Scientists discover the original home of the oldest Martian meteorite

The NWA 7034 meteorite, nicknamed Black Beauty, has fascinated geologists since its discovery in the Sahara Desert in 2011.

Scientists announced on Tuesday that they had found the crater from which the oldest known Martian meteorite was hurled towards Earth, a discovery that could provide clues to the formation of our own planet.

The NWA 7034 meteorite, nicknamed Black Beauty, has fascinated geologists since its discovery 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, which are nearly 4.5 billion years old.

“This makes it one of the oldest rocks studied in the history of geology,” Sylvain Bouley, a planetary scientist at Paris-Saclay University, told AFP.

Its journey dates back to the early days of the solar system, “about 80 million years after the planets began to form,” said Bouley, co-author of a new study on the meteorite.

The distribution of 90 million craters on the surface of Mars obtained from the crater detection algorithm. The colors indicate the size of the craters and their intensities are related to the density of the craters on the surface. Blue spots and radiating patterns are associated with the youngest and largest craters formed on the surface. The red circle identifies the Karratha crater that ejected the Black Beauty meteorite. Credit: Lagain et al, Curtin University

Tectonic plates had long covered the Earth’s ancient crust, meaning “we’ve lost that early history of our planet,” Bouley said.

But Black Beauty could offer “an open book on a 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 hitting the Red Planet that sent Black Beauty into space.

The impact “had enough force to eject the boulders at very high speeds – more than five kilometers (three miles) per second – to escape Martian gravity”, Anthony Lagain de Curtin, the study’s lead author in Nature Communicationtold AFP.

Such a crater should be massive – at least three kilometers in diameter.

The problem? The pockmarked surface of Mars has about 80,000 craters at least that big.

Follow the clues

But the researchers had a clue: By measuring Black Beauty’s exposure to cosmic rays, they knew she had been dislodged from her first home about five million years ago.

“So we were looking for a crater that was very young and big,” Lagain said.

Another clue was that its composition showed that it had suddenly warmed up around 1.5 million years ago, possibly from 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 had been unearthed from its first home by an asteroid that struck about 1.5 billion years ago, forming the 40 kilometer Khujirt crater.

Then a few million years ago, another asteroid struck not far away, creating the 10 kilometer Karratha crater and hurling the Black Beauty towards Earth.

The southern hemisphere region of Mars is rich in the elements potassium and thorium, as is Black Beauty.

Another factor was that Black Beauty is the only highly magnetized Martian meteorite.

“The region where Karratha was discovered is the most magnetized on Mars,” Lagain said.

Known as the province of Terra Cimmeria-Sirenum, it is “a relic of early crustal processes on Mars, and therefore a region of great interest for future missions”, according to the study.

Bouley pointed to a “bias” in currently planned missions to Mars in favor of searching for signs of water and life.

But understanding how planets first form would answer some fundamental questions, Lagain said, including “how Earth became such an exceptional planet in the Universe.”

Machine learning identifies the crater that ejected the famous Martian rock

More information:
Anthony Lagain, First crustal processes revealed by the ejection site of the oldest Martian meteorite, Nature Communication (2022). DOI: 10.1038/s41467-022-31444-8.

© 2022 AFP

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