[meteorite-list] Comet smashes triggered ancient famine ???

From: ensoramanda at ntlworld.com <ensoramanda_at_meteoritecentral.com>
Date: Sun, 11 Jan 2009 19:35:21 +0000
Message-ID: <20090111193521.E6CFR.451661.root_at_web03-winn.ispmail.private.ntl.com>

Hi Larry, Rob,

Thanks for all that info and sorry for my dumb reply in haste last. I was not thinking of SL9 at all but a completely different object mentioned in the lecture. I wish my memory was better.

Graham Ensor UK

---- lebofsky at lpl.arizona.edu wrote:
> Hi Graham and Rob:
>
> Some of this is from memory and some of this I had to look up. David Levy
> was actually working part time for me at the time doing education
> outreach, so I know some of the details.
>
> 1. As far as I know, scientists still do not know where SL9 came from
> ("beyond Neptune"). Probably a captured comet that happened to come too
> close to Jupiter on its first pass or one of its first passes into the
> inner part of the Solar System.
>
> 2. At some point in time (1960s to 1970s), the comet(?) soon to be called
> SL9 was captured in a 2-year orbit around Jupiter. Good for it, a new moon
> of Jupiter!
>
> 3. However in July of 1992, SL9 passed within 30,000 to 40,000 km of
> Jupiter's cloud tops (Jupiter radius is about 71,500 km). This is within
> the Roche limit of Jupiter (gravity-induced tides from Jupiter stronger
> than the strength of the material that makes up the body; a little more
> complicated than that, but good enough for this).
>
> 4. Observed first seen by Carolyn Shoemaker (observers Gene and Carolyn
> Shoemaker and David Levy; interesting story). Then confirmed by Jim Scotty
> here in Arizona (the first famous image of the string of pearls).
>
> 5. Soon determined to be in orbit around Jupiter (though only "seen" once
> prior to that but not noticed by the person who took the image). A highly
> elliptical orbit that had it going as far as 50,000,000 km from Jupiter
> (but still in orbit). Repeating myself, a 2-year orbit, probably in orbit
> for 20 or 30 years.
>
> 6. Soon to be determined that its orbit was continually changing slightly
> (gravity of the Sun and mass loss of the comet which alters the orbit
> slightly). The result was that in Juuly of 2004, it would be at its
> closest to Jupiter again, but this time, its closest distance to Jupiter
> would be 45,000 from the center of Jupiter, 26,500 BELOW the cloud tops of
> Jupiter!
>
> 7. So, the reason that all of the pieces hit Jupiter was that they were
> all in the same orbit, just strung out in space (and time along an orbit
> that got the pieces way too close to Jupiter).
>
> 8. I think that the best estimates (not all agree) are that the largest
> pieces were at most 1-2 km in diameter with most pieces less that 1 km in
> diameter. This makes this event a once in a thousand-year event (give or
> take).
>
> 9. This helps explain crater chains on two of Jupiter's satellites: Europa
> and Ganymede (16 total?). A comet gets too close to Jupiter, breaks up and
> you get a string of comets that, on their way away from Jupiter run into
> one of the satellites, leaving a crater chain. Too close together and
> there would not be a chain. Too far apart and only one or two would hit
> the satellite and the others would miss.
>
> To get crater chains on Earth, you would have to have a comet or asteroid
> break up before hitting the Earth, either by a close approach to Earth
> (unlikely) of the Sun. However, it is unlikely that this object would get
> captured by the Earth (they are moving fast and Earth not that massive).
>
> A breakup as the object was approaching the Earth (say in the atmosphere)
> would not give the pieces time enough to spread out and make multiple
> craters (the long discussion on double craters on Earth). So the pieces,
> as I said before, would have to be close enough together in order for the
> individual pieces to hit the moving Earth target and really close to make
> a chain on Earth. The Earth is moving at 30 km/s and a comet is moving at
