[meteorite-list] A question????? another answer

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sat, 6 Jun 2009 00:54:43 -0500
Message-ID: <96D59AF663234A21931A29838B2F50B1_at_ATARIENGINE2>

Hi, E and List,

    Bret Gladman's simulations of rocks blasted off
the Earth by impact show about 50% of them being
"re-captured" from independent orbits and returning
as "meteorites." The time scale for re-capture varies
from 10,000 years to 10,000,000 years. So, if there
were any returns from the Ries impactor, they would
already be here, mostly likely.

    Sedimentary meteorites are discussed here:

    Monica Grady, looking for a possible Martian
sedimentary stone, wrote a paper requesting
museums and collections to look for such anomalous
stones as might be found in their dusty drawers or
cabinets in this publication (p. 77):

Sterling K. Webb
----- Original Message -----
From: "Mr EMan" <mstreman53 at yahoo.com>
To: "meteoritelist" <meteorite-list at meteoritecentral.com>
Sent: Friday, June 05, 2009 10:58 PM
Subject: Re: [meteorite-list] A question????? another answer

> You are too kind, Carl. Let me address your questions inside your
> quote:
> --- On Fri, 6/5/09, cdtucson at cox.net <cdtucson at cox.net> wrote:
> Q: I have a few follow-up questions for you; If an Earth meteorite
> (terrene) were to return back to Earth, would we be able to identify
> it correctly?
> A: Yes and No. IF you look at the locations of recent major
> impacts(80 Million years or later) and consider the bedrock/ target
> rock-type at the launch origin. It narrows the filed of possible rock
> types.
> The best candidate is Reis crater in Germany which lies on limestone.
> The Canadian shield cluster and Popogui impacts are far too (old we
> think) and that leaves Chesapeake, Chicxulub, The un-named crater in
> the North Sea off Scotland and Wetumpka Al. So far as I know all
> these excavated down to deep crystalline basement rock so most have a
> component of igneous rock mixed with the sedimentary kinds.
> Statistically the older the impact the more likely that any orbitally
> ejected material will have already fallen back long before mankind
> existed. Someone somewhere did a study of the physics on what sized
> crater had enough energy to eject material at escape velocity and
> seems like it was in the range of 5 miles/8km someone with a better
> database might chime in.
> Chicxulub target rocks included slates,sandstone, sulfate rocks and
> weathered lavas . The sulfates are generally too fragile. Sandstone
> has a wide range of hardness and is more difficult to predict launch
> integrity and space survival. Quartzite remains the best candidate for
> launch, survival and recognition but Popagui in Siberia is over 200
> myo(?)(Geoff Notkin knows, he fed the mosquitoes there one summer).
> The crystalline bedrocks are usually pyroxene, mica, feldspar, and
> silica(quartz) mixtures. Earth rocks tend to have larger grain and
> clast sizes. Certain grain sizes could only come from Earth as no
> other planet other than Venus could grow them.
> That leaves a granitoid rocks and quartzite for best chance of
> survival and recognition. A fusion crust on those: granite --white to
> brown with specs of black. Quartzite probably a frosty clear glass
> coating.
> When Limestone is heated it does not melt but turns into highly
> soluble lime (CaO) and Carbon dioxide ( CO2)...so there isn't a fusion
> crust. It would be white until the first rain.
> Q: That is to say would we not simply ASSume it came from the moon? As
> a
>> moon meteorite would also have Earth air or isotopes?
> A: Owing that the Earth and Moon came from the same stock we share the
> same isotope abundances so there is no isotope ratio test to
> differentiate them. Again grain size and clast sizes would be larger
> on material from Earth
> We make new supposed Lunar meteorite discoveries with new
>> materials all the time. So again I ask is there a way to be
>> certain where it came from? I ask because if is not mostly
>> plagioclase, it seems to me most investigators would simply
>> toss it aside and say; it is not a meteorite, that is a rind
>> or weathered Earth rock not fusion crust.
> Yes there is so much industrial slag about even regular moon
> meteorites look like it but I will keep looking for out of place
> rocks. Moon material from the Mares is hard to differentiate from
> earth basalt save for the clasts. The feldspars could come from
> anywhere in New Hampshire, Vermont-- actually most all of New England,
> so again anyone looking would need a very trained eye. I think the
> first identified Earthite will be the one that crashes through a roof
> and makes someone take a hard look.
> Right now unless it were very very old due to an extremely large orbit
> that took 700-1300 million years to decay-- there are no candidate
> craters on Earth that are in feldspar-rich bedrock that come to mind.
> Actually Nininger(?) or someone--found a limestone object that was
> reported to be a fall and in fact he thought it to be a meteorite but
> it was so unlike anything known it was unable to prove it. The
> where-a-bouts of the object is unknown. It is listed as a
> psuedo-meteorite in the Natural History (British) Museum's Catalog of
> meteorites
> Q: So, another
>> question would be this; if it clearly has a fusion crust
>> complete with the gas bubbles would there be a way to prove
>> it is in fact a genuine fusion crust???
> The short answer: Cosmic ray tracks and enriched tritium from solar
> wind would be proof that the material had been in space. Fusion crust
> in my book is over rated as "proof" owing to the wide occurrence of
> industrial glass so widely spread on Earth AND poorly
> understood/recognized accurately as everyone claims fusion crust when
> in fact the crust is long gone and they are looking at the ablation
> surface. An ablation surface can look like water or wind-worn
> surfaces.
> You are Welcome, Elton
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Received on Sat 06 Jun 2009 01:54:43 AM PDT

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