In 2022 a group of nomadic meteorite hunters discovered a strange stone in the Sahara Desert. Called Teghaza 001, initial analysis by experts showed it was a meteorite from Mars. Now new research reveals it’s the oldest ever found, and it’s revealing more about the Red Planet’s complex history.
Scientists fortunate enough to get their hands on samples of the space rock have been analyzing tiny pieces of Teghaza for years to better understand exactly what it is and when it formed. The new paper, published today in Science, identifies it as a piece of Mars’s crust that’s at least 4.1 billion years old, from a time when that world was warmer, wetter and more Earth-like.
“We’re holding a piece of a rock that’s dated even before the oldest Earth rock—a piece of Mars that’s so ancient, it existed when life had just started on Earth,” says Yang Liu, lead author of the study and a planetary scientist at the Jet Propulsion Laboratory at the California Institute of Technology.
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Several hundred Martian meteorites are known. All of them got here by giant impacts that have pelted Mars for eons, occasionally blasting bits of the planet into space, some of which by chance fall to Earth. Most are relatively young, each revealing little more than a snapshot from the most recent 600 million years or so of Mars’s 4.5-billion-year history. The only other known intact ancient sample, a meteorite discovered in Antarctica in the 1980s, is just 10 million years younger than Teghaza.
When Liu received a piece of the rock from the team at the University of New Mexico that initially analyzed it, she was tasked with studying its manganese, an element that can help scientists discern whether an ancient rock was ever exposed to water and oxidation. But soon she noticed the presence of zircons in the meteorite—tough crystalline minerals that can endure in rock for billions of years and contain radioactive isotopes that can be used for ultraprecise dating. The zircons, Liu realized, made Teghaza very special. In the exhaustive work that followed, she and her team isolated zircons and other minerals from small scraps of their precious samples, pinning down the meteorite’s chemical composition and dating its elements to the early days of Mars’s history.
Darryl Pitt
Teghaza, they found, is an igneous rock that formed from slowly-cooled magma and was once a piece of the planet’s crust. Comparing ratios of certain elements in the meteorite to those measured by orbiters for larger swaths of the planet’s surface, Liu and her team found the closest matches within the rugged, crater-pocked terrain in Mars’s southern highlands, a region thought to be among the world’s most ancient.
Pinpointing the possible sites where Teghaza was launched by a giant impact on its fateful journey to Earth is a feat all its own, but the meteorite’s chemical composition shows something even more enlightening.
As detailed in work from Liu’s team published earlier this year, some of the minerals in the meteorite have been aqueously altered—a sign that liquid water once percolated through Mars’s ancient mantle and crust. And careful analysis of remnant hydrogen trapped inside Teghaza shows that even when the rock formed, more than 4.1 billion years ago, the planet was already well on its way to losing most of its atmosphere, growing cold and transitioning to its current freeze-dried state. Taken together with the results in today’s paper, Liu says, all this reinforces how Mars’s mantle is likely more heterogeneous and complex than many planetary scientists have long assumed.
Liu’s research on Teghaza is ongoing; her team “has only scratched the surface,” she says, of the insights the meteorite might hold.
A clearer understanding of Mars’s deep past can also inform our own. Mars and Earth formed in similar ways, with giant magma oceans that cooled into cores, mantles and crusts. Because of its tectonic activity that continuously buries, melts and recycles the planet’s crust across geological time, Earth’s surface does not preserve many (if any) samples from its primordial youth—but Mars is different, as its geophysical tumults ebbed long ago.
One reviewer of the paper called this meteorite “the Rosetta stone of Mars,” Liu says, because it may be able to tell the stories of planets across the solar system.
“We’re hoping to start using Mars to compare and contrast and to understand what makes a planet habitable for life,” she adds.
There’s much still to learn about this meteorite’s mysteries, says Anya Udry, a planetary scientist at the University of Nevada, Las Vegas, who was not involved with the Science study. But truly understanding the full story of Mars requires more than gathering additional impact-imported fragments of the Red Planet here on Earth; what’s necessary is more visits to the world itself.
“Mars is a complex planet, and this meteorite is really cool, but we don’t know exactly where it came from, so this is really another example of why we need to bring back samples,” she says.
