A Martian meteorite fragment containing unexpected grains of mineral could hold clues to the Red Planet’s geological history, according to an international team of researchers.
Prior to the team’s new paper, which was published in Geochemical Perspectives Letters, the red mineral garnet had never been observed in any martian rock sample. Now, the meteorite discovery provides scientists with new clues to Mars‘ extreme past conditions, over its 4.5 billion-year history, which could include hidden magma sources or ancient impact events.
Garnet and Geology
Although the gemstone garnet can come in many colors, it is best known for its dark red varieties, which were historically popular in ancient Egypt, Rome, and Victorian England. Beyond its beauty, the rock is important for the record it keeps of its birth, providing Earth’s geologists with information on our planet’s tectonic forces, ore-forming processes, and the fluid-rock interactions of the crust and mantle.
Similarly, the small grains of garnet discovered in the meteorite sample contain important data for reconstructing the forces that forged the Red Planet long ago.
“The findings add a striking new dimension to our understanding of the geology of Mars and open an exciting new window into the evolution of our planetary neighbour,” said co-author Professor James Darling.
“This discovery is going to expand our knowledge of the geologic processes that are possible on this planet,” said lead author Tanya Kizovski, Assistant Professor of Earth Sciences, from Brock University in Canada. “This new garnet-bearing rock type could give us clues to how Mars has changed throughout its history and new insights into the ancient environments that could have formed the garnet and related minerals.”
Mars Meteorite NWA 8171
The garnet fragments were discovered in a tiny Martian meteorite sample held in the Royal Ontario Museum’s collection, designated NWA 8171, discovered in northwest Africa. Kizovski led the team in analyzing the sample’s mineral and chemical composition after identifying it as a unique piece within the collection.
“This little section of the meteorite looked really interesting, and the chemistry was a bit odd,” Kizovski said. “At first, we assumed it was a mineral called pyroxene, which is very common, but then we decided to take a second look.”
The international effort brought in researchers from Italy’s University di Trieste and the UK’s Open University, utilizing the Royal Ontario Museum’s laser equipment and the University of Portsmouth’s Electron Microscopy and Microanalysis Unit.
Having never been observed in any previous Martian sample, the researchers were surprised to identify garnet in the meteorite’s composition. From their analysis of the sample’s chemistry and mineralogy, the researchers began to consider how the unexpected garnet could have formed.
“Garnet is a classic example of a mineral often found in metamorphic rocks on Earth,” Kizovski said. “The process of metamorphism transforms igneous or sedimentary rocks into a new form through exposure to extreme heat, high pressure, or hot fluids.”
“On Mars, the heat and pressure needed to produce garnet through metamorphism could have come from the impact of a meteorite hitting the surface of Mars, magma rising up into the Martian crust, or both,” Kizovski continued.
Explaining Martian Garnet
While garnet provided geologists with some data about how it formed, this is not like the point of origin stamped on a manufactured good. It is possible that the garnet was deposited on Mars during an earlier meteorite impact, only to later travel through the solar system again, or that it was created by a heretofore unknown magma source on Mars.
Only further analysis of the garnet’s isotopic signatures will allow the researchers to determine whether the mineral formed on Mars or elsewhere. Unfortunately, to do so, the team would have to destroy a portion of this rare and precious sample, which measures only 0.8 by 0.5 millimeters to begin with.
“Measuring oxygen isotopes from the garnet-bearing rock type itself would help to confirm if it is Martian in origin or from an exotic meteorite impactor,” Kizovski said.
“Isotopes are a collection of atoms with equal numbers of protons and electrons, but different numbers of neutrons,” she added, “which was avoided thus far due to its rarity, as it may be the only garnet-bearing Martian rock we have for study.”
A few members of the team are continuing their study of the sample by comparing their findings to Martian data collected by rovers and orbital platforms. Further insights, they hope, may help them discover more about how the garnet could have formed, and what its presence means for the deeper history of the Red Planet.
The paper, “Expanding Mars’ Lithologic Diversity: Discovery of a Garnet-Bearing Clast in NWA 8171,” appeared in Geochemical Perspectives Letters on June 16, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.