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A meteorite that landed on Earth 200 years ago upends previous theories about the formation of Mars

A meteorite that hit Earth more than 200 years ago could fundamentally change our understanding of how Mars formed.

Most of what we know about the Red Planet’s interior comes from three space rocks that landed on our planet after being thrown from Mars by impacts.

These include the Chassingy meteorite, which fell in northeastern France in 1815, and two others known as Shergotty and Nakhla.

A new analysis from Chassingy suggests that Mars’ interior chemical makeup largely comes from meteor collisions, rather than a giant cloud of gas called the Solar Nebula as previously thought.

This contradicts current thinking about how rocky planets like Earth and Mars acquire volatile elements such as hydrogen, carbon, oxygen, nitrogen, and noble gases as they form.

Mars is of particular interest because it formed relatively quickly – solidifying about 4 million years after the birth of the solar system, while Earth took 50 to 100 million years to form.

Discovery: A new analysis of the Chassingy meteorite (pictured) suggests that Mars' interior chemical composition largely comes from meteorite collisions, rather than a giant cloud of gas called the Solar Nebula as previously thought

Discovery: A new analysis of the Chassingy meteorite (pictured) suggests that Mars’ interior chemical composition largely comes from meteorite collisions, rather than a giant cloud of gas called the Solar Nebula as previously thought

MARCH: THE BASICS

Mars is the fourth planet from the sun, with a dusty, cold and “nearly dead” desert world with a very thin atmosphere.

Mars is also a dynamic planet with seasons, polar caps, canyons, extinct volcanoes, and evidence that it was even more active in the past.

It is one of the most explored planets in the solar system and the only planet that humans have sent rovers to explore.

A day on Mars lasts just over 24 hours and a year has 687 Earth days.

Facts and figures

Orbital period: 687 days

Area: 144.8 million km²

distance from the sun: 227.9 million km

Gravity: 3.721 m/s²

Ray: 3,389.5 km

Moons: Phobos, Deimos

Scientists had thought that the newly formed worlds first collected these volatiles in the nebula around a young star, before the elements initially dissolved into an ocean of magma, then outgassed into the atmosphere as that the planet is still a ball of molten rock.

The theory assumes that later chondritic meteorites crashing into the young planet deliver more volatile material.

It was believed that the volatiles inside the planet must reflect the composition of the solar nebula, or a mixture of solar and meteoritic volatiles, while the volatiles in the atmosphere would come mainly from the meteorites.

This was supported by previous Chassingy research that looked at isotopes of xenon, a chemically inert gas that can survive unchanged for millions of years.

The isotopic ratios of the meteorite appeared to match those of the atmosphere of Mars and the solar nebula, leading to the hypothesis that its volatile elements, such as hydrogen, carbon and oxygen, came from the solar nebula and that additional elements came later from meteorites.

However, the new study by researchers at the University of California, Davis disputes this.

They analyzed a sample from Chassigny, but this time looked at isotopes of krypton – a different inert gas that allows more precise measurements.

“With xenon isotopes, it is difficult to distinguish the precise source of the volatiles, but this is not the case with krypton,” one of the study’s authors, Sandrine Péron, told New Scientist.

“With krypton you can better see the difference between potential sources like the sun or meteorites…but krypton isotopes are harder to measure than xenon isotopes, so that’s why it hadn’t been done before. .”

The researchers found that the isotopes came from meteorites rather than the solar nebula.

This means that the meteorites delivered volatile elements to the forming planet much earlier than previously thought, and in the presence of the nebula, reversing conventional thinking.

Mars is of particular interest because it formed relatively quickly - solidifying about 4 million years after the birth of the solar system, while Earth took 50 to 100 million years to form.

Mars is of particular interest because it formed relatively quickly – solidifying about 4 million years after the birth of the solar system, while Earth took 50 to 100 million years to form.

“The Martian interior composition of krypton is almost purely chondritic, but the atmosphere is solar,” Péron said. “It’s very distinct.”

The results show that Mars’ atmosphere cannot have formed solely by outgassing from the mantle, as that would have given it a chondritic composition.

The planet must have acquired the atmosphere of the solar nebula, after the magmatic ocean had cooled, to prevent substantial mixing between interior chondrite gases and atmospheric solar gases.

The new results suggest that Mars’ growth was completed before the solar nebula was dissipated by solar radiation.

But the irradiation should also have been blowing through Mars’ nebular atmosphere, suggesting that atmospheric krypton must have been preserved somehow, possibly trapped underground or in polar ice caps.

“However, this would require Mars to have been cold immediately after accretion,” Mukhopadhyay said.

“While our study clearly points to chondritic gases inside Mars, it also raises interesting questions about the origin and composition of Mars’ early atmosphere.”

The study was published in the journal Science.

Explained: the difference between an asteroid, a meteorite and other space rocks

A asteroid is a large piece of rock left over from collisions or the early solar system. Most are located between Mars and Jupiter in the main belt.

A comet is a rock covered with ice, methane and other compounds. Their orbits take them much farther from the solar system.

A meteor is what astronomers call a flash of light in the atmosphere when debris burns.

These debris themselves are known as meteoroid. Most are so small that they vaporize into the atmosphere.

If one of these meteoroids arrives on Earth, it is called a meteorite.

Meteors, meteoroids and meteorites normally come from asteroids and comets.

For example, if the Earth passes through the tail of a comet, much of the debris burns up in the atmosphere, forming a meteor shower.

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