Tegaza 001, a meteorite found in Mali’s Sahara desert four years ago, may be a fragment of Mars’ primitive crust formed at least 4.1 billion years ago. The meteorite is an unusually well-preserved sample of a single type of ancient igneous rock, according to a new paper published in Science.
The study suggests that Tegaza 001 formed early in Mars’ geological history and later interacted with water or other hot, mineral-rich fluids. The researchers identified the northwestern region of the Hellas impact basin in Mars’ southern highlands as its most likely source.
The largest fragment of the Martian meteorite Tegaza 001. Image credit: Liu et al., doi: 10.1126/science.adz5646.
An unusually ancient Martian rock
Tegaza 001 consists of eight pieces with a combined mass of 798.5 grams. The largest fragment weighs 442 grams and is approximately 10 centimeters in diameter.
“It wasn’t until we started looking at it carefully that we realized that this meteorite was truly unique,” said Dr. Yang Liu, a researcher at NASA’s Jet Propulsion Laboratory.
“One of the paper’s reviewers called it the Rosetta Stone of Mars.”
Nearly all of the approximately 300 known Martian meteorites are much younger than the planet’s surface, which is dominated by terrain more than 3 billion years old.
The three major groups known as shergottites, nakhlites and chassignites formed after 2.4 billion years ago. Only two older examples had previously been identified. Allan Hills 84001 is a crystallized rock approximately 4.1 billion years old, while the other is a group of debris-filled rocks that includes Northwest Africa 7034, some of which are more than 4.3 billion years old.
According to the study authors, Tegaza 001 differs from both. It is a coarse-grained, plagioclase-rich igneous rock called gabbro. Its internal structure indicates that it probably cooled slowly underground.
Dating the meteorite
The researchers dated zircon crystals in the meteorite using the uranium-lead method and estimated their age at approximately 4.11 billion years.
A separate rubidium-strontium analysis produced a less precise but consistent age of about 4.24 billion years. That measurement may record a period when hot, mineral-rich water was circulating through the rock—not when the rock originally solidified, but shortly after it crystallized.
In either case, Tegaza 001 formed during the earliest part of Mars’ geological history, no later than about 4.1 billion years ago.
Dr. Carl Agee, director and curator of the Meteorite Research Institute at the University of New Mexico, said: “There are parts of Black Beauty that are of that age, but the meteorite as a whole is a collection of many different types of rocks.”
“This was a big surprise because Tegaza 001 is just one type of pure rock and is more than 4.1 billion years old.”
“This is the oldest igneous rock ever discovered, and in addition, its composition appears to contain clues that suggest it was in an environment with flowing liquids or water.”
Evidence of water on early Mars
Tegaza 001 also contains evidence of interaction with water or other fluids. Its oxygen isotopes are heavier than those found in other Martian meteorites. The researchers believe this may result from interaction with oxygen-18-rich fluids in the crust or directly with magma.
The minerals in the rock underwent chemical changes on Mars long before the meteorite was ejected into space.
By comparing the meteorite’s chemistry with orbital measurements of Mars, the scientists identified the southern highlands—specifically the northwestern region of the Hellas impact basin—as the most likely source area.
“This is not very common, so not only is it ancient and samples a different type of environment from a different era on Mars, but there are no other samples like it,” Agee said.
“The chances of getting something like this again anytime soon are very low to almost impossible.”
Yang Liu et al., “Mars’ early crust and mantle have been collected from meteorites that formed about 4.1 billion years ago,” Science, published online October 29, 2026. doi: 10.1126/science.adz5646.
Source: www.sci.news
