Stony-iron, Mesosiderite – MES-A1 Atacama Desert, Chile (25°45' S, 70°30' W)

Named after a dried riverbed near the meteorite’s impact site just 250 kilometers from the Imilac strewnfield (see previous lot), Vaca Muerta (Spanish for “dead cow”) is a rare mesosiderite with silicate inclusions “welded” together in iron-nickel matrix. Vaca Muerta struck Earth approximately 3500 years ago and was first discovered in the late 1800s by prospectors who thought they had found silver. They were mistaken, and as a result of their exasperation, the locality of the strewnfield had not been documented. It was not until a century later that an enterprising student rediscovered the site; he found several hundred kilos of meteorites left behind by miners who had extracted the metal nodules from their silicate-rich matrix. Some of the silicate nodules in the meteorite have the highest europium-samarium ratio (two rare-earth elements) known in the Solar System. Vaca Muerta’s intriguing heterogeneous composition is the result of the countless collisions that its parent body experienced in the asteroid belt. Mesosiderites are a rare class of stony-iron meteorite consisting of approximately equal parts of metallic iron-nickel and silicate. The silicate component itself consists mainly of the minerals Ca-pyroxene and Ca-rich feldspar and is very similar to some basaltic meteorites from the asteroid Vesta.