[meteorite-list] Dumb Questions About Meteors & Meteorites

From: Meteorites USA <eric_at_meteoritecentral.com>
Date: Mon, 25 Jan 2010 19:26:20 -0800
Message-ID: <4B5E60DC.6080905_at_meteoritesusa.com>

Hi Everyone,

I'm not too sure how to broach the subject without stepping on toes, so
I say this will all due respect to everyone who would be offended by the
questions.

I've been reading "Meteorites" by Caroline Smith, Sara Russell, and
Gretchen Benedix, Firefly Books, 2009. Lovely book, with lots of
information on meteorites, their origins, and composition, with loads of
illustrations and great photography.

As I was flipping through I found a mention about the total weight of
meteoritic material which falls on our planet every year. On page 89 it
states "...approximately 40,000-60,000 t of extraterrestrial material
lands on Earth every year, the majority of which is in the form of tiny
dust grains usually less than 1 mm (1/25 in) in size; importantly, most
of this dust is believed to originate from comets..."

Doesn't this go against what science tells us about meteor showers?
Don't the particles and sand-grain sized particles burn up in the
atmosphere like science tells us they do? And if they don't burn up
completely why does just about every text on meteors say they do? And if
that the case, then how is it possible to weigh something that doesn't
exist, anymore?

I've read this in other places as well, some sources say that there is
thousands of tons to millions of tons of meteoritic material landing on
Earth every year. Yet...

We all "know" that small dust to sand grain sized particles burn up high
in the atmosphere, and there is debate on what it takes, or rather how
large meteoroids must be to reach the ground and become meteorites. We
know Asteroid 2008 TC3 was small but much larger than dust. So if a 3-6
meter asteroid can hit Earth, how small of a piece of debris can make it
to Earth through the atmosphere? How big was Whetstone Mountain before
entering our atmosphere? There was not much of that piece recovered, and
the video showed 3 distinct fragments flying briefly through the field
of view of the camera. West Texas was a daylight fireball seen from
hundreds of miles away, and it produced a good bit of material. Buzzard
Coulee too. These recent meteorite falls have been hunted by a large
number of very professional meteorite hunters and scientists and yet the
TKW of the falls are small except maybe the BC fall. Buzzard Coulee had
a HUGE 13 kilo piece
http://www.skyriver.ca/astro/bruce/marsden_meteorite%205.JPG that
impacted the ground and hundreds of other smaller stones recovered.

So how big "does" a meteoroid have to be to reach the ground? Do we
really know?

Regards,
Eric Wichman
Meteorites USA
Received on Mon 25 Jan 2010 10:26:20 PM PST