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The crust that surrounds the rocky planets and makes possible the emergence of life took shape on Mars earlier than expected, and at least 100 million years earlier than Earth, researchers said Wednesday.
By badyzing the coarse extrados zircon of a Martian meteorite known as Black Beauty, the researchers determined that the outer layer of the red planet hardened 4.547 billion years ago, only 20 million years after the birth of the Sun.
"The initial formation of the Martian crust – which is the final product of the global formation – has occurred much more quickly than previously thought," said Martin Bizzarro, researcher at the Star Training Center. and planets in Denmark. in the scientific journal Nature.
"Our results indicate that Mars may have had an environment with the oceans, and potentially life, well before Earth," AFP said.
Water is considered an essential precursor of life as we know it.
Mars has already been much more similar to the Earth, with a thick atmosphere, abundant water and oceans.
Until now, mathematical models have suggested that the solidification of the red planet has taken up to 100 million years.
The new study addresses the issue by examining a piece of Mars that has entered the Sahara Desert and was discovered in 2011.
The Black Beauty meteorite weighed 320 grams when it was found. The researchers protected 44 grams of rock from the precious space and crushed five – enough to extract seven pieces of zircon that could be used in experiments.
– "Time Capsule" –
By measuring the decay of lead from uranium that was trapped in zircon when the molten magma of young Mars was hardened, scientists were able to accurately determine the crust from which zircon was found. 39 is formed.
"I'm glad we chose this strategy," Bizzarro said. "Zircon as a time capsule".
There are two main models for the formation of the planet.
In one, it occurs in stages, with small particles of dust agglutinating into "planetesimals" – rock fragments 10 to 100 kilometers in diameter – colliding to form planetary embryos, then planets, on a scale of 50 to 100 million years.
According to a more recent model, global growth is growing faster and is fueled by the so-called "acreo de peixos", the accumulation in particle layers measured in centimeters and meters that are weakly related to gases.
"Our data supports more recent models that indicate the very fast formation of terrestrial planets," said the authors.
The new timeline suggests that something similar may have happened on our planet, but only after the Earth was "redefined" by the giant impact that formed the moon about 4.4 billion years ago. 39 years, said Bizzarro.
It is thought that Mars has a dense metal core with a radius of about 1800 kilometers, composed mainly of iron, nickel and sulfur.
The core is surrounded by a largely dormant mantle – about 1500 km thick – composed mainly of silicon, oxygen, iron and magnesium.
Finally, the crust measures on average 50 km deep, with a maximum of about 125 km. The earth's crust has an average of 40 km, but accounts for one third of the thickness of the Martian crust when the size of the planet is taken into account.
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