A Complete Slice of the Tissint Martian Meteorite Fall

On 18 July 2011 a bright fireball exploded into many pieces over the Oued Drâa valley in Morocco, site of the country’s longest river. It was the most recent of only five observed falls of Martian meteorites. The determination of Martian origin is the result of research by scientists throughout the world. In addition to the more arcane markers in common, most Martian meteorites exhibit an unusually young crystalline age (indicating that they cannot be from asteroids, which all cooled about 4½ billion years ago). Many Martian meteorites also contain water-bearing minerals, consistent with the evidence for water on Mars. The smoking gun of Martian origin appeared in 1995 when minute amounts of gas found in tiny glassy inclusions of two suspected Martian meteorites were analyzed—and it was found to match perfectly with the signature of the Martian atmosphere as reported by NASA’s Viking missions. As is the case with lunar meteorites, the delivery mechanism is believed to be an asteroid impact that jettisoned material off the Martian surface and into an Earth-intersecting orbit. Like many other Martian meteorites, this specimen probably formed as a basalt flow at or near the surface of Mars. The grains of feldspar (a calcium-aluminum silicate mineral) in the rock were transformed into glass, a mark of the intense shock pressure experienced by the rock when it was blasted off the surface of Mars by an enormously energetic impact event. The meteorite is traversed by thin veins of black glass which also attest to the extreme shock experienced by the specimen.

Christie's would like to thank Dr. Alan E. Rubin at the Institute of Geophysics and Planetary Physics, University of California, Los Angeles for his assistance in preparing this catalogue note.