Hi,
Way too much stuff here to deal with all,
but I have a word about 2 Pallas as a
"Carbonaceous parent body."
Pallas has a silicate spectrum. A great many
bodies do. It shows signs of olive and pyroxene,
with low iron and water. If it resembles any
Carbonaceous chondrite, it's a CR with no
hydrated minerals or very little.
Pallas is very dark, with an albedo of 12%-14%,
almost as dark as our moon, whose albedo is
7% to 8%. Yes, when we look at the Moon
at night, it looks BRIGHT, but in reality, the
Moon is about the color and reflectivity of
a huge lump of black anthracite coal.
The fact that it doesn't look like a lump of coal
in pictures taken on the Moon or looked to the
astronauts as a very light grey demonstrates
the ability of the human mind to scale image
intensity to the Earth norm and to expose film
to achieve similar results.
Pallas is a little brighter than the Moon but
some darker than Mercury which is about 15%
to 16% albedo. Of course, if a human eye was ON
Mercury, the planet would appear to us as blazing
white under sunlight more than 2.5 times brighter
than here at Earth.
The density of Pallas is about 2.8. The similar
sized Vesta is 3.43, our Moon 3.35, Mercury . For
comparison, Earth's crustal rocks, mostly silicates,
have a mean density of about 3.0. It seems unlikely
that Pallas has an iron core. Like the Moon and
Mercury, it seems to be essentially waterless.
The spectral "classifications," both the Tholin and
the 2Mass, classify a great many asteroids as varieties
of "Carbonaceous," but we see far fewer Carbonaceous
meteorites than they see asteroids!
We spent many decades trying to analyze the surface
of the Moon spectroscopically, it being so conveniently
close and all, but none of it told us that much about
what we'd find when we got their. Similarly, spectral
studies of Mars from Earth are largely forgotten for
the same reason: they were wrong.
I expect Pallas to be excessively dry and waterless,
made of excessively dark rock, primitive in composition,
likely has little plagioclase on the surface, probably
isn't "differentiated" and lacks basalt melts. But hey!
I'm just guessing.
There is a chance that we may get a look at Pallas.
When the Dawn mission is mission is finished at Ceres,
if all systems are functioning and fuel supplies are
within parameters, it COULD be sent on a flyby of
Pallas. Dawn couldn't orbit it, but it could grab a lot
of lovely snapshots on that pass.
Of course, we'd have to get it funded by Congress...
Groan.
Sterling K. Webb
--------------------------------------------------------------------------
----- Original Message -----
From: "MEM" <[email protected]>
To: "Richard Montgomery" <[email protected]>; "metlist"
<[email protected]>
Sent: Wednesday, April 13, 2011 9:31 PM
Subject: Re: [meteorite-list] Cold Asteroids May Have A Soft
Heart(AllendeMeteorite)
Let me play politician and ask to "revise and extend my remarks".
There are
asteroid gurus on the list who are more likely able to address this
and I'd like
to hear from them. Your theory/question is partially in the right
direction so
let me re-frame it. I believe we have "likely" detected all the
existent
asteroids in our inner solar system which are large enough to have
formed
basalt/cores--aka differentiated. That size is hard
overlook(100-300km
minimum?). I read somewhere that as many as 12-20 major/minor planets
would
have formed in the early solar system that are no longer with us as
major/minor
intact bodies.( i.e. absorbed or ejected)
As to meteorite parent bodies, what we have yet to inventory and, for
which we
have not had a specimen drop by Earth for comparison, are these long
ago
disrupted bodies. These bodies which now are represented only by
minor,
irregular, slivers, slices, and rubble piles within certain swarms of
asteroids
in different sectors of the solar system.
There is a "diogenite-like" spectrum coming from an outer-belt
asteroid whose
orbit proves it cannot be related to Vesta. I mentioned the caveat
that there
may be some remnants of asteroids which were differentiated in the
early solar
system and for whatever reason are no longer in tact. We may only
have a
fraction of the original large body such that while we have located
all the
differentiated intact ergo larger asteroids, we may need to be
looking for
shards of former bodies to match meteorites from our collections.
