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Re: (meteorobs) Tunguska bolide & Beta taurid stream



Hello List!
Reference meteorites with known orbits: Last count I have for recovered meteorites for which orbits were calculated are Peekskill, Farmington, Innisfree, Pribram, Lost City and Dhajala (6 total).  All were ordinary chondrites, all had highly elliptical orbits with aphelia between Mars and Jupiter. All but Pilbram had an aphelia within the asteroid belt.  Peekskill had the most inclined orbit. 

Peekskill's data came form some 6-8 home videos which captured the long flight from Kentucky to over Easton, Pennsylvania over New Jersey and into a parked car in Peekskill, NY.  Of over 70 fragments identified in the video only one was recovered.

To my knowledge there have been "zero" meteorites recovered which can be associated with a meteor shower.  Murchison (September 28,1969 Lat: 36 ° 37'S Lon: 145 ° 12'E) a CM Carbonaceous Chondrite was originally suspected of cometary association for several reasons; most notably its high water and amino acid contents.  Current thought is that it came from one of 2 of several C-type asteroids in resonances capable of supplying fragments to earth.
( Sources: McSween, Weir)
BTW  Good info Jim on cometary debris characteristics, I have been looking for that data! Thanks!

Regards,
Elton Jones

Jim Bedient wrote:
> 
> At 01:07 PM 6/26/99 EDT, George wrote:
> 
> > GeoZay>>Also when I consider the lack of meteorites from cometary meteor
> >showers, they seem too fragile to get to the lower levels of the atmosphere to produce sonic booms  as the smaller yearly tunguska-like  explosions do.<<
> >
> > G. Kelly>>A good point.   Has anyone, anywhere, to anyone's knowledge, ever
> >recovered a meteorite that could definitely be linked to a meteor shower?
> >  >>
> >
> >This jogs another thought. There has been a number of multi station
> >photographic Fireball networks in existence....also some no longer operating
> >that has detected a number of Fireballs that has dropped recovered
> >meteorites. From these photographs, the orbits of recovered meteorites has
> >been determined. Has any of these ever indicated that the objects came from
> >an area other than the asteroid belt? Has any multi station fireball
> >photographs where meteorites haven't been recovered and were not part of a
> >recognized meteor shower been shown to come from anywhere other than the
> >asteroid belt? If some where detected, roughly what percentage of Asteroidal
> >origin vs something that could be considered short orbit comet parentage?
> >GeoZay
> 
> I hate it when questions like this pique my interest... I typically lose a
> whole morning surfing the NASA Astrophysics Data System
> (http://adswww.harvarddot edu/) researching the answer that I "think" I know!
> 
> Fireballs photographed from multiple sites are broken down into four major
> types according to their penetration depths into the atmosphere, ablation
> coefficient, density, and terminal velocity: Type I fireballs, the ordinary
> chondrites; Type II fireballs, the carbonaceous chondrites; Type IIIa
> fireballs, high density cometary material; and Type IIIb fireballs, low
> density cometary material.  Recognize that there is a bit of a disconnect
> here: the classifications are largely theoretical, since the direct
> comparison of well-observed fireballs and their eventual meteoritic product
> has been extremely limited.  They are very well established by the
> comparison of the physical characteristics of "found" meteorites and the
> inferred physical characteristics of fireball events in the atmosphere;
> still, the set of well observed falls is vanishingly small.
> 
> There have only been three recoveries from the major photo networks:
> Pribram, Innisfree, and Lost City, all of which were ordinary chondrites
> produced by Type I fireballs from asteroidal orbits.  Ceplecha (Ceplecha
> Z., 1988, Bull. Astr. Inst. Czech., 39, 221) in an analysis of photographic
> and television data from multiple stations for 3624 sporadic meteors found
> that 38% of fireballs come from cometary orbits (11% from highly eccentric
> orbits typical of new comets), but most of the fireballs (62%) originate at
> asteroidal orbits.  The standard explanation is that the denser asteroidal
> material is more likely to survive an atmospheric transit than "weak"
> cometary material.
> 
> The picture of the origin of each type is well and truly muddied by all the
> comet-asteroid transition objects that have been discovered recently,
> attempts to correlate other sources of data on interplanetary dust
> particles (IDPs) with fireball and meteorite data, and evidence for the
> existence of groups of meteorite-producing asteroidal fragments - meteorite
> streams.
> 
> Halliday et al (Meteoritics, vol. 25, June 1990, p. 93-99) found evidence
> among 89 potentially meteorite-producing MORP and Prarie Network events for
> four separate "streams" of asteroidal fragments.
> 
> Jakes and Padevet ("Meteorites, Bolides and Comets: A Tale of
> Inconsistency", Meteoritics, vol. 27, no. 3, volume 27, page 238) compare
> photo network data with recovered meteorites, and examine two extreme
> hypotheses: A, that only dense (Type I and II) fireballs produce
> meteorites, or B, that all four types (I, II and the less dense types IIIa
> and IIIb) produce meteorites.  Hypothesis A fits the observed data best if
> it is assumed that all four types tend to fragment at the same rate in the
> atmosphere; Hypothesis B fits the observed data best if it is assumed that
> the less dense bodies fragment more rapidly (which I think is supported
> well in the literature elsewhere).
> 
> They conclude, with reference to hypothesis B: "Correlation of bolide
> properties with meteorite falls could well be accommodated by the
> hypothesis B in which each bolide type has a meteorite equivalent. This
> has, however, some "outrageous" implications: comets may carry chondrites,
> icy dust balls do not produce fireballs; the extremely primitive
> carbon-rich particles represented by the IDPs do not form larger discrete
> bodies (fireballs) of "asteroidal" size; and the asteroid belt is a mixture
> of "native fractionated old bodies" together with the captured comets.
> Hypothesis B therefore contradicts the "established" scheme of the asteroid
> belt in which the non-differentiated meteorites (CI, CM, and CV) form the
> outer part of the asteroid belt, whereas the fractionated metamorphosed and
> igneous meteorites characterize the inner asteroids."
> 
> H. Campins and T.D Swindle have published ("Are There Cometary
> Meteorites?", 29th Annual Lunar and Planetary Science Conference, March
> 16-20, 1998, Houston, TX, abstract no. 1004) a list of traits that they
> believe should be characteristic of a cometary-origin meteorite:
> 
> 1. Rare (as rare as carbonaceous chondrites)
> 2. Dark (about 5% geometric albedo)
> 3. Weak (~10^7 dynes/cm^2)
> 4. High porosity, low density
> 5. Highly unequilibriated Fe/(Mg+Fe) in silicates
> 6. Nearly Solar elemental abundances
> 7. High abundance of C, N, and organics
> 8. Anhydrous silicates
> 9. More likely than asteroidal meteorites to contain interstellar grains
> with peculiar isotopic ratios
> 10. Likely not to have chondrules
> 11. Unremarkable cosmic ray exposure ages (~10^7 years)
> 12. and 13. Chemical differences due to cosmic ray exposure.
> 
> As is typical in the complex system we inhabit, the answer is not easy, and
> not yet entirely clear.  That is what keeps us all interested though, no?
> 
> JB
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