Sent this through earlier but it never appeared on List.
Think it was too long; too many replies to replies to
replies. Shorter now. If a duplicate, sorry 'bout that...
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Hi, Doug, List,
why Jupiter is so Special...
The earliest scientific model for "How To Make
A Solar System" is condensation from a hot solar
nebula. Too simple to be the whole story, it's still
a kind of framework to hang the details on...
The point where water will condense from a
vapor directly into a solid in the low pressures of the
nebula is called the "Snow Line." Since water is
made from the most common element and the third
most common element (and the second most
common element is too noble to get involved in
this sordid affair), there's going to be a lot of it
once it decides to turn solid.
Any little lump that happens to be humming along
right at the orbit where the Snow Line forms is going
to suddenly start growing fatter faster than any other
little lumps, and --- well, the process just snowballs!
Jupiter is an anomaly...
At a certain mass, another "snowballing" effect
takes place, when the mass of the lump is great enough
(estimated to be ~10 Earth masses) to hang onto a
lot of the H-He gas that's everywhere. And before
you know it, you got a Jupiter!
Jupiters are greedy; we think the only thing that
stops them from gobbling up all the gas is that the
newborn solar system runs out of gas! So, Super
Jupiters just formed in a more gas-rich nebula or
one where the gas persisted longer.
While our look at 200 extra-solar planets is very
biased --- the easiest to find are close super-Jupiters,
so we find lots --- we do find big Jupiters, small Jupiters,
even Saturns and Super-Earths. We conclude that's
what they are strictly by the one parameter, though ---
mass and nothing else. Wouldn't it be odd if some
of the close-in heavyweights turned out to be, not
gas giants, but Rock Giants?!
Take one dust-rich, gas-poor nebula where a
stellar hiccup blows off the gas near the star early in
the accretion process, and a run-away terrestrial
world develops, not 10 Earth-masses, but 100 or
200! (Jupiter=318)
Jupiters appear to be common, if not vulgar.
that something in the dynamical formation favors
pairs, i.e., twins of planets in a stable configuration.
So you get the Venus/Earth pair, then the Jupiter/Saturn
pair, and finally the Uranus/Neptune pair. Venus is
81% Earth's mass, Jupiter is 330% Saturn's mass,
Uranus is 82% Neptune's mass
I'm not quite ready for a ride in the twin-mobile of
Solar System Theory, but oddly I think your later
remark (below) is a Grade A brainstorm:
That leaves Mars an asteroid as much as Ceres.
I imagined looking at the first good image of Ceres
sent back by the Dawn Mission, and --- Mini-Mars! Of
course, this could easily be dead wrong. Mars is almost
twice as dense as Ceres, but I saw a lot of similarities.
Ceres and Mars both have lots of clays on the surface;
both have probably cooled internally producing crust
crack canyons; both have a lot of volatiles incorporated;
their temperature ranges are not that different (~40 C).
Maybe I should say "could have," or "might have."
You made me look at Ceres a new way. And that
will have to do until the year 2015...
Of course, planets are like people: individual.
Jupiter and Saturn are not really very much alike;
neither are Uranus and Neptune. I think Neptune is
a very gassy Super-Terrestrial, a hybrid. Ceres may
look like nothing else we've seen; that is, it may look
exactly like... itself.
the Venus/Earth pair
We really are alike, up to a point, so much so that
we attribute the nasty differences to the way the planets
have evolved. We cling to the similarity in that way. You
referred to "narrow zones" of accretion; well, Earth and
Venus are accorded the narrowest zones which are then
jammed up close together, a point often missed: no two
planets in the solar system are as physically close, i.e.,
in proximity, as the Earth and Venus. Maybe they're
fraternal twins... Some have called Venus the Earth's
"Evil Twin"!
I note with interest that Grinspoon, the most loyal
Venus expert, who started out with a Venus that was
bad from birth, has moved toward a view that calls
for a wet temperate Venus for most of its history,
until it finally went dry a billion, or 600 million, years
ago. New computer modeling. That's what happens
as you fall in love with your object of study...
