Oldest Mars Meteorite Found in Sahara Rewrites History

A rose-colored rock is rewriting what scientists know about the Red Planet, and the oldest Mars meteorite is the star of the week. A paper published Thursday in the journal Science describes the rock as a piece of Mars that formed more than four point one billion years ago, according to NASA.

That makes it one of the oldest Martian meteorites ever found on Earth. The nearly two-pound stone was discovered in the Sahara Desert in 2022, and for a while nobody knew how old it was or where it came from. Now researchers say it is a rare time capsule from the earliest chapter of a world that once had water.

A desert find with a Martian past

The meteorite is named after the salt plain in Mali where it was found. It weighs about eight hundred grams, and it is one of roughly four hundred thirty-five meteorites known to have come from Mars. Collectors often find these rocks in deserts or on snowy plains, where they stand out against barren ground.

Researchers at the University of New Mexico first identified it as Martian using its oxygen isotopes, which act like geochemical identifiers for different planetary bodies. It looked like the most common type of Mars meteorite. Lead author Yang Liu of NASA's Jet Propulsion Laboratory nearly passed on studying it, but odd textures caught her eye.

How scientists dated it

The breakthrough came from tiny zircon crystals inside the rock. Zircons record clues about when a rock formed, which lets geologists age-date a sample with precision. Caltech coauthor Francois Tissot helped the team use a new in-situ rubidium-strontium dating method that worked on a piece smaller than a fingernail.

That matters because older methods dissolve the entire sample. Tissot's approach analyzes single mineral grains on the surface and preserves rare rocks for future study. Tissot said his lab is one of very few in the world able to perform this kind of age-dating, and the first to date such an ancient Martian meteorite, according to NASA.

When the results came back, Liu was shocked, according to NASA. The rock had been altered by Martian water around four point one billion years ago, which suggests it formed even earlier.

Why it is called a Rosetta Stone for Mars

Only three Martian meteorites are this ancient. One, found in Antarctica, is made almost entirely of a single mineral. Another, nicknamed Black Beauty, formed about two point one billion years ago. Teghaza stands apart because it carries a mix of igneous minerals that tells a story of crust forming from cooling magma and then being altered by water below the surface.

Liu said one of the paper's reviewers called it a Rosetta Stone for Mars. Her colleague Lee Saper described it as the first piece of Martian crust from a part of Mars never sampled before, according to NASA.

Researchers say the Teghaza meteorite also gives a map clue. The team identified thirteen possible places on Mars that match the meteorite's chemistry and mineralogy, based on observations by NASA's Mars Reconnaissance Orbiter. Nobody can know exactly where it came from, but the shortlist is in the southern highlands.

What this means for the search for ancient water

The clues in the rock's oxygen isotopes, texture, and chemistry point to a much more dynamic water cycle on early Mars. A separate paper published in Science Advances in June looked at the meteorite's water content, and together the studies show how water shaped the young planet.

For anyone who loves space news, it is a reminder that some of the best Mars science does not need a rocket. The Teghaza meteorite proves sometimes the sample just lands in the desert and waits for someone curious enough to look closely. Want more discoveries like this? Browse the science coverage and the world news page.

Liu and her coauthors say this is only the beginning, and they are eager to see what the wider scientific community learns next. Liu summed it up by saying the team has only scratched the surface. The full paper is available through Science.