Paris | A veritable “open book” on Mars’ first moments, scientists have identified the site of a Martian meteorite full of lessons about Earth’s formation.
The “Black Beauty”, nicknamed NWA 7034, has fascinated geologists since its discovery in the Sahara in 2011. The block, which weighed more than 300 grams before it was cut, “is the oldest rock we have. On Mars but also almost on Earth,” astronomer Sylvain Bouley, who co-signed the study published in Nature Communications, told AFP.
It contains zircons, a type of mineral that is 4.48 billion years old. Or about 80 million years after the solar system’s “planets began to form,” says Mr. Paulie.
NWA 7034 is an “open book on Mars’ first moments,” when its magma surface began to solidify. We’ve “lost this ancient history of our Earth,” where most of the original landmasses have disappeared, in a major reworking of plate tectonics—which largely spared Mars.
A team of researchers led by planetary scientists from Curtin University in Perth, Australia, with strong contributions from French institutions, has succeeded in determining the precise origin of a meteorite in a region that provides the oldest crust from the Red Planet.
He had to identify a crater created by the impact of a fireball from space “with enough force to eject rocks at speeds exceeding 5 km/s to escape the gravity of Mars.” , AFP Anthony Lagain, Curtin University scientist and first author of the study explains to Planet.
Such ditches should be at least 3 km in diameter. The problem is, Mars has at least 80,000 of this size.
A second clue is that researchers knew NWA 7034 was ejected into space five million years ago, thanks to measurements of exposure to cosmic rays.
Photographs of 90 million craters
“So we’re looking for a very young and large crater,” says AFP’s Anthony LaCain, whose doctoral research focused on the dating of Martian craters.
Another clue, analysis of the “Black Beauty” composition, revealed that it was brutally heated 1.5 billion years ago, possibly by an asteroid impact. In other words, the rock was extracted from the surface before falling further, this time by another impact that threw it into space, all the way to Earth.
Armed with this information, Anthony Lagain improved the crater detection algorithm developed at Curtin. A mosaic of 90 million Martian crater photos were collected by a NASA satellite’s camera before being processed on a supercomputer.
This reduced the selection to 19 holes and then just one karrada. The 10km-diameter crater is “a black beauty rich in potassium and thorium, one of the oldest in the southern hemisphere,” says Mr Lagain. The final argument is that only the Martian meteorite is the most magnetic, but “the area where Karratha is located is the most magnetic on Mars”.
The region, which spans Terra Cimmeria and Sirenum, “may be a relic of the oldest crust on Mars,” according to the study. who begs to send a mission devoted to its geological study.
Prof. Bouley points to a kind of “bias” that has focused Mars missions on looking for water and traces of life, at the expense of earlier times, which may have allowed their appearance. Also, after its discovery, NWA 7034 made the front page because it contains water.
However, understanding the formation of the first planetary crusts and what happened in the beginning, Mr. Lagain recalls, and “how does one come to a planet like Earth in the universe”.