Meteorite found in the Sahara is a piece of Mars at least 4.1 billion years old

A rose-colored rock picked up in the Sahara Desert in 2022 is a piece of Mars that formed at least 4.1 billion years ago, scientists reported on October 29, 2026, in the journal Science. It is named Teghaza 001 after a salt plain in Mali, its discovery site, and weighs nearly 800 grams (about 2 pounds). NASA, which funded the research, says it is one of the three oldest of the roughly 435 Martian meteorites known on Earth.

That age makes it unusual. Most meteorites from Mars are geologically young and do not represent the planet's surface, which is dominated by ancient rock, the authors write. Teghaza 001 is an igneous rock that cooled slowly, and its composition, minerals and texture set it apart from other Martian meteorites. The team concludes that it is a fragment of early crust whose source in the mantle was chemically distinct and primordial in composition.

“This is really our first piece of Martian crust from a part of Mars we’ve never had a sample of before,” said Lee Saper, the paper's second author, who did the research as a postdoctoral scholar at NASA's Jet Propulsion Laboratory (JPL) and now works at NASA's Ames Research Center.

Dating single grains

Scientists at the University of New Mexico first identified the rock as Martian by matching its oxygen isotopes to those of other Martian meteorites, and it looked like a shergottite, the most common class of meteorite from Mars. When the lead author, Yang Liu of JPL, examined it, she noticed strange textures and minerals that were new to her. She and her colleagues also found zircon crystals, which geologists can use to date a rock precisely. “One of the paper’s reviewers called it a Rosetta Stone for Mars,” Liu said.

Co-author François Tissot of the California Institute of Technology (Caltech) helped the team use an in-situ rubidium-strontium method developed by his group. Instead of dissolving a whole sample, it dates single mineral grains on the surface of a fragment smaller than a fingernail. According to NASA, the technique is fast and precise and leaves rare material available for later studies. The dates showed that water had altered the rock around 4.1 billion years ago, suggesting that it formed even earlier.

How it compares

The other two meteorites in that oldest group each give a narrower view of Mars' history, NASA says. ALH84001, found in Antarctica in December 1984, is similar in age but is made almost entirely of one mineral. Northwest Africa 7034, known as Black Beauty, is about 2.1 billion years old and is made of small fragments of volcanic rock. Teghaza 001 instead holds a mix of igneous minerals that records how crust formed from cooling magma and was later changed by water underground.

Where on Mars it came from

The rock's minerals match those NASA's Mars Reconnaissance Orbiter has seen in the cratered highlands of Mars' southern hemisphere. Using the orbiter's data, the researchers identified 13 places on the planet with similar mineralogy and chemistry, though NASA notes that nobody can know for sure where a Martian meteorite came from. Like the others, Teghaza 001 was thrown off the surface by an impact before it eventually reached Earth.

Clues to early water

Minerals altered by water, together with oxygen isotope measurements, indicate that the rock reacted with fluids rich in the heavy isotope oxygen-18 before an impact launched it into space, the Science paper says. A separate study of the same meteorite, published on June 12, 2026, in Science Advances, measured water and the ratio of deuterium to hydrogen in its phosphate minerals. It set a lower limit on that ratio for Mars' water 4.1 billion years ago of roughly twice the value in Earth's seawater. The authors say this supports models in which hydrogen escaped quickly to space from the young planet's atmosphere.

Liu and her co-authors hope other researchers will now study the meteorite. “We’ve only scratched the surface,” Liu said.