Personally, I favor the notion of a really nice, stable
Earth-like Venus up to 400-600 million years ago when
a series of devastating impacts more severe than the
Late Bombardment melted the crust down to the mantle,
devolved all the oceanic carbonates into CO2, etc. (If
you did that to the Earth, you'd get a 96 bar CO2
atmosphere; Venus has a 90 bar CO2 atmosphere;
neat fit).
Oddly, enough, I can make this model fit all the
oddities (argon abundances, crater counts, etc.) that
can't be explained, and find evidence of this event
elsewhere in the solar system. Someday, I will publish
a crank book with a garish cover about it...
"Venus Didn't Die --- It Was Murdered."
No math from me this time since I think these are stochastic collision
processes and not definite closed form solutions, so they need completely
different statistic mechanics type approach.
I agree with you on this one. At least, I hope so.
What would be the point of traveling to the stars
only to find a thousand minor variations on our own
set of worlds? Back when I used to play with dynamic
simulators, I used to try to create stable solar systems
with as many "habitable" worlds as I could fit in. One
of the keys to doing that is keeping your gas giants
small and/or far out in the system.
Getting three nice terrestrials is easy if you control
their masses; you get a warm one, a temperate one,
and a cold one. Tinkering will get you four, but one
is usually pretty cold or pretty hot. The sneaky thing
is to put a warm sub-Uranian in that's close enough
to have habitable satellites without perturbing its
smaller neighbors. I got up to seven habitable worlds
that way, and it was stable (at least for a half billion
years).
Then, there's the solar system with only one big
gas giant and whose inner system is just an extended
asteroid zone with lots of sub-Terrestrials crammed
in without de-stabilizing each other, just as our asteroid
zone has its "big" members co-existing. That way you
can get 12-20 habitable worlds, if you like'em small
(nothing bigger than Mars and maybe none as big),
thin-aired, and good for jumping high...
And we haven't even talked about places where
other forms of life could exist:
"Nitrogen- or methane-breathers in liquid methane is
a distinct possibility, in our Solar System, on Titan.
There can be found methane in all three phases (solid,
liquid, and gaseous); water ice on that frigid world
is a hard rock suitable for geological or architectural
construction! Because methane is a non-polar fluid,
proteins are out for the core chemistry: instead life
would be constructed of complex fats (possibly
using protein-based cell walls!) probably incorporating
nitrogen reactions. The biochemistry might consist of
nitroproteins -- explosive at Earth temperatures, but
just active enough to react at a steady rate in the cold
conditions of their native environment."
Variation seems to be The Plan. There is a story
that when Darwin was old, he visited by a delegation
of clergy who had more or less come to grips with
evolution, but they wanted to know if, in all Darwin's
long experience of Nature, he had learned anything
from Nature about God's Nature. The elderly Darwin
thought for several moments and then replied, "Well,
He does seem to be AWFULLY fond of beetles..."
(The story is deduced to have come from J. B. S.
Haldane in his old age, and is often quoted as
"inordinate fondness for beetles.")
He was referring to the fact that there over 540,000
species of beetles when obviously all their functions
could be performed by, at most, only 30-50 species,
or so it seems to us, but then perhaps we don't like
beetles as much as God does.
I bet He likes planets, too.
Sterling K. Webb
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----- Original Message -----
From: "MexicoDoug" <[EMAIL PROTECTED]>
To: "Meteorite List" <[email protected]>
Sent: Wednesday, September 20, 2006 6:57 AM
Subject: Re: [meteorite-list] 2003 EL61, IN PERSON
Alternate title of this post for the interested:
How 2 Molecules Initiated the Solar System, Simple Assumptions behind the
Accretion Disk by a "Layman", The Folly of the "Orbit Clearing" Criterion,
and IAU Disconnect from the Genesis Starting with the Pre-Solar Nebula
(opinion), and why Jupiter is so Special by Random Occurrence
Hello Sterling,
Glad to see you back on the planet debate and not being Brown's deputy
cyber
sleuth!
