[meteorite-list] L chondrites vs. H and LL

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:28 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4EE18_at_US-Torrance.mail.saic.com>

Hi All,

I spent some more time exploring the statistics of equilibrated
ordinary chondrite recoveries from Antarctica, and discovered an
oddity in the mass histogram for L-chondrites:

http://members.cox.net/mojave_meteorites/Antarctic_Histogram.jpg

Notice the dip in L-chondrite masses between 10 and 100 grams.
By comparison, the histograms for H- and LL-chondrites look more
like what one would expect: going from right to left, a steadily
increasing number of finds as the masses decrease to about
10 grams, with a drop off below this mass due to the difficulty
in spotting small meteorites.

In addition, the median mass is noticeably higher for L- chondrites
than either H- or LL-chondrites:

 H median mass = 17.78 g
 L median mass = 82.90 g **
LL median mass = 22.81 g

What does this imply about L-chondrites? Are they sturdier than
H's or LL's? If so, does the greater robustness come into play
during atmospheric entry, or while weathering on the ground, or
a combination of the two?

Or perhaps it's due to orbital dynamics -- maybe the post-impact
orbit(s) of the L parent body fragments have a lower cosmic
velocity than those of H's or LL's, exposing them to less stress
during passage through earth's atmosphere?

Or could it be a visibility issue? Are L's for some reason
harder to spot than H's or LL's, making smaller finds less
likely? The double hump of the L histogram suggests this
isn't very likely.

Perhaps some of you have some other possibilities in mind.

Cheers,
Rob
Received on Tue 14 Oct 2003 06:17:03 PM PDT