[meteorite-list] Vesta and its core.

From: Shawn Alan <photophlow_at_meteoritecentral.com>
Date: Sat, 24 Jul 2010 00:21:57 -0700 (PDT)
Message-ID: <387492.79810.qm_at_web35402.mail.mud.yahoo.com>

Ok so if you weren't addressing Angrites in the first place with Vesta I am going to change the subject to Vesta and its core
?
Now you say that Vesta's core volume is roughly 17%?and?Earth is roughly 17% as well. This being said,?at 2.35 A.U. Vesta?wouldn?t?be able?to attain an iron core at the volume at that distance, concluding to you, that Vesta accreted closer to the Sun. Ill refresh your memory what you said in your previous post.....
?
?"If there is only enough available iron
at 1.5 AU for Mars to accumulate a core that is only
8% of its volume), how could Vesta, at 2.35 AU, have
accumulated enough iron for a core 17.5% of its
volume, or 56% of its original, uncratered diameter?"
?
Simple.... Vesta is only 300 miles in diameter; Earth?s?core is the size of the moon. Vestas core has been suggested to be at 130 miles. So to obtain iron wouldn?t take much compared to Earth core.
?
My guess is this:
?
Abstract:
?
Geological History of Asteroid 4 Vesta:
The ?Smallest Terrestrial Planet?
?
Klaus Keil
?
Taking
into account the somewhat uncertain radial heterogeneity
in 53Mn in the formation regions, these ages can be
used to translate the 53Mn-53Cr formation intervals of eucrites
into an absolute age for the differentiation of Vesta.
Based on measurements of the basaltic eucrite Chervony
Kut, for example, an age of 4563.6 ? 0.9 Ma is derived, only
a few million years younger than the formation of CAIs
(Lugmair and Shukolyukov, 1998). Furthermore, the great
antiquity of the eucrites and hence the evidence for melting
and differentiation of Vesta on a timescale of a few million
years is further supported by the detection of the decay
products of other extinct radionuclides such as 26Mg from
the decay of 26Al (half-life 0.73 m.y.) (Srinivasan et al.,
1999; Nyquist et al., 2001) and 60Ni from the decay of 60Fe
(half-life 1.5 m.y.) (see references in Carlson and Lugmair,
2000)....
?
Modeling of the thermal history of Vesta by Ghosh
and McSween (1998) suggests that heating by 26Al would
keep the mantle hot for ~100 m.y., consistent with the
younger ages of cumulate eucrites....
?
There is convincing geochemical evidence that Vesta
experienced a high degree of (or possibly complete) melting
that resulted in the formation of a metal core. For example,
the depletion in moderately siderophile incompatible
elements (e.g., Ni, Co, Mo, W, P) relative to nonsiderophile
incompatible elements in HED meteorites suggests metal
segregation and hence core formation (e.g., Hewins and
Newsom, 1988, and references therein; Righter and Drake,
1997). However, estimates of the amount of metal in Vesta
vary widely between 0 and 50 wt% (see references in
Ruzicka et al., 1997). For example, Ruzicka et al. (1997)
estimated the mass of the core by mass balance from the
density of Vesta and the density of the silicate fraction to
be between ~0 and 25 wt%, with the best estimate being
~5 wt%. They also suggested that the core is <130 km in
radius, the olivine-rich mantle is ~65?220 km thick, the
lower crustal diogenite unit is ~12?43 km thick, and the
upper crustal eucrite unit is ~23?42 km thick. Dreibus et al.
(1997) estimated the mass of the core from their calculated
composition of the bulk silicate portion of Vesta (assuming
CI abundances for Fe and Ni) to be 21.7 wt%. They
also calculated the density of the mantle to be 3400 kg/m3
and, with a core density of 7900 kg/m3, calculated the bulk
density of Vesta to be 3800 kg/m3, in good agreement with
the astronomically determined values (see above). With a
radius of 263 km and a core mass of 21.7 wt%, they calculated
a core radius of 123 km.
?
http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3034.pdf
?
26AI has been brought up in many papers to explain differentiation among parent bodys and not to mention, Vesta. I like your take on how you think Vesta might have formed, but I find it very odd that you have no scientific articles that relate to Vesta and how you think?Vesta formed in a different part of the solar system. I am also at loss with?your reasoning of Earths, Mars, and Vestas volume to ratio to the core size. Vesta is 300 miles in diameter making the core a mere 100 miles in diameter if that and Earths iron core the size of the moon. But again the core is speculative and we won?t know till Dawn goes by in Aug 2011. But all I know is that 26AI is a great candidate for differentiation to take place with Vesta and not to mention the scientific research to back up how Vesta came to be.

