[meteorite-list] Slow cooling rate of irons in space

From: Jeff Kuyken <info_at_meteoritecentral.com>
Date: Sun, 6 Sep 2009 12:10:25 +1000
Message-ID: <0C802D459CFB49579EFFEC708A6D4467_at_JeffPC>

This is one of the best threads I've seen on the list for quite a while.
Interesting stuff!

So have the Martian Rovers found specific evidence from any changes that may
have taken place on Mars when it cooled? And what happens when the Earth
cools? Will this affect things like the Earth's electromagnetic field?

Cheers,

Jeff




----- Original Message -----
From: "Rob McCafferty" <rob_mccafferty at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Sunday, September 06, 2009 10:00 AM
Subject: Re: [meteorite-list] Slow cooling rate of irons in space


The "so darn cold" thing refers to objects not being lit/heated by their
star. Day sides will heat up until they radiate more heat than they absorb.
Night sides will cool as quickly as physics (and any atmosphere) allows.
If one face of Mars stayed pointing at the sun all the time, it would be
quite warm on a permanently daylit side. It attains 20degC at the equator
during the day as it is.

Given that the only method of heat transfer is conduction, requiring direct
contact of atoms, until you get to the surface where they can radiate heat
away, it seems more reasonable that a moderately sized body may keep a hot
core warm for a very long period of time. Particularly if you have the core
covered with a crust made of poorly adjoined fragements of rock, acting as a
blanket possibly hundreds of km deep.

The physics of the planetary cooling has long been worked out. For me, the
amazing thing is just how the mass of the planet changes the cooling time.
Mars is believed to have stayed hot enough to keep it's volcanoes going
until 1Ga ago. Now it's interior is too cold.
Smaller bodies generally stopped being active much earlier. Venus they're
not sure about.

Rob Mc
Rob McC


--- On Sun, 9/6/09, Pete Shugar <pshugar at clearwire.net> wrote:

> From: Pete Shugar <pshugar at clearwire.net>
> Subject: Re: [meteorite-list] Slow cooling rate of irons in space
> To: "Carl 's" <carloselguapo1 at hotmail.com>,
> meteorite-list at meteoritecentral.com
> Date: Sunday, September 6, 2009, 12:34 AM
> May I please inject just the one
> comment?
> In space, the side facing the star (in our case, the sun)
> can get quite hot, ie close to the sun --hotter, and further
> away---less hot.
> Conversly--the side away from the star can approach very
> high negative degrees, ie 250 to 400 below zero.
> This is the "so darn cold" you were thinking about.
> Pete
>
> ----- Original Message ----- From: "Carl 's" <carloselguapo1 at hotmail.com>
> To: <meteorite-list at meteoritecentral.com>
> Sent: Friday, September 04, 2009 8:18 PM
> Subject: [meteorite-list] Slow cooling rate of irons in
> space
>
>
>
>
> Hi Elton and All,
>
> I've read about the very slow cooling rate of the molten
> iron in various books but I don't understand why this is so.
> Why would it take millions of years for just a few drops of
> degrees? It's hard for me to envision this even accounting
> for bombardments and radioactive decay. Radioactivity from
> the original super nova event, right? Maybe it's
> because I think of space as being so darned cold it wouldn't
> take anything long to lose heat and freeze up. I realize
> radioactivity takes a long time to decay but would it take a
> lot or so little to keep a large planetary body hot for so
> long? Thanks.
>
> Carl
>
>
>
> Eman wrote:
> > I think this theory has a potential fatal flaw if what
> we think we know about
> taenite/kamacite growth is valid. Without an insulating
> blanket the molten
> pool will not exist in a molten state long enough to permit
> crystallization aka
> Widmanstatten patterns.
>
> Be it remembered that Widmanstatten pattern/crystal growth
> is very very slow on
> the order of 10's of degrees cooling per million years. It
> is difficult to
> develop a scenario that integrates a large crater on an
> Goldilocks Asteroid
> which works.. ..
>
>
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Received on Sat 05 Sep 2009 10:10:25 PM PDT