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Re: Extinction scenarios




James R. Cunningham wrote:

> PTJN@aol.com wrote:
>
> > In a message dated 8/14/98 10:33:05 AM Eastern Daylight Time,
> > jrccea@bellsouth.net writes:
> >
> > << I've e-mailed Stanley Schmidt for permission to xerox the 1966 Enever
> > article (and >>
> >
> > Jim,
> >
> > I think this is very interesting, and I would like to see Schmidt's original
> > article reprinted.  But the caveats are valid.  On global scales, the
> > curvature of the earth itself would limit the immediate effects of radiant
> > energy from the impact itself (light, infrared heat and ionizing radiation) 
> > to
> > "line of sight" exposure.  Equalizing those energies over the globe by
> > "averaging" them on a "per unit area" basis dramatically overestimate the
> > global effects.  As an engineer, you certainly understand that.  Atmospheric
> > and geophysical vectors are different, of course.
>
> Hi Pat,I agree fully, and commented on it in one or another of my posts.  
> Latent
> heat of evaporation is about the only component of the 'effects' scenario that
> would get almost totally homogenized with time.  I'm well aware that the 'grid
> H-bomb scenario' would wipe out everything on the planet.  It's only 
> usefulness is
> in providing everyone with an image of total impact power that they can relate
> to.  On a more personal note, I myself don't believe the K-T impactor was that
> large (I took the middle of the usual projected diameter range 6-10 miles), I
> don't think it was going that fast (50Kps is an average impactor speed - I
> personally think Chixulub was a slow strike), and I think it was loosely 
> bound,
> all of which would lower the impact energy. If we were to assume the impactor 
> was
> 6 miles in diameter rather than 8, hit at 30Kps rather than 50, and was 
> loosely
> bound rock rather than solid, then the impact energy would be about 19% of my
> posted numbers. But 167 Teratons of TNT is still a healthy explosion. And to 
> be
> totally candid, it's still a guess on my part, and was on Enever's part as 
> well.
> With the caveat that I wouldn't want to assume all parameters are on the same 
> side
> of the mean.
>
> > I'm a little surprised that the planetary geologists don't have a better
> > handle on these issues.
>
> They may.  It isn't my field.
>
> >  I can remember working in Dr. Ron Greeley's lab in
> > 1979 at Arizona State University using Mariner photos and solar angles to
> > calculate Martian crater ejecta blanket thickness and crater rim height for
> > the ASU grad students at the time (A grunt, I think I was called).  These 
> > guys
> > were asking the same questions then!  How much energy was involved in an
> > impact and how was it dispersed?  Is it the paleontological community that 
> > is
> > uninformed about recent work on the issue, or is data from the 60's and 70's
> > (from physicists, engineers or whomever) still the best we have?
>
> I don't know.  I wish I did.  I liked Enever's article because I enjoy good
> predictions and projections, and he did well.
>
> > There MUST
> > be more recent work, particularly given the recent Jovian impacts.
>
> Hopefully there is.  Anyone out there know anyone working in that field?Jim
>
> > Pat Norton