Scientists have identified one of the oldest Martian rocks ever found on Earth — and it’s revealing new clues about the red planet’s earliest history, including evidence that water altered its crust at least 4.1 billion years ago. The rose-coloured meteorite, known as Teghaza 001, has a unique chemical composition that sets it apart from previously studied samples from Mars, scientists say. “This is a very rare, ancient Martian meteorite, and it gives us a chance to look at the early crust and mantle of Mars, at a time when life was just starting on Earth,” said Yang Liu, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and lead author of a study on the sample published Oct. 29 in the journal Science. This meteorite is believed to have formed from magma derived from the mantle — a planet’s inner layer of hot rock — which later became part of the outer crust. “The chemistry of this sample shows it comes from a Martian crustal area we have not sampled before,” Liu added. Teghaza 001 is named after a salt plain in the West African country of Mali, where meteorite hunters discovered it in 2022. The meteorite consists of eight fragments weighing 798.5 grams (1.76 pounds) in total, with the largest weighing 442 grams (0.97 pounds). The impact of an asteroid or comet that struck Mars blasted Teghaza 001 out of the red planet’s relatively weak gravity and into space. The meteoroid then started orbiting the sun, potentially for several million years before being captured by Earth’s gravity and entering our planet’s atmosphere. It’s hard to determine when the impact on Mars originally occurred, or even when the meteorite landed on Earth, but the sample’s surface features reveal that it might have spent some time in the desert before its discovery, according to Liu. “It is always nice to see a new visitor from Mars, and this one is ancient — one of the oldest from the planet, and older than any home-grown Earth rock,” said Matthew Genge, an associate professor of Earth and planetary science at Imperial College London, who was not involved with the study. “That alone is fascinating,” Genge said in an email. “It gives a window into the earliest stages of Mars history, a time when water is expected to have been present on the planet.” A lucky gamble An initial analysis didn’t immediately reveal that the rock was particularly old, and Liu almost passed on studying it. “When I was first offered it,” she said, “the sample was classified as a shergottite, the most abundant type of Martian meteorite we have on Earth.” Liu had previously analyzed several shergottites, which make up almost 90 per cent of the known Martian meteorite collection and are usually less than 600 million years old, but she ultimately agreed to investigate the sample. She noticed Teghaza 001 contained zircon, a type of crystal that forms when molten rock cools. “Zircons are like a time capsule that allows us to precisely date the formation age of a rock,” she said. Dating of the crystals indicated an age of at least 4.1 billion years, which means the meteorite formed roughly within the first 400 million years of Mars’s existence. To confirm this estimate, the sample was also processed via a new aging method developed by study coauthor Hayward Melton, a doctoral student at the California Institute of Technology. “This method uses a laser to vaporize very small regions of a sample, instead of dissolving larger pieces of it,” Melton said in an email. “Using laser means that we can measure samples like Teghaza 001 significantly faster than traditional techniques.” The team used a small laser beam — about one-tenth the diameter of a human hair — to analyze the tiny grains and crystals inside of the samples. This new technique reduced the time required to date a sample from a month to a day, Melton added, and left more of the original material available for further studies. The meteorite is a basalt, similar to rocks that cover the floor of Earth’s oceans and erupt from volcanoes in places such as Iceland and Hawaii, according to Genge. Teghaza 001 has a unique composition that indicates it interacted with water in the ancient Martian crust, the new analysis has shown. This may give scientists “a deeper understanding of not only early Mars, but also Earth, and help us learn why Mars became dry while the Earth did not,” Melton said. “This, in turn, would have implications for understanding the habitability of planets.” Other peculiar features make Teghaza 001 stand out from Martian meteorites. It’s made mostly of two calcium-rich minerals, but in proportions that have never been seen before in any other samples, Liu said. The specimen also contains isotopes of oxygen in relative abundance that is unlike other known rocks from the red planet, according to Liu. The mineral and chemical composition of a meteorite can help scientists ascertain its Martian origin by comparing it with data gathered on the planet’s surface by NASA missions to Mars, including the Viking landers and the Curiosity and Perseverance rovers. For Teghaza 001, the researchers went one step further and identified 13 locations on Mars’ southern highlands from where the rock could have originated. “I think the science community will be very interested in this sample, and there will be many more discoveries to come,” Liu said. “I am still very interested in resolving some questions I couldn’t answer with our paper, which is only in the beginning.” ‘A possible feast of discovery’ After its discovery in 2022, the meteorite caught the attention of Darryl Pitt, a meteorite collector and chair of the meteorite division at the Maine Mineral & Gem Museum in Bethel, Maine. “What drew me most to Teghaza 001 was a mineralogy that was unlike that of any previously studied Martian sample, combined with its age,” Pitt said. “This set the table for a possible feast of discovery.” He eventually brokered a deal for the museum to acquire the rock for an undisclosed amount. “What is truly remarkable about Teghaza 001 is that it allows us not only to be able to study another planet,” said Genge of Imperial College London, “but also to peer deep under its surface to see what the planet was like only 500 million years after it formed.” By Jacopo Prisco, CNN
