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(meteorobs) Meteor explosions
A recent post on the astro list pertaining to other possible Tunguska type
explosions is forwarded below.
George Zay
---------
>
>In a recent post, Robert G Fenske Jr <fenske@rgfpc.electro.swridot edu> notes:
>
>>The messages about Jupiter strikes brings to mind that some Monks
>>in 1178 AD apparently witnessed the impact that created the crater Bruno
>>on the Moon. This event was noted in a short segment of the Carl Sagan's
>>Cosmos series of the early '80s.
>
>It reminded me of an article that I printed in our society newletter in
>December, 91. The author, Dan Durda, is now a Ph.D. graduate from UF and
>last I heard was working in the planetary sciences dept at the University
>of Arizona. He has contributed several articles to Astronomy magazine on
>the subject of asteroids.
>
>Believe me that I am not trying open old wounds with this reprint. Take
>this as an interesting speculation which might bear further discussion.
>
>-------------------------------------
>
>A Possible New Zealand "Tunguska"
>by Daniel D. Durda, University of Florida, Dept. of Astronomy
>
>[Editor's note: This article is devised from a message found on the
>Astronomical Society of the Atlantic (ASA) BBS. Mr. Durda attended the
>meeting of the Division of Planetary Sciences which was held in Palo
>Alto, CA. in the first week of November. In his message he shared
>information about a New Zealand impact hypothesis, which (in his words)
>"I am neither advocating nor bashing."]
>
>Let me first summarize from a preprint of a paper that Duncan Steel
>gave me. The paper is titled "The Tapanui region of New Zealand: a
>Tunguska' of 800 years ago?" by Duncan Steel and Peter Snow. Some of
>this will be practically verbatim: First they provide some evidence
>supporting the fact that the Earth is struck quite frequently by
>astronomical objects. The frequency of encounters with an object capable
>of producing a Tunguska-like explosion is of the order of every few
>centuries or so (Morrison and Chapman, 1989), although the data on which
>these rates are based are fuzzy.
>
>They suggest that the southern part of the South Island of New Zealand
>may have been the target of such a projectile about 800 years ago or so
>and that scientific study of the region is warranted.
>
>Near the town of Tapanui in the province of Otago is a structure known
>as the Landslip Crater or Landslip Hill (169" 09' east, 460 04' south).
>This is an incomplete ovoid 900 by 600 by 130 meters deep. Geological
>interpretation of the feature points to it being a landslide and not an
>impact scar (Lindquist, 1990). (Gene Shoemaker told me that he agrees
>with this interpretation. If anyone can recognize an impact scar it's
>Gene!). Although most likely not an impact scar, Steel and Snow state
>that there is prima facia evidence that links the site to a
>cataclysm about 800 years ago. There were widespread fires about that
>time that are usually attributed to the Maoris burning the forests to
>drive the now-extinct Moas into the swamps, where many Moa remains are
>now found. Carbon dating of the charcoal that pervades the soils of the
>southern provinces gives dates of 600-1000 years ago with a clustering
>of dates about 800 years ago. The upshot is that there seems to be a
>distinct link between the fires and the extinction of the Moas.
>
>"However, there is some evidence that indicates a rather more coherent
>event: "The tree fall distribution from that period apparently points
>radially away from the Tapanui site (Snow, 1983). Pajac (1989,1990)
>claims that this pattern extends radially away from the site to
>distances of 40-80 km. Pajac also states that trinitites, small globules
>of silicates, are found in the region and indicate a cataclysmic
>explosion. (He attributes this to the crash of an extraterrestrial
>spacecraft! 'I can think of less exotic explanations!). There are
>also a lot of sarsons or Chinamen stones scattered around, being
>composed of quartz sandstone. Pajac believes these have been
>metamorphosed under high temperature and pressure. Lindquist (1990)
>identifies them as being made of fluvial quartz sandstone and
>conglomerates which have been silica-cemented.
>
>There is evidence of Maori myth, legend, poetry, and song which speak
>of the falling of the skies, raging winds, upheaval of the Earth, and
>mysterious devastating fires from space. Tapanui itself apparently means
>`The big explosion' or 'The big devastating blow'. The Maori have a
>saying: "The history is in the names, and the names are in the land". A
>nearby site is Waipahi, which may be taken to mean "The place of the
>exploding fire". Other similar place names exist which do not appear
>commonly in other places in New Zealand.
