Rocks falling from Mars to Earth may change our understanding of planet formation

A small piece of rock that fell from Mars to Earth more than 200 years ago could contain information that could change everything known so far about our neighbor. Not only that: New analysis of the Chassigny meteorite shows that the way the planet acquires volatile organic compounds (VOCs), such as carbon, oxygen, hydrogen, nitrogen and noble gases, often contradicts our current models of planet formation.

Image: Valugi – Creative Commons

According to current models, planets are born from the remains of stars. Stars, in turn, form from nebulae, as the clouds of dust and gas created when dense clumps of matter collapse into the universe are well known.

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This material forms a disk that orbits the new star. Inside this disk, dust and gas begin to gather, forming a “baby planet.” Evidence in our solar system suggests that it formed the same way about 4.6 billion years ago.

However, how and when certain elements were incorporated into planets has been difficult to understand. According to current models, volatile gases are absorbed the moment the planet is born from the nebula, dragged from the early stages of the planetary body into the magma ocean, and then partially degassed into the atmosphere as the mantle cools.

Artist’s illustration of a planetary nebula. The interior of a planet must reflect the composition of the nebula that produced it. Image: Claudio Caridi – Shutterstock

Later, more gas was released by meteorite bombardment—volatiles bound to carbonaceous meteorites (called chondrites) were released as these rocks broke down on the developing planet.​​​

Thus, a planet’s interior must reflect the composition of the nebula that produced it, while its atmosphere must primarily reflect the meteorite’s volatile contribution. Differences between these two sources can be determined by examining the isotopic ratios of noble gases, especially krypton.

Meteorites break away from mantle, representing the interior of Mars

Because Mars formed and solidified in about 4 million years — a relatively quick process compared to the 100 million years it took Earth to form — it’s a good benchmark for analyzing these early stages of planet formation.

“We can reconstruct the wave transfer history of the first few million years of the solar system,” says geochemist Sandrine Péron of ETH Zurich (ETH Zurich). That is, of course, only if we have access to the information we need. – This is where the Chassigny meteorite achieved true “gift from space” status.

Its gas composition differs from that of the Martian atmosphere, suggesting that the rock is detached from the mantle and represents the planet’s interior, hence the solar nebula.

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According to the website Science Alert, The measurement of krypton is rather complicated, so the isotope ratio confounds the analysis. However, a team led by Péron and UC Davis geochemist Sujoy Mukhopadhyay used an innovative technique that noble gas laboratory New, accurate measurements of krypton on the Chassigny meteorite from UC Davis.

The ratios of krypton isotopes in meteorites are closer to those associated with chondrites, according to the new analysis. “The Martian interior of Krypton is almost purely spherulite, but the atmosphere is solar,” Perron said. “It’s very different.”

This suggests that meteorites delivered volatiles to Mars much earlier than scientists previously thought, that is, before solar radiation dissipated the nebula.

Thus, the sequence of events would be that Mars inherits its atmosphere from the solar nebula after its global ocean of magma cools. Otherwise, the spherulite gas and nebular gas would be more uniform than what the team observed.

However, this brings more mystery to the story. When solar radiation finally burned the remnants of the nebula, it must have also burned the atmosphere of Mars. That means the atmospheric krypton that came later must be preserved somewhere: perhaps in polar ice caps, the team suggests.

“However, this would require Mars to cool immediately after its accretion,” Mukhopadhyay said. “While our study clearly points to spherulite gas in the interior of Mars, it also raises some interesting questions about the origin and composition of Mars’ early atmosphere.”

More research should be done to complement the findings of this recent study published in the journal science.

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