> probably 40 or 45 km/s. So, you can easily figure out how close the pieces
> have to be.
>
> A bunch of impacts over a few thousand years is another story that is
> beyond the above discussion.
>
> Larry
>
>
>
>
>
>
> On Sun, January 11, 2009 2:49 am, ensoramanda at ntlworld.com wrote:
> > Hi Rob,
> >
> >
> > Went to a lecture at our astronomy society about Jupiter and it acting to
> > capture or perturb objects (friend or foe etc) the other night.... and I
> > believe it was said that SL9 only made two passes before it met jupiter
> > again on jupiters next turn around the sun and was thus flung out never
> > to be seen again. eg Jupiter was on the opposite side of the sun on SL9's
> > first time round with no effect and thus was very close 2nd time round
> > and able to change its orbit again.
> >
> > I hope I remembered that right!
> >
> >
> > Graham Ensor, UK
> >
> >
> >
> > ---- Rob McCafferty <rob_mccafferty at yahoo.com> wrote:
> >
> >> Fair point, but it may well be a poor choice of words on my point.
> >>
> >
> > The "Swarms"/"showers" you mention are what are suggested in the book.
> > Several objects arriving in quick sucession are not unusual, however.
> > There is evidene of it happening on most solid bodies. They all have
> > strings of impact craters where many objects obviously arrived in a
> > matter of hours producing chains of craters. My problem with this is that
> > the authour is perhaps suggesting several over the last few millenia. If
> > the "chain" events were that prevalant, one would expect them to dominate
> > on solid bodies and they don't.
> >
> > Your points are well made. I was not aware that SL9 was in orbit of
> > Jupiter. The implications of this are complex and I'll need to check how
> > long for. I Doubt it was for long but even so, how this is related to
> > comets and the earth is beyond me at this time.
> >
> > Rob
> >
> >
> >
> > --- On Sat, 1/10/09, lebofsky at lpl.arizona.edu <lebofsky at lpl.arizona.edu>
> > wrote:
> >
> >
> >> From: lebofsky at lpl.arizona.edu <lebofsky at lpl.arizona.edu>
> >> Subject: Re: [meteorite-list] Comet smashes triggered ancient famine ???
> >> To: rob_mccafferty at yahoo.com
> >> Cc: "tracy latimer" <daistiho at hotmail.com>,
> >> meteorite-list at meteoritecentral.com Date: Saturday, January 10, 2009,
> >> 11:47 PM
> >> While I have not read this book, generally, comets cannot
> >> hit the Earth over a short interval like SL9. SL9 was in orbit around
> >> Jupiter. It is
> >> highly unlikely that a comet could be captured in orbit around Earth.
> >> Continuous bombardment on Earth only happens in movies
> >> unless there is a massive swarm of objects (like in a meteor shower).
> >>
> >> The Earth is a moving target, so if one comet piece were to
> >> hit the Earth, it is unlikely that a second or third one in a similar
> >> orbit would hit, unless the cluster was VERY bunched together. The Earth
> >> would be long gone!
> >>
> >> The Earth's orbital velocity is about 30 km/s and its
> >> diameter is about 12,750 km. So the Earth moves its diameter in about 425
> >> seconds. If the comet pieces were farther apart than that, only one
> >> piece would hit.
> >>
> >> Larry
> >>
> >>
> >> On Sat, January 10, 2009 4:06 pm, Rob McCafferty wrote:
> >>
> >>> This is not a new idea. Mike Baille's book
> >>>
> >> "Exodus to Arthur" makes
> >>
> >>> interesting reading on the idea that comets may have
> >> triggered many human
> >>> catastrophies in the past. His book is based on
> >> dendochronology with
> >>> support from other sources. At the time of publishing
> >> c.2000, there was a
> >>> gap in the Greenland Ice core during the 6th Century.
> >>>
> >>> The first third of the book is compelling reading but
> >>>
> >> for me does little
> >>> to convince me that it was anything other than
> >> volcanic eruptions. The
> >>> latter part of the book is based on written accounts,
> >> myths and legends
> >>> to make a the suggestion that clusters of small comets
> >> may have been