>
>Maori mythology is rife with connections between these fires, the
>end of the Moas, and an object falling from the Moon or space. The word
>Moa is recent; in the early Moa hunter epoch before the flames the Maori
>called the bird Pouakai, but afterwards it was called Manu Whakatau, one
>translation of which is The bird felled by strange fire'. Here's a Maori
>poem:
>
>Very calm and placid have become the raging billows
>That caused the total destruction of the Moa
>When the horns of the Moon fell from above down
>
>The idea that the Moa died in some natural fire is not a new one. There
>are arguments for the demise of the North Island Moa due to a volcanic
>eruption or something similar; a report of a conversation with an 88
>year old Maori chief: "The Moa disappeared after the coming of Tamaatea
>(a man/god) who set fire to the land. The fire was not the same as our
>fire but embers sent by Rongi (the sky). The signs of the fires are
>still to be seen where red rocks like berries are found;" The Chinamen
>stones often appear red when freshly exposed.
>
>As a baseline hypothesis, Steel and Snow adopt the hypothesis that the
>structure at Tapanui is the scar produced by the detonation of a large
>bolide in the atmosphere (like the Tunguska Event) and the forest fires
>were ignited by this event. Steel advances the hypothesis that in the
>current epoch the Earth is subject to a substantial flux of debris
>associated with the breakup of a large comet in the past 10,000-20,000
>years. The various phenomena now associated with this breakup (recurrent
>meteor showers, P/Comet Encke, several Apollo asteroids) are
>collectively termed the Taurid Complex. He and his collaborators believe
>that the core of this complex intersects our planet, under orbital
>precession, for four periods lasting a century or so, these four periods
>being spread over a cycle time of a few thousand years (Steel, et al.,
>1991)
>
>One such period was apparently near the start of the present millennium
>and so coincides with proposed entry of the bolide over New Zealand.
>This also coincides with the timing for the formation of the crater
>Giordano Bruno on the Moon and the Canterbury Event of June 25, 1178.
>(Steel told me that it was the coincidence in timing between the
>Canterbury Event and the New Zealand fires that got them thinking
>about all this). Another place name is Otarehua, where 'Ota' means 'of
>the' and `rehua' was the Maori name for Antares, the (northern) summer
>star. This may help place the time of year when the event occurred:
>perhaps near northern mid-summer, when the daytime Taurid intersection
>with the Earth is most active and the Tunguska Event occurred. Other
>place names may be of use in indicating the day in the lunar cycle when
>the event occurred.
>
>References (just some of those given by Steel and Snow):
>
>Lindquist, JK (1990) New Zealand J. Geol. Geophys., 33, 137-150.
>Morrison, D and Chapman, CR (1989) Cosmic Catastrophes, Plenum
>Press, NY.
>Pajac, J (1989) Tapanui Cataclysm - An Explanation for the Mysterious
>Explosion in Otago, New Zealand, 1178 A.D., ISBN 0-9597698-7-0, 62
>PP , Privately printed by the author, 116 Rolla Street, NEV,
>Dunedin, New Zealand.
>Pajac, J (1990) Ancient Skies, 17, #4.
>Snow, PG (1983) The Mystic Fires of Tamaatea, unpublished manuscript.
>Steel, D I, Asher, D J, and Clube, S V M (1991) The structure and
>evolution of the Taurid Complex, Mon. Not. Roy. Astron. Soc., (in
>press).
>
>There you have it. Daniel Fischer was kind enough to point out to me
>that there has been a discussion going on in the Journal of the British
>Astronomical Association concerning the Canterbury Event: just what
>happened there? Lunar impact or simple atmospheric effects on a slim
>crescent Moon? This in and of itself can be a subject of much
>discussion. Interesting because it obviously has some connection with
>the hypothesized Tapanui Event.
>
>---------------------
>Roger D. Curry <rcurry@southeastdot net> 30.2N/81.4W
>Visit the Northeast Florida Astronomical Society Home Page at
>http://users.southeastdot net/~rcurry/nefas.html
>
>