This complete slice of NWA 7944 is from an 815-gram Martian meteorite that was analyzed after being recovered from an area designated as the North West African grid of the Sahara Desert. Because there are few geographic features and a lot of meteorites in this region, samples from this area are numbered sequentially. NWA 7944 most likely originated about 180 million years ago as a basalt flow that intruded layers of pre-existing rocks in the upper crust of Mars. NWA 7944 cooled fairly quickly, producing a medium-to-fine-grained igneous texture. The Martian origin of the rock is in part inferred (with high confidence) by its chemical and isotopic similarity to a particular Antarctic meteorite named Elephant Moraine A79001 that contains gas bubbles identical in composition to the Martian atmosphere. The latter measurement was made at the Martian surface by NASA’s Viking spacecraft lander in 1976. A major collision blasted NWA 7944 off the surface of Mars with such force that the rock’s feldspar grains (a calcium-aluminum silicate mineral) were transformed into glass.

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