I posted the following to the space discussion list uplink.space.com.
Now comet Tempel I, Kuiper-belt object Quaoar, and Saturnian moon
Enceladus
all show signs of radiogenic heating.
Bob Clark
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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/2005-12/nsfc-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...@yahoo.com>
Date: 8 Sep 2005 14:32:07 -0700
Local: Thurs, Sep 8 2005 4:32 pm
Subject: Carbonate and clay in comet Tempel I raise the possibility of
life.
http://groups.google.com/group/sci.astro/msg/378647c737beb164
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/r/e/redingtn/www/netadv/bioast/clash/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/multimedia/pia07725.html
and
http://www.nasa.gov/mission_pages/cassini/multimedia/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_query?1999M%26PS...34..541W
Bob Clark
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