A pink stone found in the Sahara provides new evidence of the presence of water on Mars more than four billion years ago.
In 2022, a meteorite weighing about 800 g was discovered in Mali, in a desert region. Named Teghaza 001, it does not resemble the most common Martian rocks. Its pink color and crystals attracted scientists' attention. But its real significance lies in its history.
Called Teghaza 001, this pink-colored rock is one of the oldest Martian meteorites ever found on Earth.
Credit: © Darryl Pitt / Maine Mineral and Gem Museum
Researchers first confirmed that it came from Mars. To do so, they studied the composition of its minerals and the different forms of oxygen they contain. These characteristics match those of other Martian meteorites, whose origin was established through analyses carried out on the planet.
The team then sought to determine the age of this rock. It contains tiny zircon crystals, which can preserve a record of when they formed. Analysis of these crystals revealed an age of more than 4.1 billion years. This part of the Martian crust therefore already existed at that time.
That is almost as old as Mars itself, which formed about 4.5 billion years ago. At that time, the planet was very different from the one we observe today. Its surface experienced significant volcanic activity, and water could flow through certain regions.
Teghaza 001 tells the story of this wet past. The rock formed when magma cooled, before being altered by water. Analyses indicate that this interaction occurred around 4.1 billion years ago. The water left chemical changes that researchers can still measure today.
Another distinctive feature is that the meteorite's minerals resemble those detected from orbit in the ancient southern highlands of Mars. Scientists have identified several regions that could correspond to it. However, they cannot determine the exact place from which it originated.
The stone was then blasted off Mars by an impact, probably from an asteroid. The fragment traveled through space before falling to Earth.
These results show that water altered very ancient rocks. This happened long before Mars became the cold, dry world we know today. Further analyses will help clarify how long this water circulated and under what conditions.