This time I really enjoyed your comments, and agree heartily with you and
your critical comment summing up the damaging attitude in some astronomy
circles & quoting you:
'"NOW, we know it all." It's only been 14 years since we found the first
"TNO." Again, largely due to a substantial improvement in the technology.
We
are just now having our eyes opened wider, again. I don't the process is
over. I think it's just starting.'
No math from me this time since I think these are stochastic collision
processes and not definite closed form solutions, so they need completely
different statistic mechanics type approach.
Let me add my "spin" on your post, from a layman's point of view who is
too
lazy to study what's really beyond this. You commented: "IAU dump Mercury
from the Honor Roll of Planets and assign it to Brian Marsden's care, if
that happens...The Nine, no, Eight, no, SEVEN planets of The Solar
System!"
I'd naively say if we must take this route it might be worthwhile
considering SIX planets after dumping Mercury and Mars. It is pretty
clear
to me from a clean dynamical view that it be want to get prissy on the
planets, that something in the dynamical formation favors pairs, i.e.,
twins
of planets in a stable configuration. So you get the Venus/Earth pair,
then
the Jupiter/Saturn pair, and finally the Uranus/Neptune pair.
Venus is 81% Earth's mass
Jupiter is 330% Saturn's mass
Uranus is 82% Neptune's mass
I won't talk further about the "pairs" as I am not sure I can back it with
standard science. Continuing, the inner planet should be smaller since it
has less of a ring to clear out. That fails with Jupiter.
Jupiter is an anomaly, but in statistical problems this is not really at
issue since it just happened in a continuum of possibilities. Mars and
all
the asteroids in the main belt, and possibly including Terra's original
Moon
impactor probably would have been another planetary pair, between Earth
and
Jupiter, that principally all got eaten by Jupiter because of a few chance
occurrences a few billion years ago that just as well could have left a
planet in the asteroid belt - a classic science fiction type scenario that
you go in a time machine and toss one small meteoroid out 4.4 billion
years
ago and the Solar System, like a universe of dominos falls out in a
different way. Really - this could lead up to one chance collision in
that
zone that sent more material to Jupiter. I think logic works here a
little:
If everything formed out of the presolar nebula - why the Dickens is
Jupiter
so big? It was all a relatively uniform nebula supposedly and then
something happened to make Jupiter snowball. No preconceptions allowed!
Probably a simple accident and no fancy proto-photosphere radius crazy
explanation. That leaves Mars an asteroid as much as Ceres. If this is
hard to believe, just look at Sterling's logic of "clearing orbits" which
is
currently in vogue. Mar's got a much bigger hunk than earth yet is a
shrimpy size. Totally out of wack! All that material in that little
space
around the Sun that purportedly made Venus and Earth, and then you need to
go all the way to Jupiter to find anything of significant mass? As a
layman
on this issue, here's where I think the current folks in IAU voting for
the
"forever and ever solution" Jay Pasachoff so melancholically stated have
fallen flat on their faces. Grinding out big models and complex
mathematics
doesn't even serve up doo-doo if you don't start from first principles -
and
I think this is part of what is lacking in the current planet problem and
at
the heart of the annoyance of the whole thing.
So truly, Mars and Ceres are the best candidates to be dwarf planets based
on a simple density argument. Mars should be, for argument sake 82% the
size of Ceres and they should both be quite a lot larger than Earth from a
Aristotelian harmony in prediction.
The fact that Ceres was named a dwarf planet, but Mars not, can only mean
to
me that a bright Mars in Earth's sky makes it a planet. If Ceres were
twice
the size (but smaller than Pluto), it would be a Planet no matter how much
rubble circulated with it. How could one possibly say no, with Jupiter in
its shadow, a monster by random processes, calling the gravitational
shots?
So we get to Pluto. Too small, in orbital resonance, too inclined, not
clearing it's zone (BS), too cold, too far, whatever chance variable you
like. Really we need to again go back to first principals for the layman.
