Sahara meteorite dated to at least 4.1 billion years shows early Mars had water

A rock from young Mars

Teghaza 001 broke into eight pieces after falling in the Sahara, about 34 kilometres from the village of Bir Salí in Mali. It was found in 2022, and a study published in Science on 29 October 2026 places its formation in the Martian crust at least 4.1 billion years ago. The largest of the fragments is roughly the size of a human fist. The rock dates from the period when Earth and Mars were still cooling and forming their outer crusts, after the planets of the Solar System formed about 4.5 billion years ago. Scientists say it may be the oldest piece of Mars they have in hand.

How the age and origin were established

The rock is a gabbro, an igneous rock that forms when magma cools slowly and crystallises. Its main minerals are feldspar and pyroxene, and it also contains zircon crystals that hold uranium. Researchers dated it by measuring how uranium decays into lead over time, and the figure is a minimum rather than an exact date. The Martian origin of meteorites like this one is identified through their oxygen isotope ratio, which works as a geological fingerprint for each body in the Solar System. Of the 435 Martian meteorites found on Earth so far, all were recognised this way. Their origin is confirmed by comparing their mineral and chemical makeup with data from NASA missions, including the Viking spacecraft and the Curiosity and Perseverance rovers.

Evidence of water on early Mars

The chemistry of the gabbro shows it reacted with water while it cooled slowly and crystallised beneath the Martian surface. Analyses indicate that water seeped down from the surface into the crust, much as groundwater moves through Earth's crust today. Hydrogen and oxygen isotope ratios support that conclusion. The water reached deeper than the surface and interacted with materials that came up from the planet's mantle. Scientists have already identified landforms that suggest ancient rivers and lakes, and possibly a large body of water in the northern hemisphere. Yang Liu of NASA's Jet Propulsion Laboratory, which Caltech manages, led the study and described the rock as a witness to a period when Mars was probably warmer and wetter than for most of its history.

From desert find to published study

The meteorite was found in 2022, and the research unfolded in stages over the following years. The team's earlier study in Science Advances, published in June 2026, measured how much water the rock holds and how that water shaped the young planet's surface. The main study on the rock's age and chemistry appeared in Science on 29 October 2026. The sequence is set out in the chart below.

What the discovery does not show

The findings do not prove that life existed on Mars. They offer new evidence that about 4.1 billion years ago, environmental conditions could potentially have supported microbial life. Mars is now a cold, dry desert, while NASA missions have found evidence of lakes, rivers and seas in its distant past. Liu said Martian meteorites are the only samples scientists hold from Mars, a basis for understanding how the planet formed. They also allow researchers to test in a laboratory whether Mars could have supported habitable conditions.