[meteorite-list] Newbie with questions

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 16 Jun 2010 19:22:29 -0500
Message-ID: <DB175128667243FFA707F09BA8E9D815_at_ATARIENGINE2>

Hi, Chris, List,

I'll answer one of those questions:

> how big does a fragment have to be
> in order to be visible...?

You're not seeing the fragment itself; you're seeing
the ball of incandescent gas and plasma that surrounds
it. If you see a meteor from some annual shower like
the Perseids, you're seeing the luminous plasma
that is generated by something no bigger than a
pea (maybe less).

And you're also seeing it because it emits light. Afterall,
we can "see" a star without seeing an extended disc. Only
the biggest telescopes can resolve the tiny disc of a giant
star. Even a ball of plasma is is just a point of light at
distance. When someone says of a bolide, "It was BIG,
really big!" it usually means, "It was really bright."

Fireball videos that seem to show a "big ball" are
only showing an area where their sensors overloaded.
The same is true of a human eyeball adjusted to the
dark.


Sterling K. Webb
(Not a Wisconsinite, but
lived there for 15 years)
---------------------------------------------------------------------------
----- Original Message -----
From: "Chris Pagel" <catdoc at gmail.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Wednesday, June 16, 2010 6:21 PM
Subject: Re: [meteorite-list] Newbie with questions


Ahoy, meteorite list. I've only been lurking the forums since after
the Wisconsin fireball.

I'm a native Wisconsinite. I live an hour from the debris field. I
witnessed the descent and fireball from 40 miles away with no
obstructions and with totally dark skies over farm fields. I wouldn't
trade the memory of those 6 seconds for any pieces. This was the
fourth bolide I've personally witnessed in Wisconsin in 25 years;
maybe we are the new NWA, with better beer and cheese?

I am happy to have found a piece on my own, a beautiful 9gm oriented
spear-point with lipping, and have purchased 4 others (3 whole, one
slice). You may have seen my hand-made flyers in the area. I'm going
to loan the fragments I have to the UW Geology Museum for display, and
possibly elsewhere in the state's museums. I laud the display being
put together for the Iowa-Grant Schools.

The debris field map that I used in searching is at:
http://wisconsinfireball.com/strewnfield.html
The pages were written by a fellow Wisconsinite (never heard 'Sconnie
before a year ago). Seems like a nice guy.

Some Questions for the collective:

A) Has anyone timed the "flash-flash" off the various cameras and
spaced the approximate "center" of the two initial debris field
clusters to determine the speed at detonation of the WI fireball?
What is it usually?

B) I witnessed the explosions and fragmentation. Now, I worked in a
pet store in the long-long ago, and experience counting crickets and
goldfish on the fly gives me confidence that I saw 10 to 15 fragments
of varying brightness go from white to yellow to orange to red to dark
flight. Very, very flat flight.

Not to sound like a high-school physics question, but from all your
various experiences interviewing eye-witnesses pan-globally:

>From exactly forty miles away, how big does a fragment have to be in
order to be visible to 41-year old eyes, pupils adjusted for
night-time driving conditions, but witnessed in dark-sky conditions?
Dust, Pea, Fist, Basketball, Car Engine, All of the Above, None of the
Above. Choose all that apply.

C) How long does it take for the fusion crust to disintegrate off a
buried meteorite in wet earth and freeze-thaw cycles? What should I be
looking for over the years? Any links to pics in your collections?

D) One of the pieces I have is a lovely end-cut. The wet-saw technique
developed rust spots amongst the matrix. Is there anything to be done?
It is hard to even write this sentence, but is this rust possibly
shallow enough to sand away with 600 grit sandpaper using a sheet of
glass for flatness?

E) Storage: where do you folks find dessicants to prevent further rust?

Thanks for your time, I look forward to any variety of input or
responses.

-Chris
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Received on Wed 16 Jun 2010 08:22:29 PM PDT