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 <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]> > wrote: > > > > Apologies for taking selected bits. Hope it's not > out > > of context. > > > > --- "Sterling K. Webb" > <[EMAIL PROTECTED]> > > 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! 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