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

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Sat, 5 Sep 2009 17:00:59 -0700 (PDT)
Message-ID: <360005.92513.qm_at_web55201.mail.re4.yahoo.com>

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 08:00:59 PM PDT