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

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Wed, 21 Feb 2007 15:28:26 -0800 (PST)
Message-ID: <283457.31126.qm_at_web50911.mail.yahoo.com>

In the context of what I had written I concede this is
a fair point.
However. I'd like to know which comets have confirmed
hydrovulcanism and where the info source.
I can appreciate it happens but the energy source for
such an event seems lacking once beyond the ice line.
I am quite willing to blame my own shortsightedness
for this.

It's just I don't think this thing is coming or has
ever has come into the inner solar system before. It
just doesn't match the pattern my half arsed look has
seen.

Rob McC



--- Jason Utas <meteoritekid at gmail.com> wrote:

> Hello Rob, All,
>
> >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.
>
> And yet, this would all depend on the amount of
> hydrovolcanism on the
> surface of the body itself - if there were enough
> activity to completely
> resurface the2003 EL61 with ice since it experienced
> it's great impact,
> what's to say it hasn't been resurfaced since its
> last close perihelion?
> I know that some comets have geysers of their
> own...is there any data around
> that tells us how long it might take for any
> particular comet (I know many
> would be different) to completely resurface itself
> with ice and thus enter
> the inner solar system brighter than when it had
> last left?
> Regards,
> Jason
>
>
> On 2/3/07, Rob McCafferty <rob_mccafferty at yahoo.com>
> wrote:
> >
> > 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
> >
> >
> >
> >
> >
> >
> >
> >
>
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Received on Wed 21 Feb 2007 06:28:26 PM PST