[meteorite-list] Witnessed fall lunars?

From: almitt2 at localnet.com <almitt2_at_meteoritecentral.com>
Date: Tue, 07 Sep 2010 17:26:52 -0400
Message-ID: <20100907172652.qwvl14jb3ls0kggs_at_webmail.localnet.com>

Hi Dr. Korotev and all,

I appreciate your lunar website and often refer to it. Glad you are a
participant here.

If that is the case then lunar meteorites would have to heat up quite a
little bit due to this slower speed. How altered would material be then
from the fall?
perhaps the ablating process is enough to keep the material relitively
cool with out altering the material significantly.

As the material approaches Earth it should speed up due to gravity.
It's a down hill trip from the moon after a certain point (about 1/3
way toward the Earth).

I've heard only a small percentage actually reaches the Earth due to
physical dynamics. Best!

--AL Mitterling


Quoting Randy Korotev <korotev at wustl.edu>:

>
>> MikeG asks:
>
>> "Is there a theory for why there have been no witnessed falls of lunar
>> meteorites? It seems odd to me that we have 4 Martian witnessed falls
>> (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no
>> lunars."
>
> One issue is that these 5 meteorites are 5 kg, 4 kg, 18 kg, 10 kg,
> and 0.8 kg in mass. Only 3 lunars are >4 kg in mass.
>
> Another issue (probably more important) is that lunar escape velocity
> is only 2.4 km/s and very little material ejected from the Moon is
> going much faster than that. This velocity compares with 20-40 km/s
> for asteroidal meteorites. Is a rock entering the atmosphere at 2.4
> km/s going to noticeably incandesce? I don't know. I believe that
> the space shuttle hits the atmosphere at ~7.7 km/s.
>
> Melanie asks:
>
> "I asked this a while ago on Greg Catterton's forum, and I was told
> that rocks
> from the moon aren't as solid (tough) as Mars rocks, and therefore are less
> likely to survive entry... yet what about all these Howardites?"
>
> Although breccias, most of the lunar meteorites are very tough rocks.
> Any rock that survives being blasted off the Moon isn't going to
> disintegrate in Earth's atmosphere any more than an asteroidal or
> martian meteorite.
>
> Steve says:
> "The moon is close to the earth and material knocked off the moon has
> a relatively short time to reach the earth."
>
> Compared to what? Some lunar meteorites took a million years or more
> to reach Earth.
>
> "Mars is farther away and not protected by a companion and its closer
> to the asteroid belt so it receives many more impacts than the moon."
>
> Not "many more." Only a factor of two greater for Mars, but the
> average velocity of the impactors is only 60% as great.
>
>
>
> Randy Korotev
> Washington University in St. Louis
>
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Received on Tue 07 Sep 2010 05:26:52 PM PDT