?
?
Shawn Alan
IMCA 1633
eBaystore
http://shop.ebay.com/photophlow/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p4340




[meteorite-list] Its official! NWA 6291 "The King ofAngrites"forsale - AD
Sterling K. Webb sterling_k_webb at sbcglobal.net
Sat Jul 24 01:28:51 EDT 2010

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Actually, I was not addressing the specific question
of the origin of this angrite (or any angrite), but the
more general problem of the "universal assumption
that every sizeable body in the solar system currently
resides at the same address where it accreted originally."
If things move around, it complicates the picture
considerably.

I used Vesta as an example of a body that can't have
accreted in place. If there is only enough available iron
at 1.5 AU for Mars to accumulate a core that is only
8% of its volume), how could Vesta, at 2.35 AU, have
accumulated enough iron for a core 17.5% of its
volume, or 56% of its original, uncratered diameter?
The Earth has a core of 17% of its volume, or just a
hair less than Vesta. Mercury has a core that's 43%
of its volume. Both the Earth and Mercury have
acquired part-corers from encounters with impactors
though.

Iron is a moderately refractory element. It will be
vaporized in the solar nebula only relatively close
to the Sun. The temperature will drop by the square
of the distance out in the protoplanetary disc and
iron will soon condense into the materials from
which grains will form, get sticky, form particles,
accrete, etc.

How you gonna get that much iron vaporized out at
2.35 AU? The answer to that question is the same one
I gave before: No Way. And for the same reason.

If you want to know what should accrete out there,
you can compare Vesta to Ceres. Ceres is in essentially
the same region as Vesta, at 2.7 AU compared to
Vesta's 2.35. AU. Ceres seems to have no core at all,
although Ceres is certainly large enough to have
differentiated. Ceres likely did accrete in place from
rock and ice, as it is the largest body in the asteroid
zone, six times the volume of the original, uncratered
Vesta.

We can identify Lunar and Martian meteorites only
because we have composition data gathered by humans
and robots. That's the only reason. Without a sample
or a set of readings from Mercury, or Venus, or anywhere,
the means of reasonable proof are absent.

When the Dawn mission gets to Vesta, we will likely
be able to nail down the HED identification with that
body. I quote the mission parameters: "This mission
was designed to verify the basaltic nature of Vesta
inferred both from its reflectance spectrum and from
the composition of the howardite, eucrite and diogenite
meteorites believed to have originated on Vesta."

Failure to find the expected HED terrain on Vesta would
be.... interesting. Dawn will be the first test of the entire
effort to "reason out" parent bodies. It will provide evidence
where they has mostly been speculation.

The paper you cite (by Chambers) is a good summary
of the problems in planetary formation theory. There
are lots of those. I used Vesta as an example because
it's an obvious example of the sort of thing he discusses
in the section on "planetary embryos." Vesta would be
at the smallest end of their size range -- not too hard
to toss around.

Until there is evidence enough to settle the question, it
remains speculation. we've had definitions of Science and
of Faith on the List recently. Let me add another one more:
Speculation. Speculation is what you do while you're
waiting for evidence, because there isn't enough evidence
yet for proof.


Sterling K. Webb
-------------------------------------------------------------------------------
----- Original Message -----
From: "Shawn Alan" <photophlow at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Friday, July 23, 2010 10:33 PM
Subject: [meteorite-list] Its official! NWA 6291 "The King
ofAngrites"forsale - AD


Hello Sterling and Listers,

Sterling, thank you for your input about Angrites "might" have a
connection with Mercury by saying Vesta quote un quote......