The reason
all our "HED"s are from Vesta is probably that Vesta is on our "mail
route" and
quantum transport from Vesta to Earth is a favorable happenstance.
"1459 Magnya: Orbits in the outer main belt, too far from Vesta to be
genetically related. May be the remains of a different ancient
differentiated
body that was shattered long ago." Spectrum is diogenite-like
Another candidate which may be the source of olivine-diogenites but is
a chunk
off Vesta:
"2579 Spartacus — contains a significant portion of olivine, which may
indicate
origin deeper within Vesta than other V-types."
See list at:
<http://en.wikipedia.org/wiki/V-type_asteroid>
<http://en.wikipedia.org/wiki/4_Vesta>
Pallas and its family of asteroids is certainly a candidate for one of
the
Carbonaceous parent body, even thought it shows no major excavations.
"2 Pallas is a large and most certainly differentiated body but lacks
evidence
of a deep
excavation and its spectrum shows carbonaceous chondrite affinities.
However
75% of the astrtoids out there whose spectra we've measured fall in
the C or
Carbonaceous class."
<http://en.wikipedia.org/wiki/2_Pallas>
<http://en.wikipedia.org/wiki/Carbonaceous_chondrite>
Also in my reading there is good indication that the Martian moons are
captured
carbonaceous asteroids
<http://en.wikipedia.org/wiki/Moons_of_Mars>
Asteroid types More than I can retain in my head:
<http://nineplanets.org/asteroids.html>
<http://en.wikipedia.org/wiki/Asteroid_spectral_types>
* C-type, includes more than 75% of known asteroids: extremely
dark
(albedo 0.03); similar to carbonaceous chondrite meteorites;
approximately the same chemical composition as the Sun minus hydrogen,
helium
and other volatiles;
* S-type, 17%: relatively bright (albedo .10-.22); metallic
nickel-iron
mixed with iron- and magnesium-silicates;
* M-type, most of the rest: bright (albedo .10-.18); pure
nickel-iron.
* There are also a dozen or so other rare types.
Read more about Asteroids l Asteroid facts, pictures and information
by
nineplanets.org * C-type, includes more than 75% of known asteroids:
extremely dark (albedo 0.03); similar to carbonaceous chondrite
meteorites; approximately the same chemical composition as the
Sun minus
hydrogen, helium and other volatiles;
* S-type, 17%: relatively bright (albedo .10-.22); metallic
nickel-iron
mixed with iron- and magnesium-silicates;
* M-type, most of the rest: bright (albedo .10-.18); pure
nickel-iron.
* There are also a dozen or so other rare types.
Read more about Asteroids l Asteroid facts, pictures and information
by
nineplanets.org
Meteorites and their Parent Bodies 2nd Edition. Harry Mc Sween which I
think us
a google book online.
Elton
----- Original Message ----
From: Richard Montgomery <[email protected]>
To: Ron Baalke <[email protected]>; Meteorite Mailing List
<[email protected]>
Sent: Wed, April 13, 2011 8:39:46 PM
Subject: Re: [meteorite-list] Cold Asteroids May Have A Soft Heart
(AllendeMeteorite)
Ron and List,
This new evidence fits exactly into the recent question I posted,
'Vesta,
for sure?'
I only heard back from Elton (thanks, sincerely!) and yet now with
this
hypothesis, my question lingers as to the absolute recognition of
parent
bodies, with my query as to the yet-undiscovered potential pairings
of
undiscovered asteroids.
MEM pointed out that the largest asteroids (aka Vesta etal) have
already
been located, with tell-tale impact and reflective signatures that
rule out
other parents for our HEDs.
My new question, neophyte layman as I am, is:
Does this new data/theory bring my initial question about
Vesta-for-sure-as-parent-for-HEDs back into play?
-Richard Montgomery
______________________________________________
Visit the Archives at
http://www.meteoritecentral.com/mailing-list-archives.html
Meteorite-list mailing list
[email protected]
http://six.pairlist.net/mailman/listinfo/meteorite-list
______________________________________________
Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html
Meteorite-list mailing list
[email protected]
http://six.pairlist.net/mailman/listinfo/meteorite-list
