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[Guest_RGClark_*]

I posted the following to the space discussion list uplink.space.com. Now
Tempel I, Quaoar, and Enceladus all show signs of radiogenic heating.


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exoscientist
comet
01/14/06 04:52 PM
Re: Enceladus, the Europa of Saturn [re: telfrow][link to this post] Edit Reply


Some great posts in this thread.

Borman quoted this release:

NASA's Cassini images reveal spectacular evidence of an active moon
http://www.eurekalert.org/pub_releases/200...c-nci120605.php
"In some ways, Enceladus resembles a huge comet," said Dr. Torrence Johnson, imaging team member from NASA's Jet Propulsion Laboratory (JPL) in Pasadena. "Only, in the case of Enceladus, the energy source for the geyser-like activity is believed to be due to internal heating by perhaps radioactivity and tides rather than the sunlight which causes cometary jets."

However, the evidence from Deep Impact showing clays and carbonates suggest comets as well undergo radiogenic heating, which could possibly be as well the source of jets on the non-sunlit side of the comets:

Newsgroups: sci.astro, alt.sci.planetary, sci.physics, sci.geo.geology, sci.bio.misc
From: "Robert Clark" <rgregorycl>
Date: 8 Sep 2005 14:32:07 -0700
Subject: Carbonate and clay in comet Tempel I raise the possibility of life. http://groups.google.com/group/sci.astro/m...78647c737beb164

Some ref's for the theory of radiogenic heating in comets:

The Net Advance of Physics: ANNOTATED BIBLIOGRAPHIES, No. 1
Panspermia Theories: Annotated Bibliography, Section V
ORGANIC GRAINS, PREBIOTIC CHEMISTRY, AND LIFE ON COMETS.
http://web.mit.edu/afs/athena.mit.edu/user...ash/comets.html

Borman also cited the observation of higher temperatures and inferred radiogenic heating on the Kuiper belt object Quaoar due to the observation of crystalline ice:

Chilly Quaoar had a warmer past.
Crystalline ice suggests remote object has radioactive interior.
Mark Peplow
Published online: 8 December 2004.
http://www.nature.com/news/2004/041206/pf/041206-7_pf.html

This process is probably ongoing because of the limited lifetime of such ice on the surface. It has been argued that the radiogenic heating itself can not be continuing because the radionucleides causing it should have decayed away for small solar system bodies. However, the amount in such bodies is uncertain, based on detected amounts in some meteorites, whose parent bodies are uncertain.

Telfrow posted these great models for the radiogenic heating on Enceladus:

http://www.nasa.gov/mission_pages/cassini/...a/pia07725.html

and

http://www.nasa.gov/mission_pages/cassini/...a/pia07727.html

And provided this quote from New Scientist:

Giant water plume spews from Saturn’s moon
16:07 30 August 2005
NewScientist.com news service
Stephen Battersby
"Tidal friction
Internal heat must be driving all this activity, but the source of the heat remains a big puzzle. Natural radioactive decay in the moon's rocky core might warm the interior just enough to produce a sludgy plume of water and ammonia. This could heat the surface ice just enough to allow water to evaporate slowly.
"But Cassini also detected dust and whole ice grains in the plume, implying that the material is squirted out of Enceladus with some force. That would need a lot of heat – far too much to come from the core.
"An alternative is the tidal pull of Saturn's gravity, which makes the moon flex and produce heat by internal friction. But initial calculations put that at only 1% of the heat from the core."
http://www.newscientistspace.com/article.ns?id=dn7924

Note that if there could be sufficient radiogenic heat for Enceladus, to at least produce crystalline ice, it should also be sufficient for Quaoar which has more than twice the diameter, and would have more radiogenic material.

And in fact this is what all that may be required. Reikel in his post raised the possibility of exothermic reactions providing the necessary heating, though after an impact initiates the process.
However, Wilson et.al. have in fact proposed that radiogenic heating with accompanying chemical reactions could produce sufficient gas release to crack asteroidal/cometary bodies:

Early aqueous alteration, explosive disruption, and re-processing of asteroids.
Wilson, L.; Keil, K.; Browning, L. B.; Krot, A. N.; Bourcier, W.
Meteoritics & Planetary Science, vol. 34, no. 4, pp. 541-557 (1999).
http://adsabs.harvard.edu/cgi-bin/bib_quer...26PS...34..541W


Bob Clark

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