A roughly two-pound rock picked up in the Sahara Desert in 2022 has been identified as a piece of the Martian crust at least 4.1 billion years old, according to WIRED. A set of studies published in the journals Science and Science Advances reports that the meteorite, named Teghaza 001, also carries chemical evidence of ancient water interacting with the planet's rock.
The fragment was most likely blasted off Mars by an impact and drifted through space before landing on Earth. WIRED reports that it is among the oldest known samples of our neighboring planet.
Why it matters
Most Martian meteorites found on Earth tell scientists about the composition and geological history of Mars, but they offer little about what conditions on the planet were actually like long ago. According to WIRED, Teghaza 001 is different: it has retained chemical signatures of the exchange between material in the Martian crust and the planet's ancient hydrosphere.
Yang Liu of NASA's Jet Propulsion Laboratory, quoted in a press release, said a reviewer of the research described the meteorite as a Rosetta Stone for Mars.
The find lands at a moment when a central question about Mars is whether its past water could have supported microscopic life, and what happened to turn a once hospitable planet into the cold, barren world it is today. Space missions have amassed evidence that Mars once had rivers, lakes and possibly larger bodies of water, but how the planet changed over billions of years remains unresolved. WIRED notes that answering that question is part of the rationale for sending probes and rovers there, and perhaps one day crews.
What the crystals preserved
Tiny crystals of a mineral called apatite inside the meteorite hold signatures of hydrogen from two distinct sources, according to WIRED: one from Mars' interior and one tied to its ancient hydrosphere. In other words, the rock contains material that was altered by a water-rich environment.
Because the sample dates to only about 500 million years after Mars and the rest of the solar system formed, the research indicates this mixing of deep magma and a watery surface happened very early in the planet's history.
Lee Saper, another NASA scientist involved in the work, said the meteorite is the first piece of Martian crust from a region of the planet that scientists have never had a sample of before. He added that it records water-rock interactions and possibly even an imprint of the Martian atmosphere as the planet was losing its water.
At the time the rock formed, Earth was a young and geologically restless planet, likely with oceans but without animals, plants or other complex life, WIRED reports.
A desert that keeps giving
The Sahara is a well-established source of such finds. WIRED notes that its sands have yielded 40-million-year-old fossils and other meteorites, including a 4.5-billion-year-old fragment recovered in 2019 that recent research suggests may have come from an ancient, now-vanished protoplanet possibly as large as the moon. Teghaza 001 could have ended up as one more entry in the catalog of Martian rocks collected on Earth; instead, the journal studies showed it stands apart.
WIRED's report originally appeared in WIRED en Español and was translated from Spanish.
The next step is for other researchers to build on the published analyses of Teghaza 001 and compare its chemistry with data from Mars orbiters and rovers, which could sharpen the picture of when and how the planet's water disappeared.
