Hi, Eric,
The Earth collects dust. Not just from meteors
and meteoroids burning up in the atmosphere
but directly from space. The Earth gravitationally
collects solar wind particles, zodaical dust,
interplanetary dust, interstellar dust, cometary
dust, dust from a variety of sources. Whoops! I
left out intergalactic dust...
Dust falls in slowly and takes months (or years)
to settle to the surface. It can be measured in the
layers of ocean sediments and icecap cores.
How much dust accumulates is hard to measure,
so the amount has been a long-running question.
Here's a really good discussion of the dust question:
http://www.talkorigins.org/faqs/moon-dust.html
although it's in the context of an "age of the Earth"
argument with Creationists.
Interplanetary dust is hard to analyse because it's so tiny:
http://www.meteoriticalsociety.org/simple_template.cfm?code=resources_dust&CFID=4156261&CFTOKEN=70584526
Here's an interview with Don Brownlee ("Mr. Dust"):
http://euro.astrobio.net/interview/742/extraterrestrial-capture
A good summary of all the kinds of dust from "out there":
http://en.wikipedia.org/wiki/Cosmic_dust
Or, just Google "interplanetary dust" and you will
find many, many sources of information on dust infall:
http://www.google.com/search?hl=en&q=interplanetary+dust+&aq=f&aql=&aqi=&oq=
then Google "interstellar dust" and Google "zodaical dust"
and...
Space is dusty. The Earth is dusty. And best of all,
the Internet is dusty. Lots of information out there.
Best of all, you can collect rainwater, then extract the
metallic dust from it with magnets. Most of the dust will
be human produced smoke dust, but the tiny dull metallic
spheres are probably "cosmic" dust. Every time you walk
out the door, you're stepping on cosmic dust. It's everywhere.
If you spend a fair amount of time out in the open air, you
probably have some cosmic dust incorporated into your body.
I'm going to stop now, before I start singing that Joni
Mitchell song...
Sterling K. Webb
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----- Original Message -----
From: "Meteorites USA" <e...@meteoritesusa.com>
To: "Meteorite-list" <meteorite-list@meteoritecentral.com>
Sent: Monday, January 25, 2010 9:26 PM
Subject: [meteorite-list] Dumb Questions About Meteors & Meteorites
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
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