[meteorite-list] Comet May Have Missed Earth By A Few HundredKilometres in 1883?

From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Tue, 18 Oct 2011 00:59:56 -0400 (EDT)
Message-ID: <8CE5B69E9D6CBF3-1394-71C00_at_webmail-m022.sysops.aol.com>

We listees know the Mexican astronomer in this article, for another
reason - he is the one who managed to write up the account of the
Mazapil iron meteorite, which he also attributed to have come from
fragmenting Comet Biela in that same time frame. I'm from Missouri on
this one, as much as I would like to believe that Mexican skies are the
nicest in the world (which of course is not true anymore, but some are
still quite good).

I would put more creedence in this if I already wasn't pissed off at
the incredible description of dancing meteors he described durning the
fall of Mazapil, but, for all the detail, of sizzling iron, there was
absolutely no mention of which direction the fireball was observed.
Even at that time, a key piece of information that would have quenched
later debates about meteorites being larger cometary masses which was
widely believed or tolerated at that time.

Kindest wishes
Doug


-----Original Message-----
From: John Lutzon <jl at hc.fdn.com>
To: Ron Baalke <baalke at zagami.jpl.nasa.gov>
Cc: meteorite-list <meteorite-list at meteoritecentral.com>
Sent: Mon, Oct 17, 2011 8:53 pm
Subject: Re: [meteorite-list] Comet May Have Missed Earth By A Few
HundredKilometres in 1883?


Hi Ron,

Thank you again for all of your posts---very informative.

I just gave up drinking beer and burned my will---no need for such
trivia at
this point.

Does anyone have any data on this "Pons-Brooks" and/or are there any
calcs.
on its possible return to our backyard?

Well, maybe one more beer while i wait for the flash.

John.

----- Original Message -----
From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Sent: Monday, October 17, 2011 7:23 PM
Subject: [meteorite-list] Comet May Have Missed Earth By A Few
HundredKilometres in 1883?


>
> http://www.technologyreview.com/blog/arxiv/27264/
>
> Billion Tonne Comet May Have Missed Earth By A Few Hundred
> Kilometres in 1883
>
> Technology Review
> October 17, 2011
>
> A re-analysis of historical observations suggest Earth narrowly
avoided
> an extinction event just over a hundred years ago
>
> On 12th and 13th August 1883, an astronomer at a small observatory in
> Zacatecas in Mexico made an extraordinary observation. Jos?? Bonilla
> counted some 450 objects, each surrounded by a kind of mist, passing
> across the face of the Sun.
>
> Bonilla published his account of this event in a French journal called
> L'Astronomie in 1886. Unable to account for the phenomenon, the editor
> of the journal suggested, rather incredulously, that it must have been
> caused by birds, insects or dust passing front of the Bonilla's
> telescope. (Since then, others have adopted Bonilla's observations as
> the first evidence of UFOs.)
>
> Today, Hector Manterola at the National Autonomous University of
Mexico
> in Mexico City, and a couple of pals, give a different interpretation.
> They think that Bonilla must have been seeing fragments of a comet
that
> had recently broken up. This explains the 'misty' appearance of the
> pieces and why they were so close together.
>
> But there's much more that Manterola and co have deduced. They point
out
> that nobody else on the planet seems to have seen this comet passing
in
> front of the Sun, even though the nearest observatories in those days
> were just a few hundred kilometres away.
>
> That can be explained using parallax. If the fragments were close to
> Earth, parallax would have ensured that they would not have been in
line
> with the Sun even for observers nearby. And since Mexico is at the
same
> latitude as the Sahara, northern India and south-east Asia, it's not
> hard to imagine that nobody else was looking.
>
> Manterola and pals have used this to place limits on how close the
> fragments must have been: between 600 km and 8000 km of Earth. That's
> just a hair's breadth.
>
> What's more, Manterola and co estimate that these objects must have
> ranged in size from 50 to 800 metres across and that the parent comet
> must originally have tipped the scales at a billion tonnes or more,
> that's huge, approaching the size of Halley's comet.
>
> That's an eye opening re-examination of the data. Astronomers have
seen
> a number of other comets fragment. The image above shows the
> Schwassmann-Wachmann 3 comet which broke apart as it re-entered the
> inner Solar System in 2006. There's no reason why such fragments
> couldn't pass close by Earth.
>
> One puzzle is why nobody else saw this comet. It must have been
> particularly dull to have escaped observation before and after its
close
> approach. However, Manterola and co suggest that it may have been a
> comet called Pons-Brooks seen that same year by American astronomers.
>
> Manterola and co end their paper by spelling out just how close Earth
> may have come to catastrophe that day. They point out that Bonilla
> observed these objects for about three and a half hours over two days.
> This implies an average of 131 objects per hour and a total of 3275
> objects in the time between observations.
>
> Each fragment was at least as big as the one thought to have hit
> Tunguska. Manterola and co end with this: "So if they had collided
with
> Earth we would have had 3275 Tunguska events in two days, probably an
> extinction event."
>
> A sobering thought.
>
> Ref: arxiv.org/abs/1110.2798 <http://arxiv.org/abs/1110.2798>:
> Interpretation Of The Observations Made In 1883 In Zacatecas
(Mexico): A
> Fragmented Comet That Nearly Hits The Earth
>
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Received on Tue 18 Oct 2011 12:59:56 AM PDT