[meteorite-list] Further thoughts

Thu Mar 20 04:36:48 EDT 2008

Hi Chris, Bob, Listees,

Just to expand a little on what Chris says (he speaks from a great deal 
of observational experience), Bob, let's pose a few thoughts for 
indirect musing...

If meteorites had volatiles that were subject to violent expansions, 
why don't all potential meteorites just turn into powder blasts?  It is 
plausible that this happens to some cometary particles, btw.

Think of where and how the meteoroid formed that is responsible for the 
'rites in our collections.  If it has chondrules, for example, which 
have metamorphized even slightly due to thermal effects - do you think 
it has been hotter at some point in its "life" considering the Earth's 
atmosphere never alters the matrix (insides) of the meteorites we 
recover?  Not only has it been hotter - but it also was formed at low 
pressure if it is a chondrite.  Why can we say the latter?  If it 
formed hot and relatively low pressure or space, would there be many 
volitiles?

Which are the meteorites represented in our collections that are 
chondrites and thermally altered?
H3.X (X>0), H4, H5, H6, "H7". L3.X(X>0), L4, L5, L6, "L7"
Feldspar formed from glasses is a common component in these meteorites 
- at what temperature does this reaction begin to occur?  Indeed - they 
are mostly thought to have formed between 500 and 900 degres 
CENTIGRADE, a range which which reaches over 1650 F.

If they are achondrites, what can we say?  How did they get that way?  
By melting and essentially a process of sedimention + a little 
crystalization now and then?  How hot do we need to be to melt 
silicates? HOT!  Same story, but even hotter for the iron melt that 
leads to irons.  If the silicates separated in this differentiation - 
do you suspect the gasses mostly did and bubbled out too?

So what does that leave?  Mostly a few carbonaceous things that carry 
water, amino acids and boozes.  Let's say we instantly dropped a few of 
them in an oven at 3000 C.  They are just rocks.  Do you think they 
would blow up and hurl pieces in all directions and dent the insides of 
the oven from impacts?  Or would they likely just form fissures where 
any volitile would just slither out of the nooks and cranies and cracks 
saying "psssstttt"?

Jim has written of the "blow torch" test of a tektite.  If something 
looks like a tektite but he isn't sure, he puts it under a real hot 
torch.  Obsidian turns into Pumice complete with pores and fissures. 
(tektites usually don't).While safety glasses would be a good idea, the 
rocks don't turn into firecrackers. (Though I heard certain petrified 
wood rocks from Texas provide entertainment to pyros and explosive nuts 
if you like this thought).

How far do you think a rock splitting open would hurl all the 
fragments?  Especially if it is going over 10,000 mph forward?  If we 
could really make decent bombs by just heating rocks to 3000 degrees, 
the military certainly has been wasting a lot of R&D money"-)

All the above hypotheses ignore whay Chris has pointed out.  "Ablation 
is a very efficient process."  Even in irons which conducrt heat really 
well, we have quite shallow heat affected zones.  I completely agree 
with Chris, though I would prefer to say that 10,000 mph breath cools 
down the porridge quickly.  How could a hot liquid persist so long on a 
slippery surface at that speed?  Ablation therefore can be seen to be a 
surface phenomenon in meteorite after meteorite by just looking at the 
thickness of the fusion rind.

Chris' comments are also right on regarding the temperatures of 
meteoroids in space (and he is assuming they are in Sunlight at about 1 
AU).  Here's a foolish comment of mine to think about.  Did you by 
chance see an old Star Trek episode called "For the World is Hollow and 
I have Touched the Sky"?  Do you think a mesosiderite with eucrite 
inclusions named Yonada at 1 AU would be an mild temperatured world to 
hollow out and and spend some time in a pinch (but not a nova)?  I 
do...Natira, dear?

Best wishes and good health,
Doug

-----Original Message-----
From: Chris Peterson <clp at alumni.caltech.edu>
To: Meteorite-list at meteoritecentral.com
Sent: Wed, 19 Mar 2008 11:53 pm
Subject: Re: [meteorite-list] Further thoughts

Hi Bob- 

Even small meteoroids don't heat up inside during their brief meteor 
phase. Ablation is simply too efficient at carrying away heat. Also, 
it's doubtful any significant gas pockets exist in meteoroids. 

There are quite a few videos of meteors breaking up, and they don't 
seem to show anything like true explosions. I've recorded perhaps 100 
events bright enough to show fragmentation, and the fragments always 
appear to continue along substantially the same path. 

BTW, the space environment isn't particularly cold. The interior of 
meteoroids varies from tens of degrees below freezing to tens of 
degrees above. 

Chris 

***************************************** 
Chris L Peterson 
Cloudbait Observatory 
http://www.cloudbait.com 

----- Original Message ----- From: "Bob Loeffler" <bobl at peaktopeak.com> 
To: <Meteorite-list at meteoritecentral.com> 
Sent: Wednesday, March 19, 2008 11:42 PM 
Subject: Re: [meteorite-list] Further thoughts 

Hi mexicodoug, et al, 

Does anyone have evidence of what really happens (i.e. explode or 
fragment) 
with meteors/meteoroids that pass through the atmosphere? I'm a newbie 
and 
therefore not pretending to know what I'm talking about, but it would 
seem 
to me that there are some meteors/meteroids that COULD have gases 
trapped in 
their molecular structure that COULD heat up and actually explode 
during 
their fiery passage through our atmosphere. Large meteors wouldn't do 
this 
because their internal temperatures never increase at all (they are 
still as 
cold as the space environment where they have been traveling for eons), 
but 
small friable meteors like Carancas could possibly have gases in them 
that 
could heat up and therefore explode in our atmosphere. 

That is just a guess, not a fact, so please no flames. ;-) I'm just 
trying 
to get these ideas out of my head and get some explanations for them. 

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