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

[lebofsky at lpl.arizona.edu]

Hi Doug:

This is one of many models for the capture and a very possible one.
However, from what I see of the obital evolution and the actual abstract,
I would say that prior to capture, in this model, SL9 was a Jupiter family
comet which is a far cry from an asteroid belt object (had to come close
to Jupiter multiple times).

The asteroid belt goes out to 3.3 AU, so not with nearly 2 AU of Jupiter,
not like the pre-capture SL9.

Larry
PS Never said it was a dramatic capture!

On Sun, January 11, 2009 10:50 am, mexicodoug at aim.com wrote:

> Larry wrote:

>

>

> "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."

>

> Hi Larry, Listees,

>

>

> IMO, it was far from that dramatic sort of initial Jovian fishing

> expedition in those passes, in that SL9, before it's chaotic Jupiter

> capture looked like one of our favorite kinds of asteroids with an orbit

> likely CONFINED inside the main asteroid belt and with sufficiently of low

> inclination (though with lower probability it could have been stuck a

> little further out, at most, into the zone between Jupiter and Saturn).

> While all short period comets like SLP have a

> pinball aspect to their orbits before getting stuck within, say, inside

> Neptune's orbit, SL9 just did what any meteoroid with potential would

> have done in that it got too close to Jupiter and stretched out its orbit

> like pulling a rubber band.  As this is thought to have happened right at

> aphelion, the comet was basically at a standstill when Jupiter bumbled by

> and it transferred into a Jovian orbit by basically falling into Jupiter

> in an extremely eccentric orbit (as you point out), and from there on,

> just got too close to Jupiter as Jupiter and the Sun ironed out tyheir

> differences without JPL pushing the comet's outgassing buttons.

>

> Here is a sc

> ienific eplanation and a graphical evolution of the capture orbits as

> calculated by astrophysicists: http://tinyurl.com/742lbr

>

>

> Of course, where SL9, or anything else for that matter before being in

> the e.g., asteroid belt, came from, whether 25 or 2.5 billion years

> earlier, makes for good philosophy.

>

> A minor sampling of thoughts on this event from a meteoritical

> perspective...and for all good hearted Comet-fearing humans:

>

> The collision of SL9 with Jupiter was a great event to have been alive

> to have observed, but should be put in the appropriate context regarding

> orbit dynamics and the inner Solar system (read: frequencies of collision

> with Earth).  While such a Jupiter collision may well be a once in 6000

> (as you suggested) year event, one very pleasing rigorous

> analysis concluded that such event:

>

> " In particular, we show that, for Jupiter-interacting* comets of

> greater than 1 km diameter, a Jupiter impact takes place every 500 to 1000

> years, and an Earth impact every 2 to 4 million years."

>

> The sort of study great pops the ballon of theories suggesting that

> comets frequently strike Earth (and shape evolution frequently in thousands

> or tens of thousands of years periods).  The important detail lies within

> the observation that the residence time for comets in the Terrestrial

> (inner) Solar system is so short and chaotic from an

> orbital perspective, and the planets so small (for example, see Larry's

> cross section , but he was actually waaaaay overestimating it since we

> need to also consider the inclinations of the comets), that there is

> virtually nil chance = 2 - 4 million years vs. what we saw happen on

> Jupiter.  Furthermore, what led to that collision, as has already been

> suggested is that Jupiter was able to capture the comet to start with. That

> is not something the Earth is adept at doing considering the relative size

> of the Sun and its gravitational potential vs. ours in the uptown part of

> the Solar neighborhood.  Here is the excellent statistical vs.

> observational treatise by T. NAKAMURA (National Astronomical Observatory,

> Japan) and H. KURAHASHI (Sano-Fuji Optics

> Company, Japan), THE ASTRONOMICAL JOURNAL, 115:848-854, Feb. 1998.

>

>

> http://www.iop.org/EJ/article/1538-3881/115/2/848/970144.html

>

>

> *ok, so have the wild card of hyperbolic comets and highly inclined

> rogue comets and the likes of the kitchen sink of things that don't fit

> nicely into the Solar system intro textbook.  Perhaps this provides some

> SOLice for the frequent Terrestrial-cometary collision proponents.

>

>

> Anyway, this is my take on it Larry, and it is based on oldies but

> goodies regarding the papers cited. I can't find, and don't know that

> anyone has done anything particularly revolutionary since then.

>

> Best wishes, great health and keep looking up,

> Doug

>

>

>

>

>

>

>

>

> -----Original Message-----

> From: lebofsky at lpl.arizona.edu

> To: ensoramanda at ntlworld.com

> Cc:20meteorite-list at meteoritecentral.com

> Sent: Sun, 11 Jan 2009 6:54 am

> Subject: Re: [meteorite-list] Comet smashes triggered ancient famine ???

>

>

>

>

> 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 othe rs 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

>>> 20c.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

>>>

> 0A>>

>

>>>>> 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 Liveâ„¢: Keep your life in sync.

>>>>>

>>>>>

>>>>>

>>>

> http://windowslive.com/explore?ocid=TXT_TAGLM_WL_t1_allup_explore_01200

>

>>> 9

>>>

>>>

>>>>> ______________________________________________

>>>>> http://www.meteoritecentral.com

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>>>>>

>>>>>

>>>>>

>>> http://six.pairlist.net/mailman/listinfo/meteorite-list

>>>

>>>

>>>>>

>>>>

>>>>

>>>>

>>>> ______________________________________________

>>>> http://www.meteoritecentral.com

>>>> Meteorite-list mailing list

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>>>>

>>>>

>>>>

>>> http://six.pairlist.net/mailman/listinfo/meteorite-list

>>>

>>>

>>>>

>>>>

>>

>>

>>

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