[meteorite-list] Dwarf Planet 'Becoming A Comet' (2003 EL61)

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Sat, 3 Feb 2007 14:25:04 -0800 (PST)
Message-ID: <986923.78649.qm_at_web50910.mail.yahoo.com>

Apologies for taking selected bits. Hope it's not out
of context.

--- "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
wrote:

''2003 EL61 is a very bright body, reflecting 70% of
the
light that falls on it, and it is indeed, as you would
suspect
from this brightness, covered with water ice. BUT,
it's not
old water ice, but new, freshly fallen crystalline
ice,
otherwise known on our planet as snow''

Curiously, Halley's comet has an abledo of less than
4%, less than that of coal or black velvet. While
Halley is not necessarily typical of comets, it is
agreed that comets are very dark objects.
Nucleus[nuclei] sizes have been estimated by removing
modelled coma brightnesses from Hubble images and for
nearby comets radar measurements seem to confirm the
low albedo.

Cometary dust may begin as silicate grained materials
mantled with organic matter. To this hundreds of
0.01micron ice particles may form from a protosolar
nebula into .5micron grains. These cluster into loose
agglomerates which end up being part of the coma of
comets. The evidence for this theory is the particles
swept up by high altitude research planes [18km up]
believed to be cometary in nature. This being the case
it explains the brightness of the coma and -might I
suggest- the brightness of EL61. It need not be
covered in ice, just covered in this cometary 'snow'


''Now, we come to the Giant Comet Notion. Obviously,
2003 EL61's ice is a surface feature, a thin layer of
volatiles
over what is essentially a rocky body.''

Comets are generally considered to be a thin layer of
rocky material over a lot of volatites, the complete
opposite. I could well be wrong on this. Virgin comets
are unusually bright on their first perihelion
passage. One theory is that the surface volatiles ar
vapourised away leaving this outer layer of dark
material. This would suggest that if EL61 is indeed,
becoming a comet, this is it's first journey inward
which seems most unlikely. Also, comets sublimating
ices have a temperature of 230K. Virgin comets can
achieve this much farther out than comets on
subsequent passes. This is because the dark silicate
layer protects the icy material, insulating it. Only
when the comet gets much closer does the heat conduct
in to cause the sublimation of the ices. However, I
doubt anyone would suggest EL61 has a surface
temperature of >200K. There has to be an alternative
explanation.


Sorry the reply so lengthy. I just don't think EL61
can be cometary in nature.

One other think caught my attention in this post

   '' A mere 10% decrease would lower the planetary
temperature
by 7 degrees C''

I thought the difference between aphelion and
perihelion in earth's orbit made a 7% difference in
solar intensity. Does anyone have a guess as to how
long a change need apply for to effect earth? I
suspect not

Rob McC





 
____________________________________________________________________________________
Expecting? Get great news right away with email Auto-Check.
Try the Yahoo! Mail Beta.
http://advision.webevents.yahoo.com/mailbeta/newmail_tools.html
Received on Sat 03 Feb 2007 05:25:04 PM PST