[meteorite-list] Mbale

From: bernd.pauli at paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: 16 May 2007 19:33:53 UT
Message-ID: <DIIE.000000BF00001A15_at_paulinet.de>

Hi AL, Martin and all,

> There was a good article about the fall in S & T with good photos.

Best regards,

Bernd

Sky & Telescope, June 1983, pp. 96-97
Amateur Astronomers, Edited by Stephen James O'Meara

On August 14, 1992, a daytime shower of stony meteorites rained down on Mbale,
Uganda, and its surroundings. Clockwise from left: These Ugandan soldiers collected
two fragments with weights of 6.2 and 3.0 kilograms, respectively. Three men from the
tiny village of Malukhu found a 10.8-kg fragment that made an 85-cm-deep hole when
it hit. A sample of meteorites recovered from the Mbale fall and outlying regions; the total
weight of these fragments exceeds 40 kg. All photographs, unless credited otherwise, are
by Jan L. Betlem, Mount Elgon Conservation and Development Project.


The Day That Rained Stones

On the afternoon of August 14, 1992, citizens of Mbale, Uganda, witnessed a large explosion
in the sky, out of which emerged a shower of flaming meteorites. For minutes the fragments
rumbled as they blazed smoky trails across the heavens. Villagers farther north thought they
were being bombed by rebels, since conflicts were occurring only a few tens of kilometers
away - in the direction from which the objects came! Adding to the confusion, the explosion
produced a sonic boom that sounded like machine-gun fire. Minutes later stones showered
the Earth.
The next day Jan L. Betlem of the Mount Elgon Conservation and Development Project in
Mbale informed the Dutch Meteor Society of the fall. On August 25th I arrived in Africa with
fellow meteor-society members to interview eyewitnesses and study impact sites. Already the
police had inherited a fine collection of fragments, one of which weighed about a kilogram.

For a week we carried out fieldwork with geologists Thomas Schl?ter and Erasmus Barifaijo
(Makarere University of Kampala, Uganda) and local authorities. Police also assisted, leading
us to several buildings hit by meteorites in Mbale's industrial area. During our inspection we
also found several other impact sites.
To date we know of about 50 impacts. Two major ones took place in the swamps south of a
prison. In fact, four fragments fell near or hit the prison itself. The largest, weighing at least 10 kg,
landed only one meter from a building near the prison and made a depression 80 centimeters deep.

Two meteorites smashed into a railway station; one broke through its roof and shattered on the
concrete floor. Another impact occurred at a Shell Oil Co. storage facility. The stone, weighing
a few kilograms, fell atop an underground fuel tank; fortunately it produced a hole only a few tens
of centimeters deep. Another major fragment weighing about 5 kg pierced the roof of a cotton
factory, hit a machine, and shattered into several piece. Impacts were also reported at a coffee
factory and a sewage works northwest of Mbale.
Smaller fragments were found in Doko, about 5 km northwest of Mbale, where we recovered
many stones weighing a few grams. As far as we know, no one was injured during the falls
- incredible considering the dozens of meteorites that must have rained down on that densely
populated area. A 4-gram fragment did hit a boy from Doko on the head, but he was not hurt.

The meteorites speak

About 300 kg of meteorites fell on Mbale and its environs. Although we probably recovered all
of the major fragments, many of the smaller stones might still lie at the bottom of the extensive
swamps surrounding the city; these might never be recovered. The weight of the collected
fragments ranged from 0.1 gram to several tens of kilograms.

The Mbale meteorites are now being studied in the Netherlands. Initial research by C.E.S. Arps,
director of mineralogy at the National Museum of Natural History in Leiden, indicates that they
are L6 type chondrites - stony objects low in iron with microscopic flecks of magnesium-iron
silicates. Larger fragments show thin, annealed fractures, implying that the final breakup took
place high in the sky. In fact, nearly all of the 300 recovered fragments have a black fusion crust.

Eyewitness accounts of the explosion are sketchy, mainly because it occurred high in the sky near
the Sun. We believe that the final breakup occurred about 10 km north of the major impact sites
we inspected. The fireball's flight angle and duration, however, are still very uncertain. By weighing
the fragments and studying the impact sites further we hope to learn more about the parent body's
course.

HANS BETLEM, Dutch Meteor Society, Lederkarper 4, 2318 NB Leiden, The Netherlands
Received on Wed 16 May 2007 03:33:53 PM PDT