Desert meteorite hunters recovered a rose-colored stone weighing nearly two pounds in the Sahara Desert in Mali in 2022. Its age and exact origins remained entirely unknown to finders. This particular find—totaling eight stones weighing just under 800 grams—entered the meteorite trade before being acquired by a private collector. The collector forwarded a fragment to the University of New Mexico. Planetary scientists Carl Agee and Karen Ziegler measured its oxygen isotopes, which serve as geochemical fingerprints for planetary bodies according to NASA.
Discovering Teghaza 001 in Mali
The oxygen isotope values matched those recorded in other Martian meteorites. Initially, the rock was classified as a shergottite, which is the most common and typically younger class of meteorite originating from the Red Planet. Agee noticed distinct anomalies. These included an internal mineral alteration that appeared in reverse compared to terrestrial weathering, unusual oxygen isotope values, and manganese-rich material. Agee then contacted Yang Liu, an expert in planetary samples at NASA‘s Jet Propulsion Laboratory in Southern California.
When I got to the sample, I looked around, I said, ‘That’s boring,’
Liu recalled. She noted that while the high-manganese material turned out to be terrestrial, she quickly recognized the sample as exceptionally unique, as reported by Ars Technica. The meteorite was officially named Teghaza 001 after the salt plain in Mali where it was discovered.
Dating the Ancient Martian Crust
Subsequent age-dating of its minerals revealed that the 800-gram rock formed more than 4.1 billion years ago. This places it among roughly 435 known Martian meteorites and establishes it as one of the three most ancient Martian meteorites ever identified on Earth. Francis Tissot, a geochemistry professor at Caltech, assisted researchers in applying an age-dating method on a piece smaller than a fingernail, allowing scientists to analyze single mineral grains. The findings were detailed in a study published in the journal Science.
It was only after we started looking closely that we realized this meteorite is really unique,
Liu stated, adding that a paper reviewer dubbed the specimen a Rosetta Stone for Mars. Unlike other ancient Martian meteorites that offer narrower glimpses into planetary history, Teghaza 001 is composed mostly of feldspar with mixed darker pyroxene crystals resembling rocks exposed in lunar highlands. The relatively large crystals, measuring up to a millimeter across, indicate the rock cooled slowly at a rate of roughly 0.01 degrees Celsius per year from magma that solidified inside the crust rather than erupting.
Water Interactions on Mars
Data from the analysis indicated that the rock was altered by Martian water approximately 4.1 billion years ago, suggesting the planet may have hosted a more dynamic water cycle than previously understood. Lee Saper, a co-author of the research at NASA’s Ames Research Center, noted that the meteorite records interactions of water and rock alongside possible imprints of the Martian atmosphere as it lost water. A separate study published in Science Advances in June examined the rock’s water content to evaluate how moisture shaped early Martian topography.
By comparing the meteorite’s mineral composition and chemistry with observations from the Mars Reconnaissance Orbiter, researchers matched its mineralogy to the cratered southern highlands of Mars. Like other Martian meteorites, Teghaza 001 was blasted into space by a powerful surface impact before traveling to Earth. Can scientists pinpoint the exact impact site on Mars?
Earlier coverage: Teghaza 001 revealed as rare 4.1-billion-year-old Martian meteorite
