A 4.4-billion-year-old meteorite may be the first-known example of ancient Martian crust, and it could hold key plot points in the planet's storied history.
Bedouin tribesmen found the rock, nicknamed "Black Beauty," in the Sahara Desert. Scientists first studied the rock in February and initially estimated that it was about 2 billion years old. However, Florida State University Professor Munir Humayun and his team performed more complex experiments on a 3-pound sample and found it was much older.
"This date is about 100 million years after the first dust condensed in the solar system," Humayun said. "We now know that Mars had a crust within the first 100 million years of the start of planet building, and that Mars' crust formed concurrently with the oldest crusts on Earth and the Moon."
While meteorites from Mars are rare, Black Beauty is especially significant because it's relatively rich in water — about 6,000 parts per million, compared to 200 to 300 parts per million from other meteorites. Simply put, Black Beauty is tangible evidence that the Red Planet was once a wet, lush environment similar to Earth.
In his report published in the journal Nature, Humayun also noted that the rock contains high levels of trace metals like iridium, indicating it came from the Gusev crater area in Mars' southern highlands. Humayan said the rock is the result of a large meteorite that crashed into Mars billions of years ago, breaking up and ejecting pieces into space.
Full-size version of "Black Beauty" meteorite (R) and the Gusev crater on Mars, taken by NASA's Spirit rover (L). Images: NASA
Although argon exists throughout our solar system, Mars has a special ratio of light to heavy argon that proves the planet was once covered in water. However, the sun scraped away its thick atmosphere, turning it into the cold, dry, desolate planet we see today.
Humayun said similar experiments were conducted on Black Beauty to confirm its origin, but its composition is a rarity that will lead to more discoveries.
"This match cannot be made with other meteorite types," he said. "Even the ancient age of the zircons is younger than that measured in asteroidal basalts. There are even soil clots inside the meteorite that match the composition of Martian soil, a very unique composition."
The discovery is just one more piece to the puzzle of Mars' mysterious history.
Image: Luc Labenne