Scientists find oldest Martian meteorite’s original home

PARIS

Scientists announced on July 12 they had found the crater from which the oldest known Martian meteorite was originally blasted towards Earth, a discovery that could provide clues into how our own planet was formed.

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

It fits easily in the hand, weighing just over 300 grams, and contains a mix of materials including zircons, which date back nearly 4.5 billion years.

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

Its journey dates back to the solar system’s infancy, “about 80 million years after the planets began forming,” said Bouley, who co-authored a new study on the meteorite.

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 likely an asteroid hitting the red planet that sent Black Beauty shooting up into space.

The impact “had enough force to eject the rocks at very high speed - more than five kilometers a second - to escape the Martian gravity,” Curtin’s Anthony Lagain, the lead author of the study in Nature Communications, told AFP.

Such a crater would have to be massive at least three kilometers in diameter. The problem? The pockmarked surface of Mars has around 80,000 craters at least that big.

But the researchers had a clue: By measuring Black Beauty’s exposure to cosmic rays, they knew it was dislodged from its first home around 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 it had suddenly heated up around 1.5 million years ago, likely by the impact of a second asteroid.

The team then created an algorithm and used a supercomputer to trawl through images of 90 million craters taken by a NASA satellite.

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

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

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