A rosy stone found in the Sahara Desert in 2022 has been identified as a Martian meteorite formed at least 4.1 billion years ago. Known as Teghaza 001, the nearly two-pound rock is one of the oldest samples of Mars ever found and could help scientists reconstruct the planet’s early history.

The findings, published October 29 in Science, are based on analyses of zircon crystals containing uranium, along with measurements of rubidium and strontium isotopes. Both methods produced similar age estimates.

Scientists have identified more than 400 Martian meteorites. These rocks were blasted from Mars by impacts, traveled through space and eventually reached Earth. Before Teghaza 001, only two meteorites offered comparable insight into the young planet: Allan Hills 84001, dated to about 4.1 billion years ago, and Northwest Africa 7034, which contains fragments more than 4.3 billion years old.

Teghaza 001 is also notable for its composition. Its volcanic minerals indicate that the rock began as magma, cooled into part of Mars’ crust and was later altered by underground water. That evidence adds to research suggesting that Mars, now cold and dry, was considerably wetter in its distant past.

The meteorite’s chemistry may point to Mars’ Noachian southern highlands. Its composition matches observations made by NASA’s Mars Reconnaissance Orbiter, and researchers have identified 13 possible locations that could correspond to its origin.

The presence of evidence for ancient water is relevant to the question of whether Mars once supported life. Water is necessary for all known organisms, and the study’s researchers say the findings support the idea that early Mars had some of the ingredients and conditions required for habitability. They do not, however, provide direct evidence that life existed there.

Researchers caution that Teghaza 001 cannot answer every question about Mars’ evolution. Because its exact source location remains unknown, scientists say returned samples collected directly from the planet will be needed for a fuller understanding of its geological history.

Sources: Smithsonian Magazine.