[meteorite-list] Study: Earthlike planets may be common

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sun Sep 10 06:12:20 2006
Message-ID: <005e01c6d4c1$926f4460$5227e146_at_ATARIENGINE>

Hi, Darren, List.

    Original press release from U. Colorado:
http://www.colorado.edu/news/releases/2006/280.html
has more detail than the Reuters story and actually
explains the mechanisms and how they reached the
conclusions they did, which the Reuters story does not.

    If the Reuters story sounded a little whacky, read
the above instead. These are long computer simulations:
15 runs of 8 months of number crunching, inventively run
on 15 big PC's. (Cheaper than a Cray, I guess, but is
15 enough?)

    To start with, our solar system contained Mercury, Venus,
Earth, Mars, Artemis, Jupiter, Saturn, Neptune, and Uranus
(in that order!), did a little dance, planets move in, planets
move out, planets get kicked out of the system; it's lively.

    The abstract of the actual scientific paper is at:
http://www.sciencemag.org/cgi/content/short/313/5792/1413
but you can't read the full article without the $99/year
subscription...

    Sean Raymond is also the proposer of the notion of the
Mars-sized Artemis, the fifth planet, which orbited at the
inner edge of the present Asteroid Zone, at 2.0 AU, for
700 million years (4.5 bya to 3.8 bya):
http://catdynamics.blogspot.com/2006_03_01_catdynamics_archive.html

    This is pretty much the same idea put forward by Chambers
(only with a smaller, half-Mars planet) a few years ago, called
the Planet V hypothesis:
http://www.space.com/scienceastronomy/solarsystem/fifth_planet_020318.html
and
http://www.aas.org/publications/baas/v33n3/dps2001/505.htm
about which we had a thread back in April.

    As far as the notion that most "Earth's" in the galaxy
would be far wetter than our Earth, that the majority would
be "waterworlds," the credit for that idea goes back to
1982 and physicist/science fiction writer David Brin. He
used it as a suggestion as to why SETI searches have
turned up no Earth-like neighbors, which I discussed
before on the List:
http://six.pairlist.net/pipermail/meteorite-list/2006-February/181270.html

> The terrestrial planets should have (so the argument goes) so
> much more water than the Earth that they are all Waterworlds.
> Intelligent life evolves, yes, but underwater, so the smart aliens
> are all brainy dolphins and cephalopods, very philosophical,
> but with no hands, no technology, hence no radio (David Brin).

    Of course, there has been a recent flap over a neurologist
who has published an analysis that whales and dolphins are dumb:
http://www.msnbc.msn.com/id/14388922/
I can't find his original publication because Google is clogged
with hundreds of outraged posts screaming that he is the DUMB
organism. Saying something derogatory about dolphins is a sure
way to upset people.

    I have previously registered dismay at "dynamicists" deciding
what a planet is, yet every time one of them does a new computer
simulation of the solar system, the whole origin of the system is
redefined, which will inevitably cause the dynamicists to fracture
into more sub-schools with every contradictory simulation, until
there are as many schools of thought as there are thinkers...

    What ever happened to evidence? Is speculation less speculative
if a computer does it? I happen to agree with the trend emerging from
the last five years of simulation, so maybe I shouldn't complain. The
trend I refer to is the idea that the present number and configuration
of planets was not set in stone 4.5 billion years and remained
unchanged ever after, but that the solar system has evolved and
changed over the aeons, that its present state is just that: the way
it is right now, just a phase, or perhaps an end state.

     The last time anyone tried to "regress" the solar system, that is,
run it backwards to see what happened, it was only completely
stable for about 400 to 600 million years "backwards." And by
800 million years backwards, it was a MESS, completely whacky
and coming apart. This was done using a dedicated hardware multi-
processor computer with more than "super-computer" capacity
for this kind of calculation than a super-computer would have had.

    ["A Digital Orrery,'' James Applegate, M. Douglas, Y. Gursel,
P Hunter, C. Seitz, Gerald Jay Sussman, in IEEE Transactions on
Computers, C-34, No. 9, pp. 822-831, September 1985, reprinted
in Lecture Notes in Physics #267 -- Use of supercomputers in stellar
dynamics, Springer Verlag, 1986]

    So, all we know for certain is that the solar system has been
configured in the present arrangement for, say, 600 million years,
but before that we either a) don't know, or b) it was different. There's
a big gap between 3800 million years ago and 800 million years ago;
a lot can happen in three billion years! But while many can accept
a messy solar system back in the good old days of 4 Billion BC,
they get very uncomfortable about a really messy solar system that's
much closer in time, a kind of cosmic Not In My Back Yard feeling.

    The evidence for unsettled times in the solar system is there
in the CRE ages of iron meteorites. Cosmic Ray Exposure (CRE)
dates tell us how long chunks of core have floated around as the
small fragments we find now. If collisions are uniform and random
we would find CRE ages spread out, but instead there are sharp
peaks around which CRE ages cluster, at 1000, 650, and 400 million
years ago. At those dates, there were BIG episodes of collisions
and breakups, flurries of big impacts. And if you're smashing the
iron cores of planetesimals and large asteroids, you have to use
a still BIGGER hammer to do it with.

    Interestingly, there are very few irons with CRE ages in the last
100 million years, so, yeah, things have been pretty calm lately.



Sterling K. Webb
-------------------------------------------------------------------------------
----- Original Message -----
From: "Darren Garrison" <cynapse_at_charter.net>
To: <meteorite-list_at_meteoritecentral.com>
Sent: Friday, September 08, 2006 10:54 AM
Subject: [meteorite-list] Study: Earthlike planets may be common


http://www.cnn.com/2006/TECH/space/09/08/earthlike.planets.reut/index.html

WASHINGTON (Reuters) -- Earthlike planets covered with deep oceans that
could
harbor life may be found in as many as a third of solar systems discovered
outside of our own, U.S. researchers said on Thursday.

These solar systems feature gas giants known as "Hot Jupiters," which orbit
extremely close to their parent stars -- even closer than Mercury to our
sun,
University of Colorado researcher Sean Raymond said.

The close-orbiting gassy planets may help encourage the formations of
smaller,
rocky, Earthlike planets, they reported in the journal Science.

"We now think there is a new class of ocean-covered, and possibly habitable,
planets in solar systems unlike our own," Raymond said in a statement.

The team from Colorado, Penn State University and NASA's Goddard Space
Flight
Center Maryland ran computer simulations of various types of solar systems
forming.

The gas giants may help rocky planets form close to the suns, and may help
pull
in icy bodies that deliver water to the young planets, they found.

"These gas giants cause quite a ruckus," Raymond said.

Water is key to life as humans define it.

"I think there are definitely habitable planets out there," Raymond said.
"But
any life on these planets could be very different from ours. There are a lot
of
evolutionary steps in between the formation of such planets in other systems
and
the presence of life forms looking back at us."

As many as 40 percent of the 200 or so known planets around other stars are
Hot
Jupiters, the researchers said.
Received on Sun 10 Sep 2006 06:12:07 AM PDT