A rare Martian meteorite could rewrite our theory of how planets form

It was 8 a.m. on October 3, 1815 when a space rock was seen mercilessly falling from the sky in Chasigny, northeastern France, accompanied by thunderous explosions that shook the earth. The meteorite, which originated on Mars, was called Chassigny, and it turned out to be not an ordinary rock.

A recent analysis of the meteorite led by Sandrine Péron, a postdoctoral researcher at ETH Zürich, Switzerland, revealed results that hint at how rocky planets like Earth and Mars obtained volatile elements (that make up life), including hydrogen, carbon, oxygen and nitrogen. and noble gases.

But these findings conflict with our basic understanding of how our planets were formed, according to a recent study published in the journal Sciences.

In other words, this could change much of what we know about planetary science.

It turns out that Mars formed faster than Earth

Mars is of particular interest to those who study early planetary formation. “Earth formation took approximately 50 to 100 million years,” said Professor Sujoi Mukhopadhyay of the Department of Earth and Planetary Sciences at the University of California, Davis. in another meaning in an interview. “Mars, on the other hand, formed much faster, within a few million years. So Mars could provide us with a window into the fluctuating delivery and buildup in the inner solar system during the early stages of planet formation.”

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“We can reconstruct the fluctuating delivery history in the first millions of years of the solar system,” Sandrine Peron, who works with Mukhopadhyay, said in a statement.

Older models and their observations of planet formation

According to current models, planets are born from the debris of a star. The collected dust contains carbon and iron, which are necessary for the formation of planetary systems. Around a new star, clumps of material collide and collapse onto each other in a swirling disk of gas and dust called the solar nebula.

Inside the disk, dust and gas huddle together in a process that evolves into a protoplanet. However, not all of these bodies turn out to be planets – some masses remain as small and inactive as asteroids and comets.

Models indicated that “as the planet grows and reaches the size of Mars, or somewhat larger, the growing planet can capture nebulous gases from the swirling gas cloud in which the planets grow and melt these gases into the magma ocean,” Mukhopadhyay said. .

Current hypotheses state that rocky planets contain elements with similar chemical properties in both the planet’s interior and atmosphere. Some volatile items later discharge Back to the atmosphere.

As the ocean of magma – which covers the planet – cools, the “nebula signature” is imprinted into the planet’s interior. Additional volatiles are also delivered to the atmosphere when meteorites collide with the young planet.

“After the nebula dissipates, cartilaginous volatiles (including water, carbon and nitrogen) are transported to the planets,” said Mukhopadhyay.

These volatiles are essential – on Earth, they helped develop and support life.

Among the planets, Jupiter and Saturn are believed to take the lead among their “peers”. They formed quickly – during the first few million years of the solar system’s existence.

After the gas giant planets formed, there wasn’t much gas left for planets like Mercury, Venus, Earth, and Mars. The formation of most of these took another tens of millions of years. but, Mars is of particular interest because it is believed to have froze about 4 million years after the birth of the solar system, roughly 50 to 100 million years before the Earth formed.

New study of an ancient space rock

For their study, Peron and Mokupadhyay compared two Martian sources of the noble gas krypton, the analogues of which contain information about the sources of volatiles.

One was from Chassigny, which originated in the interior of Mars. Other used isotopes of krypton have been sampled from the Martian atmosphere by NASA’s Curiosity Rover.

“This specific meteorite, Chassigny, is the only one from a noble gas point of view that can give access to the inner formation of Mars,” Perron said. vice. “All other Martian meteorites currently in the group are totally or severely influenced by the composition of the Martian atmosphere. If we want these pure interior components, it is the only meteorite we have so far.”

Now, because of the low abundance of krypton, it is difficult to measure and difficult to separate from argon and xenon. However, Péron and Mukhopadhyay used a new technology, which uses a cryogenic method to “cleanly” separate gas. “In addition, we used the latest generation mass spectrometer to accurately measure krypton isotopes,” Mukhopadhyay revealed.

To their surprise, the krypton signatures did not match.

Because krypton is like an atmosphere [that also found in] Sun, we certainly did not expect to find krypton from chondrite meteorites in the interior of Mars. “It seemed a bit retarded to us that there are meteorite gases in the interior and solar (nebulae) gases in the atmosphere,” Mukhopadhyay said.

(The chondrite meteorite was the one that was Formed when dust and small grains accumulated in the early Solar System and did not dissolve.)

Mukopadhyay said the team’s observations of the meteorite challenged the sequence of events for fluctuating delivery and accretion “by indicating that cartilaginous volatiles are not only added in the final stages of planet formation.”

Surprising details have been revealed in the heart of rocky planets

The results showed that the Martian atmosphere could not be formed solely by “releasing gases from the mantle, as that would give the atmosphere a cartilaginous formation,” Mukhopadhyay explained.

Researchers believe that the planet must have gained its early atmosphere from the solar nebula after the magma ocean had cooled and at least partially solidified.

“We suggested that the accumulation of solar gases from the nebula occurred after the solidification of the magmatic ocean, to prevent the significant mixing of the intrinsic and solar gases in the atmosphere, as the solidification of the magmatic ocean causes a large discharge of gases. If Mars had to capture nebulous gases from the early atmosphere after Partial solidification of the magma ocean, this indicates that the growth of Mars was completed before the nebula dissipated due to irradiation from an early active Sun,” explained Mukhopadhyay.

Accordingly, the order of events would be that Mars gained an atmosphere from the solar nebula after the global ocean of magma cooled. Else, the nebular and chondrite gases would be more mixed than the team discovered.

Then Mukhopadhyay added: “Our observations mean that meteorites were transporting volatile elements to Mars much earlier than previously thought and in the presence of the nebula. Our observations also indicate that Mars formation was completed before the nebula dissipated (the nebula dissipates due to radiation from the active Sun in the early time). “

But this raises another mystery.

Irradiation from the Sun was supposed to blow up the nebulous atmosphere on Mars, “requiring that the krypton present in the atmosphere be somehow preserved, possibly trapped underground or in polar ice caps. However, this would require that Mars be Too cold in the immediate aftermath. From her buildup.”

Breaking the theory about the formation of planets

The study confirms that there is a lot to learn about planet formation.

“Our study raises intriguing questions about how the early Martian atmosphere was formed, what was its composition, and whether surface environments on Mars might have been suitable for early habitability,” Mukhopadhyay said.

Knowing how the volatile elements are acquired and distributed is also essential to understanding the planet’s chemical makeup, said Chris Ballentine of the University of Oxford. new world. “The timing and source of volatiles control the state of oxidation, which in turn controls the structure and distribution of elements in the planet, which is what makes us live on it relative to our Earth.”

Scientists hope to make further observations of other Martian meteorites to get a detailed picture of their interior composition.