the April 2010 Geology analyzed the ammonium signals 
in the Greenland ice from the Tunguska airburst of June 30, 1908, which 
cannot be explained by wildfires from the explosion, and also at a depth in 
the ice corresponding to the onset of the Younger Dryas 12,900 years ago.

This is presumptive evidence for a cosmic impact at that time, regardless 
Morrison's attempts to discount such a possibility.

References

Napier, W. M. 2010.
Palaeolithic extinctions and the Taurid Complex.
Mon.Not. R. Astron. Soc. 405(3): 1901-1906.

Kennett, D. J. et al. 2009.
Nanodiamonds in the Younger Dryas Boundary
Layer. Science 323: 94.

Gilmour, I. et al. 1992.
Terrestrial carbon and nitrogen isotopic ratios
from Cretaceous-Tertiary boundary nanodiamonds.
Science 258: 1624-1626.

Melott, A. L. et al. 2010.
Cometary airbursts and atmospheric chemistry:
Tunguska and a candidate Younger Dryas event.
Geology 38: 355-358.

C. Leroy Ellenberger
St. Louis, Missouri

URLs to Napier and Melott:

Napier:
http://arxiv.org/PS_cache/arxiv/pdf/1003/1003.0744v1.pdf

Melott:
http://geology.geoscienceworld.org/cgi/reprint/38/4/355

All the best,
Leroy Ellenberger
http://en.wikipedia.org/wiki/C._Leroy_Ellenberger

August 27th, 2010,  Category: Uncategorized,  One comment


[ Rich Murray adds:

http://www.csicop.org/si/

http://www.csicop.org/si/archive/category/volume_34.3

Skeptical Inquirer - Volume 34.3  May / June 2010

http://www.csicop.org/si/show/when_scientists_actually_change_their_minds/

When Scientists Actually Change Their Minds
by Mark Boslough
Volume 34.3, May / June 2010
Broecker's esteem among scientists was not diminished when he changed his 
mind.
The Younger Dryas impact proponents would do well to follow his example.

http://www.csicop.org/si/show/did_a_cosmic_impact_kill_the_mammoths

Did a Cosmic Impact Kill the Mammoths?
by David Morrison
Volume 34.3, May / June 2010
The rise and fall of the theory that cosmic catastrophes altered human 
prehistory in North America.

David Morrison

Dr. David Morrison is the Senior Scientist at the NASA Astrobiology 
Institute.
His primary interests are the new multidisciplinary science of astrobiology, 
the protection of Earth from asteroid impacts, and science outreach and 
education.
Dr. David Morrison is the Director of the NASA Lunar Science Institute and 
Senior Scientist for Astrobiology at the NASA Ames Research Center. He is 
also the Director of the Carl Sagan Center for Study of Life in the Universe 
at the SETI Institute, in Mountain View CA.
Dr. Morrison is internationally known for his research on small bodies in 
the solar system, and has more than 155 technical papers and has published a 
dozen books, including five university-level textbooks and several popular 
trade books on space science topics.
In 2005 he received the Carl Sagan medal of the American Astronomical 
Society for communicating science to the public.
He is a Fellow of the American Association for the Advancement of Science, 
the California Academy of Sciences, and the Committee for Skeptical Inquiry.
Asteroid 2410 Morrison is named in his honor.

http://www.sandia.gov/news/resources/releases/2007/asteroid.html

See the Mark Boslough supercomputer 3D simulations of meteor air bursts
becoming complex directed flows of very high temperature and pressure plasma
plumes -- 2007 -- Dennis Cox gives evidence that this was real on a
continental scale, causing "vertical ablation".

http://craterhunter.wordpress.com/  ]