Specimens of the planet Mars are among the most exotic substances on Earth with less than 300 kg (650 lbs) known to exist. The delivery mechanism to Earth was an asteroid impact on Mars that ejected material off the Martian surface into an Earth-crossing orbit. The determination of Martian origin is the result of research conducted by hundreds of scientists throughout the world. In addition to many arcane chemical and isotopic markers, most Martian meteorites possess an unusually young crystalline age and they are far younger than meteorites that originate on asteroids.

Similar to the lot now offered, there was an exotic group of enigmatic meteorites that shared numerous characteristics and formed on a planetary body — but were clearly not from Earth. It was believed they were most likely Martian as the escape velocity required to jettison rocks off the Venusian surface — the next most likely candidate — is much greater than that of Mars. The long-believed link to Mars was speculative until 1983, when it was found that the abundances of noble gases within a melt pocket closely resembled noble gases in the Martian atmosphere measured on the Martian surface by NASA’s Viking landers in 1976. And then in 1995 was the historic scientific study published in Science entitled “Signatures of the Martian Atmosphere in Glass of the Zagami Meteorite”. (See lot 36)

NWA 12690 is the 12,690th distinct meteorite to be recovered and classified by scientists from the North West Africa (NWA) grid of the Sahara Desert. It was found on December 16, 2018 by a Malian nomad near Achemelmel in Northern Mali.

The official classification of NWA 12690 appears in the 108th edition of the journal of record, the Meteoritical Bulletin. The write-up was done by one of the world’s experts in Martian meteorites, Dr. Ansgar Greshake at the Museum für Naturkunde in Berlin, Germany. Dr. Greshake’s work was then vetted by his colleagues on the Nomenclature Committee of the Meteoritical Society prior to being approved and published. A copy of the abstract and write-up accompanies this offering. Weighing 9.085 kilograms (precisely 20 pounds), NWA 12690 is the third largest piece of Mars on Earth. At one time there were two Martian meteorites that were larger, but shortly following their arrival decades ago they were subdivided into much smaller specimens and distributed to museums, research centers and collectors.

NWA 12690 is a volcanic rock predominantly composed of calcic pyroxene crystals (up to 3 mm in size) which evidence complex compositional zoning. There are also similarly sized grains of maskelynite (plagioclase feldspar that underwent an extraordinary shock event and was transformed into glass) suspended throughout the matrix. Other minerals include ilmenite, ulvöspinel, merrillite, and pyrrhotite. The external surface of NWA 12690 has a grey-green cast. Patches of fusion crust — the result of melting during descent through the Earth’s atmosphere — are in evidence. NWA 12690 contains abundant shock melt pockets; the presence of Martian atmosphere can be confidently inferred. This extraordinary offering is accompanied by a custom armature and Lucite dome.

Christie's would like to thank Dr. Alan E. Rubin at the Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles for his assistance in preparing this catalogue.

233 x 244 x 154mm (9 x 9.66 x 6 in.) and 9.085 kg (20 lbs)
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