[meteorite-list] KT extinction impacts

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 27 Apr 2011 19:06:49 -0500
Message-ID: <3A352806965141CDAD5BB08CC8C2F7B4_at_ATARIENGINE2>

Very Nice Calculator, Keith

And useful for a wide variety of cases. A sophisticated
model behind it. But... we know E. P. -- I suspect he's
interested in Big Thumpers, mostly. And the bigger
(and faster) the impactor, the more energy-dominated
the event becomes. And since the topic was the K-T
Visitor, I assumed we were talkin' Big... Not "the size
of Texas," as the memorable Billy Bob Thornton line
has it, but Big...

I noted that I stole this from the very best sources,
namely John S. Lewis' "Physics and Chemistry of
the Solar System, Second Edition" (pp.438-445).
And simplified it slightly.

And when I plug suitably big and fast impactors
into your model, I get results essentially similar
to the thumb rules, but that's because I'm choosing
events in size Large, X-Large, and 2X-Large...

No, it's the Devilishly Small impactors, where a
variety of factors matter greatly, that are a mess
to calculate. Now, I will go back to my favorite
Impact Calculator Game: finding the inputs that
will land a 100-ton HOBA without making a crater...
or a pit.


Sterling K. Webb
----------------------------------------------------------------------
----- Original Message -----
From: "Keith Holsapple" <holsapple at aa.washington.edu>
To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
Cc: "E.P. Grondine" <epgrondine at yahoo.com>;
<meteorite-list at meteoritecentral.com>; "ACC Bill Allen"
<ballen at hohmanntransfer.com>; "Astronomer" <meb at star.arm.ac.uk>; "Ted
Bunch" <tbear1 at cableone.net>; <burchar at math.okstate.edu>; "phil burns"
<pib at pibburns.com>; <c.leroy.ellenberger at wharton.upenn.edu>;
<cavetank at aol.com>; <dallas at ldeo.columbia.edu>; <dja at star.arm.ac.uk>;
"Duncan" <duncansteel at grapevine.com.au>; "Leroy Ellenberger"
<c.leroy at rocketmail.com>; "Richard Firestone" <rbfirestone at lbl.gov>;
"Richard Firestone" <rbf at lbl.gov>; "George Howard"
<george at restorationsystems.com>; "Elton Jones" <mstreman53 at yahoo.com>;
"Kennett" <dkennett at uoregon.edu>; "Bob Kobres" <bkobres at uga.edu>; "Raoul
Lannoy" <raoul.lannoy at pandora.be>; "W. Bruce Masse" <wbmasse at lanl.gov>;
<napierwm at cardiff.ac.uk>; "bernd pauli" <bernd.pauli at paulinet.de>;
"Benny Peiser" <benny.peiser at thegwpf.org>; "Tree Rings"
<m.baillie at qub.ac.uk>; "Peter Schultz" <Peter_Schultz at brown.edu>;
<tankerkh at uc.edu>; "Oscar Alfredo Turone" <oaturone at sinectis.com.ar>;
"Allen West" <Allen7633 at aol.com>
Sent: Wednesday, April 27, 2011 1:58 PM
Subject: Re: [meteorite-list] KT extinction impacts


I think we can make much better estimates based on modern crater scaling
theories than the old (1960's) energy-based ones. And while the scaling
may be complex to a newbie, it is easily evaluated: I invite anyone to
make use of my web page at
http://keith.aa.washington.edu/craterdata/scaling/index.htm and push the
buttons to estimate the crater from any impact or explosive source.


On Apr 26, 2011, at 9:55 PM, Sterling K. Webb wrote:

