"I didn't think a rock like this existed on Earth," a geologist at the Lunar and Planetary Institute in Texas told the Washington Post. It looks like a polished rock, dark brown with a clay-colored stripe — but it's actually one of the oldest Mars meteorites ever found, blasted by an impact from the surface of Mars billions of years ago: Technically speaking it's a collection of eight rock fragments, the largest of which is about the size of a fist. Nearly two pounds of the meteorite was discovered in the Sahara in Mali in 2022, and most is now held by a museum in Maine. Within two years, an initial examination determined the meteorite hailed from Mars; scientists are now finally digging deeper, with stunning results. It offers records of "interactions of water and rock and maybe even an imprint of the Martian atmosphere as it was losing water," says Lee Saper, co-author of a new paper recently published in Science. "It was only after we started looking closely that we realized this meteorite is really unique," said Yang Liu of NASA's Jet Propulsion Laboratory in Southern California, the lead author of a new paper published in Science. "One of the paper's reviewers called it a Rosetta Stone for Mars." Its mix of minerals "tells a story about how the planet's crust formed from cooling magma before it was eventually altered by subsurface water," NASA's JPL says in an announcement. The Washington Post reports: The story begins 4.1 billion years ago, when crystals of a mineral called zircon probably solidified out of molten magma on Mars. "That was a game changer," [said Yang Liu, a planetary scientist at NASA's Jet Propulsion Laboratory in California], since scientists can date zircon very precisely, and it has been rare in other Mars meteorites. The date immediately put the Teghaza meteorite on special footing, alongside only two other Mars rocks known to have formed by 4 billion years ago... Perhaps most intriguingly, the researchers also saw signs that the rock had been exposed to water during its evolution, a find detailed in work published this summer in Science Advances.

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