Vaca Muerta
Location: Vaca Muerta, Atacama, Chile, 25º 45'S, 70º 30'W (or 25°50'S, 70°23'W) 60 km S.E. of Taltal, Atacama desert, Chile
Strewnfield: 11.5 km long, 2.1 km wide
Found: 1861.
Type: Mesosiderite A1
Description: Mean composition of the metal is 8.8% Ni, 9.6ppm Ga, 42.8% Ge, 2.2% Ir. From Catalogue of Meteorites (2000).
Discovered in 1861 in the Atacama Desert, Chile, and classified as a mesosiderite, Vaca Muerta (Dead Cow in Spanish) is a differentiated silicate and metal rich meteorite containing many silicate and eucrite inclusions
For this meteorite to show such a varied and disrupted character, the Vaca Muerta parent body must have been impacted countless times by different types of material to break up, mix, and fuse the various constituent pieces as displayed in the image below.
The metal inclusion of iron-nickel alloy in the mesosiderites,
exhibits the same properties as octahedrites
(from Mike Reynolds, 2001 Falling Stars pg 77). All the
Vaca Muerta metallic inclusions show areas with finest Widmanstatten
pattern of 0.1mm width band, being the rarest pattern inside of
the octahedrites groups.
The History
Vaca Muerta was found in 1861 by a mining entrepreneur, who correctly identified it as celestial in origin. Later visitors to the area concluded that the heavy, metallic pieces were silver or silver ore, (native iron is extremely rare) and they are known to have removed large quantities (probably more than 2000 kg) to the mining town Copiapo.
About 20 fall-sites had been molested by miners, the rest were virgin. The precise location was unknown for about 100 years, until rediscovered by Edmundo Martinez, in 1985.
In 1988, Holger Pedersen, Claudio Canut de Bon Senior, Claudio Canut de Bon Junior and Harri Lindgren searched the strewnfield, originally found in 1861.
The area, 11.5 km long, 2.1 km wide, is located about 60 km southeast of Taltal, Chile, in the Atacama Desert. It has yielded 80 meteorites with a total mass exceeding 3782 kg. Most fragments were found in an undisturbed state, but some had been broken by prospectors.
The present studies, in connection with historical records, indicate that the original mass of Vaca Muerta exceeded 6 metric tons. One impact feature, somewhat modified by man, consists of a 10.5-m diameter, 1.7-m deep hole, without an uplifted rim. Small masses were scattered up to 85 m from the hole.
The Pedersen search party spent about 100 man-days in the desert, searching for fragments, and excavating them with great care. They recovered the large fragment No. 13, of which the main body, 46 kg, is on display at La Serena Mineralogical Museum, Chile.
From reports, the strewnfield is now picked clean.
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