Teghaza 001 was acquired through the desert meteorite trade, where hunters comb the Sahara for dark stones that stand out against the sand. Its eight stones, weighing just under 800 grams in total, were bought by a private collector, who sent a piece to the University of New Mexico for classification. There, planetary scientists Carl Agee and Karen Ziegler measured its oxygen isotopes. “Each planetary body has a very characteristic oxygen isotope value,” Liu says. Teghaza 001’s values matched those of other Martian meteorites.
At first, the rock was classified as a shergottite, the most common (and young) type of Martian meteorite. But Agee noticed some oddities and reached out to Liu. One of Teghaza’s minerals had been altered on the inside while its outer part stayed pristine, the reverse of how weathering on Earth works. The oxygen isotopes looked a bit strange, and there was some manganese-rich material similar to what Liu had studied in Black Beauty.
“When I got to the sample, I looked around, I said, ‘That’s boring,’” Liu said. “The high-manganese material is actually terrestrial, but I quickly realized the sample is very different, very special.”
Teghaza 001 is made mostly of feldspar, a pale mineral common in the crusts of rocky planets. It has darker pyroxene crystals mixed in; according to Liu, those resemble some rocks exposed in the lunar highlands. Its crystals are rather big, up to a millimeter across, which scientists interpret as an indication it cooled down slowly. “For slow-cooled rock, they tend to have time to grow bigger,” Liu said.
By comparing the crystals with lab experiments and terrestrial rocks, the team estimated Teghaza 001 cooled by roughly 0.01° Celsius per year, indicating it formed from magma that never erupted but instead solidified inside the crust.
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