> Dear E.P.
>
>> Sterling, do you have a public formula handy for
>> converting craters into megatons in a very rough
>> number? ...perhaps he will generate a very easy to use
>> oversimplified rough approximation formula for
>> Earth impacts.
>
> There ARE some simplified model equations for crater
> size and impact energy, hence impactor size, and
> there certainly are some quick and rough ones.
>
> [Note: I stole this from the very best sources...]
>
> Consider a 100-m chunk of asteroidal material
> encountering the surface of a rocky planet at a speed
> of 20 km/s. The kinetic energy density of the impactor
> is 1/2 (2 x 10^6)^2 or 2 x 10^12 erg/g. The energy
> required to crush a typical rock is a little above
> 10^8 erg/g. [A joule is 10^7 ergs]
>
> To heat it to its melting point requires about 10^10
> erg/g and to vaporize it requires less than 10^11
> erg/g. Thus the impactor carries enough kinetic
> energy to not only vaporize itself completely, but also
> crush up to roughly 1000 times its own mass of target
> rock, melt roughly 100 times its own mass, or vaporize
> about 10 times its own mass. Alternatively, it carries
> enough kinetic energy to accelerate 100 times its own
> mass to a speed of 0.1 times its impact speed.
>
> In reality, an impact does all of these things to some
> degree and divides its energy over all these possible
> outcomes. Thus an impactor may crush 1000 times
> its own mass of rock, melt 10 times its mass,
> vaporize a few times its own mass, and eject 100
> times its mass at speeds of tens to hundreds of
> meters per second and still give off a substantial
> amount of energy as seismic waves and radiation
> from the fireball.
>
> Crater sizes are of course generally related to the
> kinetic energy content of the impactor. For relatively
> SMALL impacts the critical factor in determining the
> target's resistance to the explosion is the strength of
> the material, S (dyn/cu.cm.). If S > density x g x crater
> diameter at the level of the target surface, then the
> crater excavation process is strength limited (the "g"
> equals the surface gravity of the planet; in the case
> of Earth, g = 1).
>
> In this case, the diameter scales as:
>
> D (km) roughly equals the cube root of W,
>
> where W is the explosion energy in units of millions of
> tons of TNT equivalent (megatons; Mt). For very large
> impacts, no material has enough strength to matter, and
> the cratering process depends only on the gravitational
> environment in which it occurs:
>
> D (km) roughly equals the fourth root of W/g
>
> For a rule of thumb for craters from a few kilometers up
> to 100 km or more with impactor speeds of 25-30 km/s,
> the crater is nine or ten times the size of the impactor,
>
> If you find a 100-km crater on Earth, you can figure
> the impactor was 8-9 km if fast and 11-12 km if slow,
> and delivered 100 (crater diameter) ^ 4, or 100,000,000
> megatons. Chicxulub, in other words.
>
> You can do that much with a thumb...
>
>
> Sterling K. Webb
> ---------------------------------------------------------------------------
>
> ----- Original Message ----- From: "E.P. Grondine"
> <epgrondine at yahoo.com>
> To: <meteorite-list at meteoritecentral.com>; "ACC Bill Allen"
> <ballen at hohmanntransfer.com>; "Astronomer" <meb at star.arm.ac.uk>; "Ted
> Bunch" <tbear1 at cableone.net>; <burchar at math.okstate.edu>; "phil burns"
> <pib at pibburns.com>; <c.leroy.ellenberger at wharton.upenn.edu>;
> <cavetank at aol.com>; <dallas at ldeo.columbia.edu>; <dja at star.arm.ac.uk>;
> "Duncan" <duncansteel at grapevine.com.au>; "Leroy Ellenberger"
> <c.leroy at rocketmail.com>; "Richard Firestone" <rbfirestone at lbl.gov>;
> "Richard Firestone" <rbf at lbl.gov>; "keith holsapple"
> <holsapple at aa.washington.edu>; "George Howard"
> <george at restorationsystems.com>; "Elton Jones" <mstreman53 at yahoo.com>;
> "Kennett" <dkennett at uoregon.edu>; "Bob Kobres" <bkobres at uga.edu>;
> "Raoul Lannoy" <raoul.lannoy at pandora.be>; "W. Bruce Masse"
> <wbmasse at lanl.gov>; <napierwm at cardiff.ac.uk>; "bernd pauli"
> <bernd.pauli at paulinet.de>; "Benny Peiser" <benny.peiser at thegwpf.org>;
> "Tree Rings" <m.baillie at qub.ac.uk>; "Peter Schultz"
> <Peter_Schultz at brown.edu>; <tankerkh at uc.edu>; "Oscar Alfredo Turone"
> <oaturone at sinectis.com.ar>; "Sterling K. Webb"
> <sterling_k_webb at sbcglobal.net>; "Allen West" <Allen7633 at aol.com>
> Sent: Tuesday, April 26, 2011 1:32 PM
> Subject: [meteorite-list] KT extinction impacts
>
>
>> Hi all -
>>
>> Ahem.
>>
>> Jay, you are right that it is a hypothesis that the KT impacts were
>> from fragments of the same comet.
>>
>> The other explanation, and a far more likely one, now that you
>> mention it, is that Clube and Napier's injection mechanism was at
>> work, and multiple comets hit at roughly the same time.
>>
>> In this summary, note the pooling of oil in the fractures, which may
>> go a long way toward explaining the lack of public publications:
>>
>> http://starmon.com/KT_craters.html
>>
>> http://bi154.dhcp.ttu.edu/extinction/chatterjee+rudra08.pdf
>>
>> It is also interesting that 41 major scientists signed an open letter
>> declaring that Chicxulub caused the extinction of the dinosaurs
>> shortly before Chatterjee's work was widely circulated.
>>
>> In doing this they followed me in the earlier mistake I made in
>> responding to Keller's nonsense several years earlier.
>>
>> In answer to the nuclear effects of hypervelocity impacts, it appears
>> that photons in the reaction reach an energy level capable of
>> splitting neutrons (nucleons) into neutrons and protons, resulting in
>> higher 10 Berylium and 14 Carbon levels. Even in impacts much smaller
>> than these.
>>
>> (Sterling, do you have a public formula handy for converting craters
>> into megatons in a very rough number? Anything better than the Purdue
>> online impact simulator? I have misplaced my Excel spreadsheet.
>> Stroke.
>>
>> Can you also speak to the issue of the energy in the 10Be/14C
>> production?
>> Is it a fission addition, or a fission subtraction?)
>>
>> By the way, there is a special on my book "Man and Impact in the
>> Americas" over at the cosmictusk.com.
>>
>> E.P. Grondine
>> Man and Impact in the Americas
>>
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Received on Wed 27 Apr 2011 08:06:49 PM PDT