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

Sat Jun 6 01:54:43 EDT 2009

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:
http://meteorite-identification.com/mwnews/BLECKENSTAD.htm

    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):
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19960027473_1996032004.pdf

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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