What secrets does he keep? Scientists have recently identified the source of a Martian meteorite, which they believe is an “open book” to Mars’ early days. Red Planet material is potentially rich in lessons about Earth’s formation.
“Black Beauty,” as NWA 7034 is nicknamed, has fascinated geologists since its discovery in the Sahara in 2011.
“Oldest” Martian rocks
The block, weighing just over 300 grams before being easily picked up and cut, is “our oldest rock, not only on Mars but also almost on Earth”, explained paleontologist Sylvain Bolly, who co-authored the published study, to AFP. Tuesday in Nature communication On this topic.
It contains zircon, a mineral that is 4.48 billion years old. Or “about 80 million years after the start of the formation of planets” in the solar system, said Sylvain Bolly, a professor at the Geosciences Laboratory at the University of Paris-Saclay.
NWA 7034 is thus an “open book of Mars’ first moments,” when its magma surface began to solidify. Although we have “lost this primitive history of our Earth”, where most of the original landmasses have disappeared, in the great reshaping of plate tectonics – an event that has largely preserved Mars.
A crater located in the southern hemisphere of Mars
The team of researchers, led by planetary scientists from Curtin University in Perth, Australia, with a strong contribution from French institutions, succeeded in pinpointing the origin of the meteorite in a region hosting a very primitive crust from the Red Planet.
He was to identify a crater, formed by the impact of a meteor from space “enough to escape the gravity of Mars, ejecting rock at very high speeds, more than 5 km/s”. Curtin University scientist and first author of the study. The diameter of such crater should be at least 3 km. Problem is, Mars has at least 80,000 of this size.
As a second clue, researchers knew that NWA 7034 was ejected into space about five million years ago, thanks to measurements of cosmic ray exposure. “So we were looking for a very young and large crater,” said AFP’s Anthony Lagain, whose doctoral thesis focused specifically on the dating of craters on Mars.
Another source, analysis of the composition of “Black Beauty”, suggests that it was violently heated 1.5 billion years ago, possibly by an asteroid impact. In other words, the rock was first lifted off the surface before it fell further, where another impact this time threw it into space, all the way to Earth.
Armed with this information, Anthony Lagain developed a crater detection algorithm developed in Curtin. He created a mosaic of 90 million photos of craters on Mars, thanks to a NASA satellite camera, before being crunched by a supercomputer.
The result narrowed the choice down to 19 pits and then just one, Karratha. The 10-kilometer-diameter crater “is located in a very old region of the Southern Hemisphere, as rich in potassium and thorium as Black Beauty,” says Anthony Lagain. The final argument is that only Martian meteorites are highly magnetized, but “the region where Karratha is located is the most magnetized on Mars”.
“Understanding What Happened in the Beginning”
The region, spanning the Terra Cimmeria and Sirenum regions, is “probably a remnant of the oldest crust on Mars”, according to the study. who petitioned to send a mission devoted to studying its geology.
Professor Boley pointed to a kind of “bias” that made Mars missions focus on searching for signs of water and life, at the expense of earlier times, which would have allowed their appearance. Moreover, after its discovery, NWA 7034 made headlines due to the presence of water in it.
However, understanding the formation of the crust of the first planets requires understanding what happened at the very beginning, recalls Anthony Lagain, and “how we arrived at exceptional planets like Earth in the universe”.