"Vesta did not .....form where it is. No Way."

Know I am kinda confused with Vesta and your connection or lack of
connection to this topic, but I am going to make an educated guess of
why you might have suggested Vesta in the first place.

This whole topic pulls from Angrites and the possible connections they
might have with Mercury. I am going to zero in on one meteorite, NWA
2999 because it seems that there has been more research done on this
meteorite compared to other Angrites.

One observation of why some scientist feel that NWA 2999 "might" be from
Mercury is that NWA 2999 meteorite has gone through a vertical tectonics
process, which occurs on Earth and Mercury. In addition to this vertical
tectonic process.......

Papike et al. [9]
suggested that angrites might be samples from
Mercury based on volatile depletion, and systematics
of plagioclase compositions and Fe/Mn ratios in
mafic minerals.

http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1344.pdf

Now Sterling, is this the reason why you brought Vesta into this
equation, because its a differentiated body and the vertical tectonic
process might have happened on Vesta? Or its because you feel that Vesta
some how moved from one side of the hood to the other side because of
the iron core being too big for where Vesta is located at?

Lets change the topic and focus on your statement on how you feel about
Vesta, quote un quote ......

"Vesta did not .....form where it is. No Way."


Now this would be a perfect example to use this quote Greg Lindh.......

This reminds me of a quote by Mark Twain. The quote follows:

"There is something fascinating about science. One gets such wholesale
returns of conjecture out of such a trifling investment of fact."

Something to think about....


Iron meteorites tell their own tale. These meteorites
come from asteroids that became hot enough to melt
and differentiate. The most plausible source of heat
was the decay of short-lived isotopes, especially 26Al.
Melting must have occurred while was still abundant,
which means these asteroids took something like 2
Myr to form [19,20]. Why did some asteroids melt
when others did not? Presumably, different stages of
planet and asteroid formation occurred concurrently in
the same region of the nebula. Some objects formed
earlier than others, and their subsequent thermal
evolution was different as a result.

http://groups.csail.mit.edu/mac/users/wisdom/extrasolar/chambers.pdf

I think this pulled abstract could explain your educated guess of why
you think Vesta had accreted somewhere else besides where it is :) My
guess is that when differentiation occured, that with some parent body
the process was more prevalent because there might have been an abundant
amount of 26Al , which this short lived isotope produces alot of heat
which would be a good environment for differentiation to take place aka
in Vesta :) but thats my suggestion and some science to back it up :)




Shawn Alan



[meteorite-list] Its official! NWA 6291 "The King ofAngrites"for sale -
ADSterling K. Webb sterling_k_webb at sbcglobal.net
Thu Jul 22 17:03:44 EDT 2010


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Martin, Jason, Shawn, &c.,

The fly or flaw in the ointment, the paper, and the
responses is an unspoken but apparently universal
assumption that every sizeable body in the solar
system currently resides at the same address where
it accreted originally.

What about a body that accretes in the 0.50 AU block,
then moves 'way up the street and out to the 2.35 AU
neighborhood? Like say, Vesta. Now, I'm not saying
Vesta did that, you know, fled from the 'hood and
moved to the suburbs... I just saying Vesta did not
form where it is.

No Way.

Models that "fit" Vesta propose a iron core of about
http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2129.pdf
300 kilometers out of an original spherical body of
540 km. diameter. Such a body HAS to have accreted
much, much closer to the Sun. I repeat, No Way.

So, isotopic data that tell you where a body accreted
MIGHT tell you everything you need to know about the
place or it MIGHT tell you nothing of any use whatsoever.

Even the old notion about the distribution of iron cores
in the inner solar system is wrong. Decades ago, we
assumed bigger iron cores in close, getting smoothly
smaller as you moved out from the Sun. Then, we
discovered that Venus' core is proportionally much
smaller than the Earth's, and that Mars core is puny.

Then, when we moved to the theory of the Moon being
formed by a giant "impact," or graze, or embrace, all
the models said we had two cores -- our original core
and the core captured from the big proto-Moon. Mercury
too shows evidence of such a collision (although no
moon resulted).

