[meteorite-list] THE RECENT METEORITE FALL IN LORTON, VIRGINIA, USA.

From: Shawn Alan <photophlow_at_meteoritecentral.com>
Date: Fri, 30 Jul 2010 19:59:27 -0700 (PDT)
Message-ID: <864663.53408.qm_at_web35406.mail.mud.yahoo.com>

Hello Listers,

Here is the 73rd Annual Meteoritical Society Meeting (2010)abstract pertaining to the Lorton fall in April 2010.

?
THE RECENT METEORITE FALL IN LORTON,
VIRGINIA, USA
C. M. Corrigan1 L. C. Welzenbach1, M. Fries2, T. J. McCoy1, and
J. Fries3. 1Dept. of Mineral Sciences, National Museum of Natural
History, Smithsonian Institution, Washington DC, USA.
2NASA Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena,
CA, 91109, 3U. S. Air Force Weather Agency, 1st Weather
Group, Offutt AFB, Omaha, NE, 68113, USA. E-mail: corriganc_at_
si.edu.
?
?
Introduction: On Monday, January 18, 2010, a large fireball
was reported by viewers in the greater Washington, DC, USA,
area. Viewers from as far away as West Virginia have described
seeing a large, single fireball at 5:45 PM, near dusk that evening,
with some reporting having heard a large detonation. One stone
has been recovered to date, that having fallen through the
roof/ceiling of the Williamsburg Square Family Practice in Lorton,
VA. The doctors, who were in the office at the time the meteorite
fell, found the meteorite embedded into the concrete floor
(under the carpet). It had broken into three large pieces, along
with a few smaller fragments upon impact with the floor. The
doctors describe hearing a sound akin to bookshelves crashing to
the ground as the meteorite fell through the ceiling. This meteorite
fall, the first fall on record in the DC area (nearest being
Richmond, VA, 1828; St. Mary?s County, MD, 1919; and
Sharps, VA, 1921, M. Grady, Catalogue of Meteorites), and
who?s fireball was seen by many people on their evening commute,
garnered an enormous amount of public/media interest.

The meteorite: The meteorite in question was brought to the
Smithsonian Institution on Wednesday, January 20, for identification/
classification purposes. The meteorite is approximately 8
cm x 5 cm x 5 cm, and is roughly rectangular, with a dark, matte,
fusion crust. The meteorite contains a few small clasts visible on
the broken surfaces. The interior is, not surprisingly, exceptionally
fresh, with no evidence of oxidation of the metal grains. The
metal grains are very small and evenly distributed throughout the
rock. A few small (2 mm) relict chondrules are visible with the
naked eye. The total mass recovered is 329.7 grams.

Petrography and Mineral Chemistry: This new meteorite
is an L6 chondrite. Olivine composition is Fa: 24.7 ?0.3 (n=23).
Pyroxene composition is Fs: 20.9 ? 0.3, Wo 1.6 ?0.2 (n=16).
Feldspar composition is An: 10.3 ? 0.3, Or 6.4 ?2.8 (n=14). This
meteorite shows irregular fractures, but no undulous extinction in
the olivine grains, and is, therefore, shock stage S1. No shock
veins are present. Chondrules are rare, but when present, show
diffuse outlines and some degree of recrystallization, with many
crystals exhibiting 120-degree triple junctions. Metal and sulfide
occur mostly as separate, blocky, grains found throughout the
meteorite

Doppler Weather Radar: The Lorton fall appears in radar
data collected by the KLWX radar at Dulles Int'l Airport, in four
separate radar sweeps. [1,2] First appearance of falling debris
occurs at 2246:26 UTC and 3357m above local ground level.
Three additional radar returns occur between 2529m down to
466m above local ground level, with the last appearance seen at
2249:00 UTC. Radar return locations suggest that a strewn field,
if it exists, would extend from the single stone's fall site towards
a compass heading of ~83? for a distance of ~16km, although
much of this material may be small.

References: [1] Fries M. and Fries J. MAPS, In press.
[2] Fries M. and Fries J. LPSC 40, #1179.
?
http://www.lpi.usra.edu/meetings/metsoc2010/pdf/5353.pdf
?
Shawn Alan
IMCA 1633
eBaystore
http://shop.ebay.com/photophlow/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p4340
Received on Fri 30 Jul 2010 10:59:27 PM PDT