> >>> involved, small fragments arriving in short interval
> >> like SL9 did on
> >>> Jupiter in 1994.
> >>> He's as objective as he can be but is clearly
> >>>
> >> convinced of the cometary
> >>> contribution in at least a few cases.
> >>>
> >>> Rob McC
> >>>
> >>>
> >>>
> >>>
> >>> --- On Fri, 1/9/09, tracy latimer
> >>>
> >> <daistiho at hotmail.com> wrote:
> >>
> >>>
> >>>
> >>>> From: tracy latimer <daistiho at hotmail.com>
> >>>> Subject: Re: [meteorite-list] Comet smashes
> >>>>
> >> triggered ancient famine ???
> >>>> To: "Paul" <bristolia at yahoo.com>,
> >>>>
> >> meteorite-list at meteoritecentral.com
> >>>> Date: Friday, January 9, 2009, 7:15 PM
> >>>>
> >>>>
> >>>>> From what little research I did, I had
> >>>>>
> >> understood that a
> >>>>>
> >>>> substantial chunk of the sun-blotting fog was
> >> actually 'vog', which
> >>>> outgassed from major eruptions in Iceland.
> >> Iceland underwent several
> >>
> >>>> periods of volcanic activity during the 'Dark
> >> Ages', where multiple
> >>
> >>>> volcanic vents burped out stifling clouds of gas.
> >> The gas periodically
> >>
> >>>> got so thick and noxious that it poisoned
> >> vegetation, killed animals,
> >>>> and sickened almost everyone else; there was at
> >> least one major exodus
> >>>> of survivors around 770 a.c.e.
> >>>>
> >>>> Tracy Latimer
> >>>>
> >>>>
> >>>>
> >>>> ----------------------------------------
> >>>>
> >>>>
> >>>>> Date: Fri, 9 Jan 2009 07:12:59 -0800
> >>>>> From: bristolia at yahoo.com
> >>>>> To: meteorite-list at meteoritecentral.com
> >>>>> Subject: [meteorite-list] Comet smashes
> >>>>>
> >> triggered
> >>>>>
> >>>> ancient famine ???
> >>>>>
> >>>>> Comet smashes triggered ancient famine
> >>>>> January 7, 2009 by Ker Than
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >> http://www.newscientist.com/article/mg20126882.900-comet-smashes-trigge
> >>
> >>>>
> >> red-ancient-famine.html?DCMP=OTC-rss&nsref=online-news
> >>>>>
> >>>>> Abbott, D. H., P. Biscaye, J. Cole-Dai, and D.
> >>>>>
> >> Breger,
> >>
> >>>>>
> >>>> 2008,
> >>>>
> >>>>
> >>>>> Magnetite and Silicate Spherules from the
> >>>>>
> >> GISP2 Core
> >>
> >>>>>
> >>>> at the 536 A.D. Horizon
> >>>>> American Geophysical Union, Fall Meeting 2008,
> >>>>>
> >>>>>
> >>>> abstract #PP41B-1454
> >>>>>
> >>>>>
> >>>>
> >> http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&rang
> >>
> >>>>
> >> e=1&directget=1&application=fm08&database=%2Fdata%2Fepubs%2Fwais%2Finde
> >>
> >>>>
> >> xes%2Ffm08%2Ffm08&maxhits=200&=%22PP41B-1454%22
> >>>>>
> >>>>> and
> >>>>>
> >>>>>
> >> http://adsabs.harvard.edu/abs/2008AGUFMPP41B1454A
> >>
> >>>>>
> >>>>>
> >>>>> Yours,
> >>>>>
> >>>>>
> >>>>>
> >>>>> Paul H.
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> ______________________________________________
> >>>>> http://www.meteoritecentral.com
> >>>>> Meteorite-list mailing list
> >>>>> Meteorite-list at meteoritecentral.com
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >> http://six.pairlist.net/mailman/listinfo/meteorite-list
> >>
> >>>>
> >> _________________________________________________________________
> >>
> >>>> Windows Live???????: Keep your life in sync.
> >>>>
> >>>>
> >> http://windowslive.com/explore?ocid=TXT_TAGLM_WL_t1_allup_explore_01200
> >> 9
> >>
> >>>> ______________________________________________
> >>>> http://www.meteoritecentral.com
> >>>> Meteorite-list mailing list
> >>>> Meteorite-list at meteoritecentral.com
> >>>>
> >>>>
> >> http://six.pairlist.net/mailman/listinfo/meteorite-list
> >>
> >>>>
> >>>
> >>>
> >>>
> >>> ______________________________________________
> >>> http://www.meteoritecentral.com
> >>> Meteorite-list mailing list
> >>> Meteorite-list at meteoritecentral.com
> >>>
> >>>
> >> http://six.pairlist.net/mailman/listinfo/meteorite-list
> >>
> >>>
> >>>
> >
> >
> >
> > ______________________________________________
> > http://www.meteoritecentral.com
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> >
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>
Received on Sun 11 Jan 2009 02:35:21 PM PST