[meteorite-list] How much survives entry?

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 3 Dec 2009 23:08:20 -0600
Message-ID: <CC9A528A36C34B1C9E692DAD3E6F6A3B_at_ATARIENGINE2>

There's a semantic tweak to whatever answer
is given. We presume on good evidence that
many meteoroids result in no meteorite at all
reaching the Earth. That is our assumption,
at any rate. In that case, the loss is... 100%

So, when we ask "how much of an ordinary
chondrite is lost," are we restricting the average
loss figure to only those meteoroids that produce
(or seem likely to have produced) a meteorite?
Do we leave out the class of 100%-loss meteoroids?
A bit awkward, as they may well outnumber the
meteorite-producing objects. I would say they do.

The best answers are estimates. (An estimate is
a computer model without any mathematics.) Richard
Norton said 90% was a minimum figure for ablative
loss. Chris just posted an estimate of 95% to 99%
ablative loss for meteorite-producing meteoroids.
We tend, sometimes unconsciously, to speak only
of the meteorite-producing meteoroids. I would
say that any loss less than 100% is remarkable
(and good fortune).

2008TC3 at 2 to 5 meters diameter must have
weighed between 10 and 150 metric tons. The
four kilos recovered would suggest a minimum
loss of 99.96%. Of course, there could just as
easily been 40 kilos of which only 10% was
recovered (99.6% loss). Or 400 kilos of which
only 1% was recovered (96% loss).

I think it unlikely there was 400 kilos reaching
the ground, but quite possible there were 40 kilos.
(Most likely fall weight would be 15 to 25 kilos.)
I don't think all of it was recovered. Strewn fields a
century old still yield up meteorites today. These
loss estimates are based on that lowest weight
estimate of ten tons... At an original 100 metric
tons, the losses would be an order of magnitude
higher.

Now that we've proved that meteorites are
impossible, well, ALMOST impossible, we can
say that to produce one must require something
odd about the original meteoroid --- low entry
velocity, shallow entry angle, an unusually
aerodynamic shape, or some combination of
infrequent factors.

2008TC3 had two of those characteristics.
Entry velocity was only 1600 m/s over the
Earth's escape velocity and the entry angle
was only 19 degrees above the local horizon.
It beat the odds and reached the ground,
but it paid at least a 99.9% tax to do it!


Sterling K. Webb
----------------------------------------------------------------------
----- Original Message -----
From: "Richard Kowalski" <damoclid at yahoo.com>
To: "meteorite list" <meteorite-list at meteoritecentral.com>
Sent: Thursday, December 03, 2009 6:45 PM
Subject: [meteorite-list] How much survives entry?


> Does anyone have a rough estimate on how much material, say ordinary
> chondrite, is lost during entry? 80% converted to light, heat and
> dust? 90%? 99.9%?
>
> Thanks
>
> --
> Richard Kowalski
> http://fullmoonphotography.net
> IMCA #1081
>
>
>
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Received on Fri 04 Dec 2009 12:08:20 AM PST