Scientists announced Tuesday that they have found the crater from which the oldest known Martian meteorite was originally ejected toward Earth, a discovery that could provide clues to how our own planet formed. Nicknamed the Black Beauty, meteorite NWA 7034 has fascinated geologists since it was discovered in the Sahara desert in 2011. It fits easily in the hand, weighs just over 300 grams (10.6 ounces) and contains a mixture of materials including zircons that are nearly 4.5 billion years old.”This makes it one of the oldest studied rocks in the history of geology,” Sylvain Bouley, a planetary scientist at France’s Paris-Saclay University, told .
Its path goes back to the early days of the solar system, “about 80 million years after the planets began to form,” said Bouley, who co-authored the new study on the meteorite. Plate tectonics have long since covered the ancient Earth’s crust, meaning “we’ve lost this primitive history of our planet,” Bouley said. But Black Beauty could offer “an open book on the planet’s first moments,” he added.To open this book, a team of researchers from Australia’s Curtin University set out to find the meteorite’s original home on Mars.
They knew it was probably an asteroid that hit the red planet and shot Black Beauty into space. The impact “had enough force to hurl the rocks at very high speeds – more than five kilometers (three miles) per second – to escape Martian gravity,” Curtin’s Anthony Lagain, lead author of the study in Nature Communications, told AFP. Such a crater would have to be massive – at least three kilometers in diameter.Problem? The cracked surface of Mars has about 80,000 craters, at least this large. But scientists had a clue: by measuring Black Beauty’s exposure to cosmic rays, they knew it had been pushed out of its first home about five million years ago.”So we were looking for a crater that was very young and large,” Lagain said. Another clue was that its composition showed that it had suddenly warmed up about 1.5 million years ago – probably by the impact of a second asteroid.
The team then created an algorithm and used a supercomputer to sift through images of 90 million craters taken by a NASA satellite. This narrowed it down to 19 craters, allowing researchers to rule out the remaining suspects.They discovered that Black Beauty was dug out of its first home by an asteroid that struck about 1.5 billion years ago, creating the 40-kilometer-long crater Khujirt. A few million years ago, another asteroid struck not far away, creating the 10-kilometer crater Karratha and shooting Black Beauty toward Earth.
The area in the southern hemisphere of Mars, like Black Beauty, is rich in the elements potassium and thorium. Another factor was that Black Beauty is the only Martian meteorite that is highly magnetized.”The area where Karratha was found is the most magnetized on Mars,” Lagain said. Known as the Terra Cimmeria-Sirenum province, it is “a relict of early crustal processes on Mars and thus an area of ​​great interest for future missions,” the study said. Bouley pointed to a “bias” in currently planned missions to Mars in favor of searching for signs of water and life.But understanding how the first planets formed would answer some fundamental questions, Lagain said, including “how Earth became such an exceptional planet in the universe.”
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