All of a sudden, Venus and Mars have "normal" cores.
The Earth is cheating -- it's packing an extra halfcore
in its hip pocket, and Mercury has two cores-worth of
core. Venus and Mars that are normal respectable planets,
and Earth and Mercury are "core-snatchers."

A simple question like "what should a meteorite from
Mercury be like?" is not a simple question. First, if
Mercury suffered a giant impact early on, then its
present crust (and upper mantle and maybe more)
is derived from the impacting body. And that Big
Whacker accreted... where? Nearby? Faraway?
In-between?

Then, there is the case of a parent body of some
size blasted off the ORIGINAL primordial crust (and
mantle) of Mercury by the giant impact, finding a new
orbit, and providing enigmatic meteorites for the next
billions of years. That original Mercurian crust could
have been quite different from the present crust.

As Jason pointed out, there were a gaggle of large
differentiated bodies in the early system. I go with
the "hundreds" rather than 30-40; see the work by
SwRI that suggests 100+ of them from the inner
solar system ended up in the Asteroid zone. The
Zone is made up of "natives" and a horde of refugees,
which could have accreted pretty much anywhere
and will each have a unique formation history all
their own.

Present arguments are somewhat simple-minded.
It's going to take centuries to sort out the life history
of every body big enough to bother with.

It's going to be fun.


Sterling K. Webb
--------------------------------------------------------------------------------
----- Original Message -----
From: "Martin Altmann" <altmann at meteorite-martin.de>
To: <meteorite-list at meteoritecentral.com>
Sent: Thursday, July 22, 2010 6:00 AM
Subject: Re: [meteorite-list] Its official! NWA 6291 "The King
ofAngrites"for sale - AD


Huh, I found even a paper, which postulates, that the HEDs are from
Mercury
and the angrites from Venus....

http://www.lpi.usra.edu/meetings/otp2004/pdf/3012.pdf



;-)
Martin



-----Urspr?ngliche Nachricht-----
Von: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von
Jason
Utas
Gesendet: Donnerstag, 22. Juli 2010 11:27
An: Shawn Alan; Meteorite-list; Adam Hupe
Betreff: Re: [meteorite-list] Its official! NWA 6291 "The King of
Angrites"for sale - AD

Shawn,
Well-said -
But I can't emphasize enough the fact that such large bodies existed
in large numbers in the early solar system. That much is obvious from
the large numbers of ungrouped (and grouped) differentiated
achondrites that we have in our collections here on earth, as well as
from all various types of iron meteorites, which represent the cores
of diffeentiated planetismals. All in all, we have meteorites that
suggest well over 30-40 such bodies in the early solar system, and
computer-run models in some cases suggest hundreds of such bodies.

http://www.ucmp.berkeley.edu/education/events/cowen1d.html

http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System#For
mation_of_planets

Note that wikipedia suggests 50-100 such bodies. I wouldn't usually
reference wikipedia for something like this, but see references 35-36
for the article - that's actually a decent estimate that's been backed
up by some serious work done by experts -- it's not just a crap
wikipedia reference.

So, angrites may be from Mercury. If we say that, regardless of their
composition and history, they just needed to be from a large
planetismal capable of some metamorphic activity, then we've got a
1/50 to 1/100 chance that angrites are, in fact, from Mercury.

The trouble is that their chemistry and age suggest that they're not
from Mercury.

I agree. They *might* be from Mercury. And yes, some smart people
have said that they *might* be from Mercury.
But it seems to me that this article is being deemed credible because
of its authors, and not because of what it actually says.



>I do not refute Melinda Hutson's article that was never peer reviewed



>and


contains several errors according to the classifying scientists. I
asked
scientists about the article and they stated, it is obvious that she
didn't
read
the original peer reviewed abstract carefully, even mistaking the type
of
petrology that was discussed using formulas that simply do not apply to
the
texture NWA 2999 exhibits.

I'd like to know what these errors were, and how the error might have
affected her conclusions. Perhaps Adam or someone else would be
willing to explain her errors and how they suggest that angrites are
actually from Mercury.

Seems like this is the perfect sort of topic for the list...

Regards,
Jason




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