Scientists find original home of oldest Martian meteorite

Meteorite NWA 7034, nicknamed Black Beauty, has fascinated geologists since it was discovered in the Sahara Desert in 2011.

Scientists announced Tuesday that they have discovered the crater where the oldest known Martian meteorite was originally blasted toward Earth, a discovery that could provide clues as to how our own planet formed.

Meteorite NWA 7034, nicknamed Black Beauty, has fascinated geologists since it was discovered in the Sahara Desert in 2011.

It fits in the hand, weighs over 300 grams (10.6 ounces), and contains a mix of materials including zircon, which is nearly 4.5 billion years old.

“That makes it one of the oldest rocks studied in geological history,” Sylvain Bouley, a planetary scientist at France’s University of Paris-Saclay, 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, who co-authored the new study on the meteorite.

The distribution of 90 million craters on the Martian surface is obtained from the Crater Detection Algorithm. The color indicates the size of the crater and its intensity is related to the density of the crater on the surface. The blue spots and light patterns are associated with the youngest and largest craters to form on the surface. The red circle shows the Karratha crater that ejected the Black Beauty meteorite. Credit: Lagain et al, Curtin University

Plate tectonics have long covered the ancient Earth’s crust, meaning that “we have lost the primitive history of our planet”, Bouley said.

But Black Beauty could offer “an open book about a planet’s first moments”, he added.

To open the book, a team of researchers at Australia’s Curtin University set out to find the meteorite’s original home on Mars.

They knew that it was highly likely that the asteroid hit the red planet sending Black Beauty shooting into space.

The collision “had sufficient force to eject rock at breakneck speed—more than five kilometers (three miles) per second—to escape Mars’ gravity”, Curtin’s Anthony Lagain, lead author of the study on Nature Communicationto AFP.

Such a crater must be very large—at least three kilometers in diameter.

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

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But the researchers have a clue: by measuring Black Beauty’s exposure to cosmic rays, they know it dislodged from its first home about five million years ago.

“So we’re looking for a very young and large crater,” said Lagain.

Another clue is that its composition suggests that it suddenly heated up about 1.5 million years ago—possibly by a second asteroid impact.

The team then built an algorithm and used a supercomputer to trace images of the 90 million craters taken by NASA satellites.

That narrowed it down to 19 craters, allowing the researchers to rule out any remaining suspects.

They found that Black Beauty was excavated from its first home by an asteroid that struck about 1.5 billion years ago, forming the 40-kilometer-long Khujirt crater.

Then a few million years ago, another asteroid hit not far away, creating a 10-kilometer-long Karratha crater and shooting Black Beauty toward Earth.

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

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

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

Known as Terra Cimmeria—Sirenum province, it is “a relic of early crustal processes on Mars, and as such, a very attractive region for future missions,” the study said.

Bouley points to a “bias” in the currently planned mission to Mars to look for signs of water and life.

But understanding how the first planets formed will answer some fundamental questions, Lagain said, including “how did Earth become the most extraordinary planet in the Universe”.

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Machine learning identifies crater that ejects famous Martian rock

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Further information:
Anthony Lagain, Early crustal processes revealed by oldest Martian meteorite ejection site, Nature Communication (2022). DOI: 10.1038/s41467-022-31444-8. www.nature.com/articles/s41467-022-31444-8

© 2022 AFP

Quote: Scientists find original home of oldest Martian meteorite (2022, 16 July) retrieved 16 July 2022 from https://phys.org/news/2022-07-scientists-oldest-martian-meteorite-home.html

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