Northwest Africa 2737 (NWA 2737)
Photo © Bruno Fectay & Carine Bidaut JPEG (221K) Total known weight: 611 grams	Photo © Bruno Fectay & Carine Bidaut JPEG (266K) One of the NWA 2737 fragments

This group is named for its first member, Chassigny, a meteorite that fell in France in 1815. As a witnessed fall that was recovered in the early days of meteoritics, it was one of the first meteorites to be recognized as a genuine rock from space, and it subsequently proved to be one of the most intriguing ones. Chassigny is a cumulate rock, resembling a terrestrial dunite. It consists of about 91% iron-rich olivine, 5% clinopyroxene, 1.7% plagioclase, 1.4% chromite, 0.3% melt inclusions, and other accessory minerals and phases. The melt inclusions contain rare amphiboles, and cracks within Chassigny are filled with carbonate and sulfate salts, indicating a mild pre-terrestrial aqueous alteration.

Photo © Bruno Fectay & Carine Bidaut JPEG (1.2 MB) The NWA 2737 fragments.	Photo © Bruno Fectay & Carine Bidaut JPEG (1.7 MB) Carine Bidaut & Bruno Fectay

Chassigny displays a rather typical oxygen isotopic composition, placing it clearly within the SNC field. Its crystallization age of 1.36 billion years and its compositional and elemental trends, indicate a close relationship exists between Chassigny and the nakhlites, and suggests an origin from the same parent magma on Mars. However, Chassigny contains noble gas values that are entirely different from those found in other SNC members or in the Martian atmosphere. It is suspected that these gases might originate from the Martian mantle, suggesting a formation for Chassigny within a magma pluton deep inside the Martian crust.

Four years ago, we brought from Morocco, a black rock, broken in several pieces. This rock was not recognized immediately as a meteorite so we file it with hundreds of other meteorwrongs. It is only last summer, that a fragment was entrusted to scientists and that the true nature of the sample was recognized. Called "Diderot" by the scientists in homage to the 18th century encyclopedist of Langres in France, this meteorite bears today the name of Northwest Africa 2737 (NWA 2737) according to the international nomenclature.

Among the 25000 meteorites known to date, only 33 were torn off on the surface of Mars by violent impacts. These specimens count by the rarest matters on Earth. No other Chassignite have ever been discovered since Chassigny fall in 1815, with NWA 2737, a huge lack have been filled. The total of our unpaired SNC is now 7.

With 611 gr TKW, it is very close to Chassigny known mass. Scientists found that unlike Chassigny, NWA 2737 have been hardly shocked, the pressure was so high that it turned the olivine into black. such a deformation in olivine have never been observed before.

Photo © Bruno Fectay & Carine Bidaut JPEG (801K)	Photo © Bruno Fectay & Carine Bidaut JPEG (900K) Closeup of a slice of NWA 2737. Note the blue high pressure glass.

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