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

[Sterling K. Webb]

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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