[meteorite-list] Dumb Questions About Meteors & Meteorites

From: Robert Woolard <meteoritefinder_at_meteoritecentral.com>
Date: Mon, 25 Jan 2010 20:57:56 -0800 (PST)
Message-ID: <461264.43464.qm_at_web39606.mail.mud.yahoo.com>

Hello Eric,

? I'm very sure others on the List will supply you with much better info in short order, but here are 3 quick "quotes" I found that states that very tiny micrometeorites make it through the atmosphere without burning up. I've read better explanations (it involves the ratio of surface area to weight) but I can't find it right now. Like I said, I know others will explain it better, but perhaps this will be of some interest to you:

1. A meteor, or shooting star is produced by the heating and vaporization of meteoroids which enter earth's atmosphere at high speeds. Most are about the size of a grain of sand. An average of about six per hour can be seen by a patient observer on a clear night. Several times as many may be seen during a meteor shower, when the earth encounters a swarm of meteoroids.


2. Meteorites are the remains of meteoroids which were large enough to survive the trip through the atmosphere, and thus reach the ground after a fiery descent. Micrometeorites are so small that they slow down before burning up, and land gently as dust particles.

3. Small meteors (about 1--10 grams in mass down to almost a nanogram (0.000000001 gram)) burn up in the Earth?s atmosphere before reaching the ground. Extremely small-sized particles (very fine dust) can make it through the atmosphere unmelted. Meteors larger than about 10 grams are partly melted, but the interior reaches Earth?s surface intact.


? Best wishes,
? Robert Woolard
 
--- On Mon, 1/25/10, Meteorites USA <eric at meteoritesusa.com> wrote:

> From: Meteorites USA <eric at meteoritesusa.com>
> Subject: [meteorite-list] Dumb Questions About Meteors & Meteorites
> To: "Meteorite-list" <meteorite-list at meteoritecentral.com>
> Date: Monday, January 25, 2010, 9:26 PM
> 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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Received on Mon 25 Jan 2010 11:57:56 PM PST