[meteorite-list] How much survives entry?

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 4 Dec 2009 15:36:22 -0600
Message-ID: <455822B5668D44FEB184DE18A875BF53_at_ATARIENGINE2>

Hi, All,

Chris said:
> If you are asking how much of a meteorite's
> parent body was lost, there's no problem; it's
> never 100%. It is only in asking how much of a
> meteoroid survives ablation that you have to deal
> with the fact that it's usually 0%.

That encapsulates two ways of looking at this question.
One is to discuss a specific meteoroid / meteorite
and try to deduce the specific results. The other
way is as a general question concerning the entire
CLASS of meteoroids / meteorites. I took the question
in the general sense. Taxonomy, in other words.

And, just as in all natural science, there is considerable
variation in individuals and the conditions of re-entry.
A plasma jet experiment will tell you ablation rates
for various speeds on a specific or generalized material,
but practically, this only provides broad boundaries to
the problem. Very broad boundaries, because of the
variances in speed, duration and the character of the
material being ablated.

If, for example 2003TC3 had entered at 45 degrees
to the horizon at an encounter velocity of 27,500 m/s,
I can practically guarantee you nothing would have
reached the ground, whether it weighed 10 tons,
100 tons, or 1000 tons.

[In case there are quibbles with this, yes, it would
likely fragment at high altitude, but the fragments
would be moving faster than 12,000 m/s and would
never withstand ablation long enough to hit. I also
did the calculation for both shallow entries and
high-angle entries at this speed and the result is
the same. Speed kills.]

There are so many possible events that an empirical
general answer can probably only be reached by the
long-term continued operation of fireball tracking
networks. So far, they suggest many meteoroids and
far fewer meteorites.



Sterling K. Webb
--------------------------------------------------------------------------
----- Original Message -----
From: "Richard Kowalski" <damoclid at yahoo.com>
To: "meteorite list" <meteorite-list at meteoritecentral.com>; "Sterling K.
Webb" <sterling_k_webb at sbcglobal.net>
Sent: Friday, December 04, 2009 2:42 PM
Subject: Re: [meteorite-list] How much survives entry?


> Sorry for my poorly formed query.
> I certainly did not mean that we'd include meteoroids that were so
> small that they completely burned up before becoming meteorites on the
> surface. I figured that was a given.
>
> My mistake.
>
> Yes and I did try to be a bit subtle in my query and ask about an
> ordinary chondrite instead of an Ureilite just to make the back of the
> envelope calculations easier. I am assuming someone somewhere has
> tested actual chondritic material in a hypersonic plasma tunnel to
> measure the exact amount of ablation and possibly someone here knew
> that result. That way it wouldn't be a guess but an actual
> measurement. Now that I've thought about it some more I know someone
> who may have already performed that experiment, so I'll contact him...
>
> Too me, 99.9% seems to me to be an excessive amount of loss due to
> ablation and disintegration, but maybe I'm wrong. Anyway, even if you
> use that number, with 2008 TC3 "weighing" an estimated 72,600 kilos
> before entry. 99.9% loss would mean there is still about 65 kilos of
> material on the ground in the Sudan that has not yet been recovered.
>
> --
> Richard Kowalski
> http://fullmoonphotography.net
> IMCA #1081
>
>
>
>
Received on Fri 04 Dec 2009 04:36:22 PM PST