[meteorite-list] Earth Impactors and Meteor Crater

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:00:10 2004
Message-ID: <3D3FB444.2C13068A_at_lehrer.uni-karlsruhe.de>

Hello All,

Walter wrote:

> Hello Everyone, I have been asked a question for which I have no
> answer. "how large does an object have to be for it not to vaporize
> completely upon plunging through Earth's atmosphere, i.e., for there
> to be anything sizeable left to cause wide destruction once it hits
> the ground (or water)?" I know that the answer is not an easy one
> and there are numerous variables involved (e.g., type of material
> involved, angle of entry, definition of "wide destruction," etc.)
> but does anyone have a guess (or a SWAG) as to the answer.

I would like to draw your attention to R. Norton's CEM (Cambridge
Encyclopedia of Meteorites), especially pp. 39-45: "Meteoroids to
meteorites: a lesson in survival" and furthermore, pp. 49-50, where
you'll find useful information on the sizes of meteorites and their
chances of survival.

Those among us who are lucky enough to own the Buchwald
trilogy, will find a lot of useful information in chapters 1-4:

Chapter 1: The Minor Bodies of the Solar System
Chapter 2: Physics of the Fall
Chapter 3: On Multiple Falls: End Point Height
            and Sound Phenomena
Chapter 4: Meteorite Craters

And I would like to remind you of the famous graphs from Heide
(1964). You also find them in R. Norton's RFS II, pp. 49-53:

- The Ablation Process
- Mass Loss
- Effects of Impact

and again, in CEM, pp. 33-34:

- Meteoroid velocity
- Atmospheric drag

or you can also find pertinent info in the introductory chapter
of McSween's "Meteorites and Their Parent Planets", p. 15 ff.:

=> A Fiery Passage (with the same graph on p. 17, figure 1.9).


Rob Matson wrote:

> wasn't the iron that created Meteor Crater
> estimated to be about 150 meters in diameter?

RODDY D.J. and SHOEMAKER E.M. (1995) Meteor Crater:
Summary of impact conditions (Meteoritics 30-5, 1995, 567):

" ... the meteorite had a velocity in the range of about 13
to 20 km/s, probably in the lower part of this range ...,
the coherent meteorite diameter is estimated to have been
45-50 m with a mass of 300,000 - 400,000 t, i.e., large
enough to experience less than 1% in both mass ablation
and velocity deceleration.


Best wishes,

Bernd
Received on Thu 25 Jul 2002 04:18:12 AM PDT