PARIS | Scientists have identified the region of origin of a Martian meteorite, a veritable “open book” on the first moments of planet Mars that may be rich in lessons about Earth’s formation.

• Also read: NASA unveils all first images from the world’s most powerful space telescope, the James Webb

• Also read: The first image from the James Webb telescope shows the very young Universe

“Black Beauty,” NWA 7034 from its nickname, has fascinated geologists since its discovery in the Sahara Desert in 2011. This block, easy to hold and weighing just over 300 grams before cutting, is “the oldest rock known we have, whether on Mars, but also almost on Earth,” planetologist Sylvain Bouley, who co-authored the study published in Nature Communications, told AFP.

It contains zircons, a type of mineral that is 4.48 billion years old. Or “roughly 80 million years after planet formation began” in the solar system, says Mr. Bouley, a professor in the Earth Sciences Laboratory at Paris-Saclay University.

NWA 7034 is thus an “open book on the first moments of Mars” when its magma surface began to solidify. While we’ve “lost this primitive history of our Earth,” where most of the original lands have disappeared, in the great revision of plate tectonics — a phenomenon that has largely spared Mars.

The research team, led by planetary scientists from Australia’s Curtin University in Perth and with a strong contribution from French institutions, managed to pinpoint the exact origin of the meteorite in a region that hosts a very primitive crust of the red planet.

He had to identify a crater formed by the impact of a fireball from space with “sufficient force to eject the rocks at very high speeds, more than 5 km/s, to escape Martian gravity,” explains Anthony Lagain , Planetary AFP scientist at Curtin University and first author of the study.

Such craters must have a diameter of at least 3 km. Problem, Mars has about 80,000 of at least that size.

Second, the researchers knew that NWA 7034 had been ejected into space about five million years ago, thanks to measuring its exposure to cosmic rays.

90 million photos of craters

“We were therefore looking for a very young and large crater,” says AFP Anthony Lagain, whose doctoral thesis dealt in particular with the dating of Martian craters.

Another clue, analysis of Black Beauty’s composition, revealed that it had been brutally heated 1.5 billion years ago, likely by an asteroid impact. In other words, the rock was first removed from the surface before falling further, where this time another impact into space propelled it all the way to Earth.

Armed with this information, Anthony Lagain improved a crater detection algorithm developed at Curtin. Before using a supercomputer to grind up the mosaic of 90 million photos of Martian craters collected thanks to a NASA satellite camera.

The result narrowed the selection down to 19 pits and then just one, Karratha. This 10 km diameter crater is located in “a very ancient region of the Southern Hemisphere rich in potassium and thorium, like Black Beauty,” says Mr. Lagain. Final argument, the meteorite is the only one of the Martians that is highly magnetized, but “the region where Karratha is located is the most magnetized on Mars.”

This area, spanning the Terra Cimmeria and Sirenum regions, is “probably a relic of the oldest crust on Mars,” according to the study. Who advocates sending a mission dedicated to the study of its geology.

Prof. Bouley points to a kind of “bias” that has focused the Mars missions on searching for traces of water and life, at the expense of earlier times that may have allowed their appearance. In addition, NWA 7034 made the front page after its discovery because of the water it contained.

However, to understand the formation of the first planetary crusts, one must understand what happened in the very beginning, Mr. Lagain recalls, and “how to arrive at a planet as extraordinary as Earth in the universe.”

Leave a Reply

Your email address will not be published.