A roughly two-pound rock picked up in the Sahara Desert in 2022 has been identified as one of the oldest known pieces of Mars, and new research says it carries chemical evidence of the planet's ancient water. The meteorite, named Teghaza 001, is at least 4.1 billion years old and came from the Martian crust, according to WIRED. Findings from a set of studies appeared in the journals Science and Science Advances.
The rock was most likely blasted off Mars by an impact and traveled through space before landing on Earth. When it formed, Earth was still a young planet with heavy geological activity, oceans, and no complex life.
Why it matters
Martian meteorites already on Earth are valuable for studying what Mars is made of and how its geology developed, but they usually say little about what conditions were like on the planet long ago. WIRED reports that Teghaza 001 is different: it has kept chemical traces of material from the Martian crust interacting with the planet's ancient hydrosphere.
Yang Liu of NASA's Jet Propulsion Laboratory, in a press release, said one of the paper's reviewers described the meteorite as a Rosetta Stone for Mars.
The sample dates to about 500 million years after Mars and the rest of the solar system formed, which means the water-rock exchange it records happened very early in the planet's history. Scientists have long known that Mars once had liquid water on its surface. Two of the major open questions are whether that water ever supported microscopic life and what turned the planet into the cold, dry world it is today.
What the crystals preserve
According to WIRED, tiny crystals of a mineral called apatite inside the meteorite hold signatures of two different sources of hydrogen. One came from Mars' interior; the other is tied to the planet's ancient hydrosphere. In effect, the rock contains material that was changed by an environment rich in water.
Lee Saper, another NASA scientist involved in the work, said the sample is the first piece of Martian crust from a region of the planet that researchers have never had a sample from before. He said it records rock interacting with water and possibly even a trace of the Martian atmosphere as the planet was losing its water.
The Sahara has a long record of yielding significant finds. Its sands have produced fossils around 40 million years old as well as other meteorites. In 2019, a fragment 4.5 billion years old was recovered that, per recent research, may have come from an ancient protoplanet that no longer exists and may have been as large as the Moon.
Space missions have gathered evidence of rivers, lakes, and possibly larger bodies of water on early Mars. How the planet changed over billions of years is still unexplained, and that question is part of the reason agencies send orbiters and rovers there and hope eventually to send crews. WIRED notes that sometimes the answers arrive through improbable meteorites instead.
The studies were published in Science and Science Advances. WIRED's report originally appeared in WIRED en Español and was translated from Spanish.
Watch for follow-up work on Teghaza 001's chemistry and for other samples from the same region of Mars, which could sharpen the picture of when and how the planet's water disappeared.
