Martian meteorite found in Mali dates back 4.1 billion years: Study

Discovery in the desert

NASA-funded researchers have determined that a meteorite discovered in Mali's Sahara Desert in 2022 represents one of the oldest Martian rocks ever found on Earth, according to a study published Thursday in the journal Science. The roughly 800-gram specimen dates back more than 4.1 billion years.

Named Teghaza 001 after the salt plain where it was found, the rock initially appeared to belong to the common shergottite class of Martian meteorites. "It was only after we started looking closely that we realized this meteorite is really unique," said Yang Liu, the study's lead author and a researcher at NASA's Jet Propulsion Laboratory (JPL) in Southern California. "One of the paper's reviewers called it a Rosetta Stone for Mars."

Crust formation clues

Teghaza 001 stands among only three ancient Martian meteorites identified on Earth, alongside ALH84001 — which consists almost entirely of one mineral — and the 2.1-billion-year-old "Black Beauty." The meteorite contains a distinctive combination of igneous minerals that offer clues about how Mars' crust formed as magma cooled and was later altered by subsurface water, researchers noted.

"This is really our first piece of Martian crust from a part of Mars we've never had a sample of before," said Lee Saper, the study's second author and a scientist at NASA's Ames Research Center. He stated that the specimen "records interactions of water and rock and maybe even an imprint of the Martian atmosphere as it was losing water."

Ancient water cycle

Researchers at the University of New Mexico initially identified the meteorite as Martian by analyzing its oxygen isotopes, but further investigation revealed zircon crystals that preserve information about the rock's formation. Francois Tissot, a co-author from the California Institute of Technology, applied an in-situ rubidium-strontium dating technique to individual mineral grains using a fragment smaller than a fingernail, which showed water altered the rock around 4.1 billion years ago.

"Right now, we are one of very few labs in the world able to perform this kind of age-dating, and the first to date such an ancient Martian meteorite," Tissot said. "We've only scratched the surface," Liu added, noting that further studies could clarify how water shaped the planet's early geological history.