The Martian meteorite Northwest Africa (NWA) 16254 is a 406-g gabbroic shergottite found two years ago in Algeria.
Image of the entire NWA 16254 sample studied by Chen et al.: (a) a backscattered electron (BSE) image obtained by the TESCAN Integrated Mineral Analyzer (TIMA); (b) mineralogical mapping via TIMA; (c) distribution map of the iron content obtained via TIMA; (d) distribution map of the calcium content obtained via TIMA. Image credit: Chen et al., doi: 10.15302/planet.2025.25002.
“Martian meteorites represent the only direct samples available in laboratory for studying the composition and evolution of the Martian mantle, as most are igneous in origin and retain geochemical fingerprints of mantle processes,” said lead author Dr. Jun-Feng Chen and colleagues at the Chengdu University of Technology.
“Among these available samples, shergottites, comprising approximately 90% of the Martian meteorite collection, are particularly critical for deciphering mantle dynamics, crust-mantle interactions, and magmatic differentiation on Mars.”
“Shergottites are classified into four petrological subtypes depending on their distinct textural and mineralogical characteristics: including basaltic, olivine-phyric, poikilitic, and gabbroic.”
“These variations reflect distinct formation environments, ranging from shallow subsurface crystallization to potential surface eruptions, with gabbroic shergottites notably preserving coarse-grained textures indicative of slow cooling in crustal magma chambers.”
In the new study, the authors combined advanced mineralogical mapping and geochemical analyses to decode the history of NWA 16254.
They revealed decoupled geochemical behaviors in pyroxene cores and rims, a phenomenon critical for reconstructing magma chamber dynamics.
“Our study reveals that NWA 16254 formed initially under high-pressure conditions (4.3-9.3 kbar) at the Martian mantle-crust boundary, where magnesium-rich pyroxene cores crystallized,” the researchers said.
“Later, the magma ascended to shallow crustal depths (<4 kbar), where iron-enriched pyroxene rims and plagioclase developed.”
“This prolonged cooling process, preserved in the meteorite’s coarse-grained texture, suggests episodic melt extraction from a long-lived, depleted mantle reservoir — a critical clue for reconstructing Mars’ magmatic evolution.”
“The meteorite’s geochemical depletion, marked by light rare earth element depleted and low oxygen fugacity, aligns it with a meteorite called QUE 94201, hinting at a shared magma source.”
“Its gabbroic texture, indicative of slow cooling in crustal chambers, distinguishes it as a unique archive of subsurface magmatism.”
“These findings challenge existing models of Martian volcanic evolution, as NWA 16254’s consistently low oxygen fugacity, corroborated by Ti3+-bearing ilmenite assemblages, implies sustained reducing conditions during crystallization.”
“This underscores the heterogeneity of Mars’ mantle and raises questions about the planet’s redox evolution over billions of years.”
“Future geochronological studies could resolve whether this meteorite represents ancient mantle melting (2.4 billion years ago) or younger magmatic activity, offering clues to Mars’ thermal history.”
The team’s paper was published May 13, 2025 in the journal Planet.
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Jun-Feng Chen et al. Petrography and geochemistry of a newly discovered Martian gabbroic shergottite NWA 16254. Planet, published online May 13, 2025; doi: 10.15302/planet.2025.25002