[meteorite-list] Did a Collision Cause Comet 17P/Holmes'MysteriousOutburst?

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 7 Nov 2007 23:14:50 -0600
Message-ID: <0a5301c821c6$4a906f40$c944e146_at_ATARIENGINE>

Hi, Jerry,

    Credit where credit is due! Larry Lebofsky used the
expression "burp" on the List when arguing for a gas
explosion from perihelion warming when I was arguing
for a collision (before visualizing that orbit completely),
so I began to think of these two causes as the "Bump"
and "Burp" Theories.

    Of course, you can have the "Unified Bump and Burp"
Theory, in which a collision exposes a big area of volatiles
out where things are so cold it doesn't matter, but then later,
when the comet comes its closest to the Sun, the volatiles
cook up and start to boil away in a big jet that spreads gas
and dust in every direction as the comet spins.

    That makes three Theories. A fourth Theory is that there
are internal processes possible in comets that are exothermic,
that is, that it is possible that icy bodies can have a kind of
cryovulcanism that causes outgassing and the development
of a coma. The more we observe the smallish icy bodies of
the outer solar system, like at Saturn, the more unexplained
internal processes we see in action.

    A fifth Theory involves the unpredictable behavior of the
debris streams that travel with a comet, rubble that spreads
along the entire orbital path in clumps that migrate along the
orbit by perturbation and may collide with the body that
spawned them and expose new volatiles (as in the third
Theory). These debris stream are common; all our meteor
showers are from the debris streams of appropriately placed
comets.

    Comet Holmes can easily spare these few millions of
kilos of material that it's spewing into the coma. Its volume
is roughly 20,575,000,000 cubic meters. If it's ice with a
density of 1.0, that's 20,575,000,000 tons. Comet Holmes
can spare a few million tons, much less kilos. Comets are
just litterbugs.

    And please, Jerry, don't even joke about an impact with
a "little" comet like Comet holmes which fortunately does
not come into the inner solar system even as far as Mars.
If Holmes had an "Earth-grazing" orbit with perihelion at
or inside the orbit of the Earth with a potential of collision,
it would be a Bad Thing.

    A little calculating yields a 3,000,000 MegaTon impact
which leaves a 25-mile crater 3000 feet deep. The 17-mile
diameter fireball is 19 times brighter than the Sun. The impact
is not survivable closer than about a 120-mile radius and
the radius of more or less total destruction of works and
infrastructure is 300 to 350 miles. It takes out a smallish
continent-sized chunk of the environment, about half the
size of Europe... or six times the size of Texas. It's the
sort of thing that happens every 10 million years or so.

    The comet is pretty right were it is. Let's leave it there.


Sterling
-------------------------------------------------------------------------
----- Original Message -----
From: "Jerry" <grf2 at verizon.net>
To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>; "Meteorite Mailing
List" <meteorite-list at meteoritecentral.com>
Cc: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
Sent: Wednesday, November 07, 2007 9:09 PM
Subject: Re: [meteorite-list] Did a Collision Cause Comet
17P/Holmes'MysteriousOutburst?


Sterling, Larry and List,
The "burp" theory as proposed by Sterling is as solid as any and more likely
than most to guesstmate the auspicious, unusual cometary event that graced
this generation of observers with a front row seat to the great mysteries of
OUR existence. We, once more, have been priviledged to witness a spectcal to
generate wonder. Whether, and I doubt we'll ever explain this one, a
consensus is ever arrived at, I am satisfied that the collisional aspect has
been addressed and though partitioned into a much lower probability,
uncertaintity, chaos if you will, has reared its head to grade our fears and
futures into a more respectable framework to wend our way through the rest
of our days.
Spooky, but throw in a Nakhla Dog, a Lama or two, a guy blow off his feet
and knoked unconscious, another at Tunguska and IT does give one pause.
Jerry Flaherty
----- Original Message -----
From: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Cc: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
Sent: Wednesday, November 07, 2007 9:42 PM
Subject: Re: [meteorite-list] Did a Collision Cause Comet
17P/Holmes'MysteriousOutburst?


