[meteorite-list] Trying again...

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 09:52:06 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4E2A9_at_US-Torrance.mail.saic.com>

Hi List,

I sent this to Met-Central twice yesterday -- evidently no posts
were making it through. Trying again...

-----Original Message-----
From: Matson, Robert
Sent: Tuesday, August 06, 2002 10:11 AM
To: 'John Reed'; David Freeman
Cc: meteorite-list_at_meteoritecentral.com
Subject: Going hunting

Hi John, Dave and List,

John, I remember you asking me (or perhaps it was the list) about this
sighting before, and my advice was pretty much the same as Dave
Freeman's this morning: you have a better chance of finding a
different meteorite than any potential meteorite that might have
been produced by whatever you observed/heard more than 15 years
ago. There are a few facts that you will need to resolve in your
attempt to reconstruct events. For example, there is a physics
problem with your following statement:

"...the fire ball part only lasted a split second when I saw it
in the sky then it was probably close to 2 seconds before I heard
it chopping the wind then I saw a big blur of grayish fuzz and a
quick shadow passing over."

These events cannot all be related to one another. Fireballs usually
cease to be incandescent at altitudes over 20 km -- often quite a
bit higher than this. On rare occasions, large objects can penetrate
further (say, to 15 km) before they begin "dark flight". But in
any case, dark flight lasts MINUTES, not seconds. I doubt anyone
has ever both seen a bolide and dark flight of that same bolide --
minutes later. Of course, REALLY large objects don't ever slow
down enough to have dark flight -- but if you saw one of these,
you wouldn't be alive to tell us about it. ;-)

On a more positive note, the man-hours required to find a new meteorite
aren't nearly as bad as the 800 man-hour figure that Dave mentioned --
provided you're smart about where and how you decide to spend those
search hours. (The bayous of Louisiana are clearly a poor choice, but
any heavily vegetated area or a region with a lot of dark rocks is
going to severely hamper your efforts.) Forget about a metal detector;
this may be helpful AFTER you've made an initial find, but one will
only slow you down while trying to make that first find. You can
cover much more ground with your eyes.

So how long can you expect to search before making a find? Depends
on where you go, your recognition skills, and a lot on luck. I made
my first find after 40 hours of searching, and I was looking exclusively
on desert dry lakes. I'm embarrassed today by some of the rocks I
brought home on those early trips, so be aware of the steep learning
curve. Don't expect to find anything in your first 20 hours --
recognizing weathered meteorites in the field is definitely an
acquired skill. In time you learn to recognize all the meteorite
look-a-likes ("meteorwrongs") indigenous to your area, and so you'll
waste less and less time on these terrestrial rocks.

Today (after nearly 350 hours of active search time), I can expect to
make a new find about every 12-15 hours, though it's getting harder
to get to places that I haven't previously visited. (If I just want
to find ~any~ meteorite or meteorite fragment, there are places I
can go that will only require 6 hours per find on average).

The desert around Palm Springs is not a bad place to look, though you'll
have to contend with sage brush and other sparse vegetation which will
hinder your viewing, requiring you to walk much closer to a meteorite
before you'll spot it. I'd suggest dry lakes as an alternative, except
that just about every dry lake within 200 miles of you has been searched
by multiple people, multiple times. Wherever you decide to look, I
wish you the best of luck. And one final bit of advice: take a
weathered, brown chondrite along with you to use as a search image.
After you spend hours picking up dark brown and black terrestrial rocks,
you'll forget what you're looking for!

Cheers,
Rob
Received on Wed 07 Aug 2002 12:30:22 PM PDT