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Farmington

Hello Martin, hello folks out there,

I could not resist :-)

OBERST J. (1989) Possible relationship between the Farmington
meteorite and a seismically detected swarm of meteoroids impacting the
Moon (Meteoritics 24-1, 1989, pp. 23-28):

Abstract - The Farmington ordinary L5 chondrite with its uniquely short
cosmic-ray exposure age of less than 25 000 years may have been a member
of a large meteoroid swarm which was  detected by the Apollo seismic
network when it encountered the Moon in June 1975. The association
implies that the parent body of the Farmington meteorite was in an
Earth-crossing orbit at the time the swarm was formed.  This supports
the idea that at least some meteorites are derived from the observable
population of Earth-crossing asteroids.

Geocentric radiant of the Farmington meteorite / Geocentric radiants,
all in degree

Event - Encounter time - Right ascension - Declination - Ecliptic
longitude - Reference

Farmington - June 25, 1890 - 87 (88,88,89) /    2 (6, 8, 9) - 86
(88,88,89) - Levin et al. (1976)
Farmington - June 25, 1890 - 81 (83,84,84) /- 18 (-11,-8,-7) - 79
(82,83,84) - Sekanina (1983)

Oberst computed the geocentric radiants for a range of possible
atmospheric entry speeds of 13 km/s and, in brackets, 16, 19, and 22
km/s, suggested for the Farmington meteorite (Levin et al., 1976).

CONCLUSIONS AND IMPLICATIONS

The fall time, the radiant and the exceptionally young cosmic-ray
exposure age of Farmington suggest that this meteorite was a member of
the large meteoroid swarm that was detected by the lunar seismic network
in June 1975. While the possibility that the Tunguska object was another
member of this swarm deserves further investigation, the previously
suggested associations of the lunar impacts with the Taurid meteor
complex and comet Encke or the postulated lunar impact event of  1178
appear unlikely.
This suggested association implies that the orbits of Farmington and the
other swarm members experienced very little perturbation after their
separation from their parent body or after the parent body disrupted.
Thus, it is most likely that the parent body was in an Earth-crossing
orbit at the time the swarm formed. This further supports the idea that
some of the meteorites in our collections are derived from the
observable population of  A p o l l o and  A m o r objects (Levin et
al., 1976;Wetherill. 1976).
If asteroid surveys can locate other large fragments or even the parent
body in the orbit of the Farmington meteorite, this would provide an
interesting link between laboratory studies of meteorites and the
astronomical studies of minor planets in the solar system, their
presumed parent bodies. If such an object can be found and can be
studied, it would be important to verify that its reflectance spectrum
is identical to the laboratory spectrum of Farmington. Perhaps, close
examination of the object could provide clues to some of the unresolved
mysteries involving the origin of ordinary chondrites, the origin of
Earth-crossing asteroids and the role of these asteroids for the
delivery of meteorites to Earth. Certain Earth-approaching asteroids
indeed show reflectance spectra similar to those of ordinary chondrites
in laboratories (McFadden et al., 1985).  However, why don't we see any
such asteroids in the main belt, the suggested source location of this
meteorite class?

Some more pertinent references:

BUSECK P.R., MASON B. and WIIK H.B. (1966) The Farmington meteorite
(Mineralogy and chemistry (GCA 30, 1-8).

DE FELICE J., FAZIO G.G. and FIREMAN E.L. (1963) Cosmic-ray exposure age
of the Farmington meteorite from radioactive isotopes (Science 142,
673-674).

GALIBINA I.V., SIMONENKO A.N. and LEVIN B.Y. (1979) The last parent body
of the Farmington meteorite remains undiscovered (Sov. Astron.  Lett. 5,
223-225).

Best wishes, Bernd