> Hi, List,
>
> You would think with all the new (and old) scientists
> examining the collisional possibilities of Comet Holmes
> passing through the Asteroid Belt, some of them might
> have noticed that Comet Holmes DOES NOT PASS
> "through" the Asteroid Belt!
>
> I'm being sarcastic about this because I made exactly the
> same mistake myself, until an astronomer, List member
> Larry Lebofsky, pointed out that because of its high inclination
> (19.12 degrees), Comet Holmes does not pass through the
> ecliptic plane in the Asteroid Belt, but way out at the inside
> edge of Jupiter's orbit, at 4.86 AU.
> http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=17p&orb=1
>
> The vast majority of the asteroids in the Main Belt have
> inclinations of less than 19 degrees. Of course, it is possible
> that Holmes could collide with a "less inclined" asteroid; it
> depends on the orientation of the asteroidal orbit. But, but it's
> really a very thin chance, with a small subgroup of an already
> widely scattered population. In non-numerical terms, Comet
> Holmes essentially passes over (and under) the Asteroid Belt,
> rather than "through" it.
>
> However, Holmes does plunge through the ecliptical plane
> in the position where thousands of Jupiter Trojan asteroids
> co-orbit with the planet, making passes that repeat the same
> orbital configuration every 81-point-something years. The
> odds of a collision with something in Jupiter's Trojans is
> dramatically higher than with a Main Belt asteroid.
>
> There are two goups of Trojans, ahead and behind Jupiter
> at 60 degrees, but since they are themselves generously
> distributed ahead and behind their Trojan points, along about
> 1/3rd of the Jupiter orbit, Holmes is exposed to such "Trojan"
> encounters for about 1/3rd of its orbits.
>
> The two possible causes of the outburst, collision or thermal,
> can be summarized as the "Bump" or "Burp" theories. I think an
> endogenous cause of the outburst is more likely than a collision,
> as both the great outbursts, the discovery outburst and the present
> one, occured after perihelion passage with some delay. From June
> 16, 1892 to November 6, 1892 is 143 days. From May 4, 2007
> to October 24, 2007 is 173 days. (There are some uncertainties
> about dates of perihelion.) Passage through the ecliptic plane at
> 2.05 AU (right at the inner limit of the Asteroid Belt) occurs 4-5
> months earlier than perihelion. At the times of the outbursts, the
> comet was high above the ecliptic plane (the ecliptic plane being
> where collisions would be most likely).
>
>
>
> Sterling K. Webb
> ---------------------------------------------------------------------------
> ----- Original Message -----
> From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
> To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
> Sent: Wednesday, November 07, 2007 5:46 PM
> Subject: [meteorite-list] Did a Collision Cause Comet 17P/Holmes'
> MysteriousOutburst?
>
>
>
> http://www.newscientist.com/blog/space/2007/11/did-collision-cause-comet-holmess.html
>
> Did a collision cause comet's mysterious outburst?
> Kimm Groshong
> New Scientist space blog
> November 06, 2007
>
> Comet 17P/Holmes has certainly given sky-watchers - backyard and
> professional astronomers alike - a thrilling chance to see a cometary
> outburst on a grand scale. After we posted my story
> <http://space.newscientist.com/article/dn12880> about on-going
> speculation about what could have caused this outburst (and the one 115
> years ago), many readers posted comments related to two questions: Could
> this have been triggered by a collision with an object in the main
> asteroid belt? And why can't we see more of a tail on this comet?
>
> Here's what I found out: Michael Mumma at the Goddard Center for
> Astrobiology says such a collision in the asteroid belt is theoretically
> conceivable. He noted that comet guru Fred Whipple suggested that a
> collision with a small asteroid could have provided the right amount of
> energy to produce the ejecta and brightening observed in the comet's
> 1892 flare-up.
>
> But Mumma himself thinks it would be "very surprising" if a collision
> were the cause of the outburst. He says part of the difficulty in
> weighing this possibility is that it's very hard to estimate how many
> small boulders are in the asteroid belt. These tiny objects - on the
> order of one-metre across - are beyond the detection limits of telescopes.
>
> Brian Marsden, former
> director of the International Astronomical Union's Minor Planet Center
> <http://cfa-www.harvard.edu/iau/mpc.html>, says plainly that he doesn't
> believe this to be a viable explanation for the outburst. He says it's
> hard to believe that this comet, among all those that pass through the
> asteroid belt, has been struck twice by objects in the belt - once in
> 1892 and again this year.
>
> Many people have been discussing whether or not this comet has a tail.
> Comets typically have two types of tail - a
> dust tail and an ion tail. The dust tail is made of fine dust from the
> comet's main body, or nucleus, that has been swept out by the Sun's
> radiation. It usually points in the direction from which the comet came.
> The ion tail is caused by the Sun's magnetic field sweeping ions (which
> start out as neutral gas particles on the body of the comet) into a line
> that always points directly away from the Sun.
>
> Marsden says the there isn't much of either type of tail. He says it's
> possible that there just isn't enough very fine dust in the material
> coming off the nucleus to be pushed by sunlight into a nice dust tail.
> (He says there may only be "fairly hefty dust" in the comet's coma.)
>
> Some people have argued that we can't see the comet's ion tail because
> the orientation of the Sun, Earth and comet means the tail is mostly
> pointing away from Earth.
>
> But though the tail does look fore-shortened, Mumma says the accumulated
> surface brightness would be greater seen from one end than if it were
> seen spread out, from the side. He likened it to looking at the contrail
> of a plane. If we saw the stream from the side, we would basically see
> right through it. But if we were in front of or behind the contrail,
> looking into it, it would appear many times brighter.
>
> Marsden says the comet is so far from the Sun that the solar wind is not
> interacting strongly enough with the ionised gas to produce a fantastic
> ion tail. But he says it doesn't bother him that it doesn't have much of
> a tail. After all, the "fuzzy head" is putting on such a great show of
> its own.
>
>
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Received on Thu 08 Nov 2007 12:14:50 AM PST