It's round, its accreted, its in a stable orbit, and it probably has some
sort of differentiation - but no one really knows exactly what (We will
check that with New Horizons, though, so what's the haste, oh, right Mike
Brown et al need to name their objects so screw it Pluto's not a planet,
now
we don't have to deal with the nature of the Solar System before we
recognize the new discoveries).
Let's go back to the formation of the Solar System from it's postulated
pre-solar nebula. First, review what happened according to popular belief
backed up from direct observations of other stellar nurseries around the
galaxy. There was a dark cloud of matter. Something disturbed it and
drops
coalesced like rain...in space...and gravitational attraction made sure a
gravitational storm was to come. Wherever this seeding first occurred in
the nebula, that tiny imperfection, those two molecules that first stuck
together - they determined the center of the Sun and everything we
know...that's where gravitational condensation first took off.
A huge gaseous proto-Sun was formed that was less dense than the lightest
super giant. Slowly at first it formed a nicely gravitational spherical
bubble, first enlarging until it reached the threshold to recede faster
than it grew. That's natural, as mass would grow as a cube,
but...attraction only as a square. The compression began. As more and
more
coalesced, the gravity became stronger and stronger, and matter from the
center to Neptune or thereabout heated up greatly and started spinning as
it
contracted. Then we are to believe with probability, the spinning got
faster and faster as it shrunk more and more. Suddenly the pressure was
so
great and the radiating energy not enough that nuclear fusion 'ignited' as
things got so dizzying that this spin oddly created a plane and perhaps
spit
material out of the system through the spin axis. The centrifugal force
of
spin so great that some mass stayed along the equatorial arc and that
formed
what we call the accretion disk.
Just a few questions I can think barely a drop in the bucket for a
beginning...the less altered material in the outer reaches is spinning and
revolving as a result, is condensed, of course not as heated, and not
having
as much orbital energy from this centrifugal event as distance increases.
Was it spinning with the core of the Sun? Yes most probably. Being
further
out it was a little cooler. But the fact that it is somewhat disk or
doughnut shaped goes a long way in proving that it was part of the
dizzying
formation. Some things out of plane? Fine! What's the big deal? Why
does
a planet have to have been brought in line? Why does the definition need
to
be re-written - planets can only be produced by the Sun's waistline? Why
do
we want to insist on that? How do we know they weren't in plane before,
anyway? With such weaker attractions to the Sun the interbody
interactions
are greater out there. Collisions occurred, accretion occurred. How else
could such big "planets" be found out there. It was real and it happened.
Remember Mars now. Mars didn't clean out its orbit by itself. Jupiter
took
most of it. Just as it took most from "Ceres", and play havoc in that
neighborhood.
In spite of all that, Mars formed and it's there. Ceres formed and its
there. They are round and they go around the Sun within a tolerance,
even.
Pluto is no different. The oddball in the Solar system isn't Pluto, it's
not Mars, not Earth, it's Jupiter who chance snowballed to a 7 AU radial
sucking ability. An alien coming from afar would pick up on this right
away. The rest are a bunch of Christmas ornaments decorating Jupiter as
it
goes around the Sun. Including Pluto, and Eris (we are told is nicely
round). What kind of argument could possibly discriminate against Pluto,
Mercury, Mars...oh I see...someone has decided that round things going
round
the Sun are no big deal. To be a "Planet" you need to have experienced
reached X's arbitrary centrifugal force...the Solar System bodies that
didn't are a different race of rocks. A discriminated race by the IAU
because the revolve far away and they are darker worlds. Yeah - they
associate with comets, is the common wisdom. Haven't we found enough
NEO's
to realize how foolish this discrimination by association is? Because in
some Artist's conception they weren't illuminated as white hot as the
dinner
plate model of the accretion disk...How pathetic of an interpretation...at
best a theoretical rewriting unnecessary, redefinition reprocessing
revisionist idea on what a planet is.
Gravity-Rounded and revolving. Asteroid? No, that's a fragment of
something bigger. Planets have 100% crust, which can be an atmosphere to
include the gas giants in the category, until someone goes and touches
down
on the solid parts..
Best wishes, Doug
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