Ancient Martian meteorite discovered in Mali formed over 4.1 billion years ago: Study

A meteorite discovered in Mali in 2022 dates back more than 4.1 billion years, offering scientists rare insights into Mars' ancient crust and water history, according to a recent study.

NASA-funded researchers have determined that Teghaza 001, an approximately 800-gram (1.8-pound) meteorite found in the Sahara Desert, originated on Mars and is among the oldest Martian meteorites ever discovered on Earth.

Named after the salt plain in Mali where it was discovered, it is one of roughly 435 known Martian meteorites. The findings were published Thursday in the journal Science, according to NASA's Jet Propulsion Laboratory (JPL).

The study provides an initial characterization of the meteorite, which contains a distinctive combination of igneous, or volcanic, minerals. These minerals offer clues about how Mars' crust formed as magma cooled and was later altered by subsurface water. A separate study published in Science Advances in June examined the meteorite's water content and its implications for the planet's early surface.

"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 JPL in Southern California. "One of the paper's reviewers called it a Rosetta Stone for Mars."

Teghaza 001 is among the three most ancient Martian meteorites found on Earth. The others include ALH84001, which is composed almost entirely of one mineral and is of a similar age, and "Black Beauty," which formed about 2.1 billion years ago.

The meteorite's mineral composition resembles material observed by NASA's Mars Reconnaissance Orbiter in the planet's cratered southern highlands. Although its exact origin remains unknown, researchers identified several potential locations consistent with its mineralogy and chemistry.

"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, who conducted the research as a postdoctoral scholar at JPL and is now a scientist at NASA's Ames Research Center in Silicon Valley.

"It records interactions of water and rock and maybe even an imprint of the Martian atmosphere as it was losing water," Saper said.

Evidence of ancient water

Researchers at the University of New Mexico initially identified Teghaza 001 as Martian by analyzing its oxygen isotopes, which act as geochemical fingerprints. It appeared to belong to the shergottite class, the most common type of Martian meteorite.

However, Liu noticed unusual textures and minerals that warranted further investigation. Her team discovered zircon crystals, which preserve information about a rock's formation and help scientists determine its age.

Francois Tissot, a co-author from the California Institute of Technology, helped apply an in-situ rubidium-strontium dating technique developed by his team. The method analyzes individual mineral grains using a fragment smaller than a fingernail, preserving most of the rare meteorite for future research.

"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. "Our hope is to pave the way for dating even more Martian meteorites, or samples returned from other planets, their moons and asteroids."

The results showed that water altered the rock around 4.1 billion years ago, suggesting it originally formed even earlier. Evidence from its oxygen isotopes, texture and chemistry points to a dynamic water cycle on early Mars.

Researchers say further studies of Teghaza 001 could help clarify how water interacted with rocks and shaped the planet's early geological history.

"We've only scratched the surface," Liu said.