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

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Mon, 19 Feb 2007 18:22:45 -0800
Message-ID: <93aaac890702191822i4cd9b099i386b897cda5221d6_at_mail.gmail.com>

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 Mon 19 Feb 2007 09:22:45 PM PST