Rare meteorites improve the theory of the formation of Mars

A single meteorite on Mars contains unexpected chemistry that could improve scientists’ models of how Earth’s planets formed, according to a new study of an old space rock.

The chemical traces in this remote sample suggest that Mars and Earth – often seen as twins because they are rocky worlds and solar systems – were born in very different ways: the Earth formed slowly, and Mars much faster.

Current hypotheses about the formation of a rocky planet, such as Mars or Earth, suggest that some elements inside the planet must have the same chemical properties as the planet’s atmosphere. That’s why in the early days of our solar system about 4.5 billion years ago, rocky planets were covered in ocean magma. As the planets cooled and their molten mantles solidified, the process probably released gases into the atmosphere.

These gases were not any chemicals. They were very easily evaporated, chemical elements and compounds. Among the volatiles, hydrogen, carbon, oxygen, and nitrogen, as well as noble gases, are slow elements that do not react with the environment. On Earth, these chemicals eventually led to the development and acceptance of life in our world.

To look for evidence of this process on Mars, Sandrine Péron, a postdoctoral fellow at the ETH Zurich Institute of Geochemistry and Petrology, compared two Martian sources of noble gas krypton. One source was a meteorite that formed in the interior of Mars. The other was a krypton isotope sampled from NASA’s Curiosity Rover from Mars’ atmosphere. Unexpectedly, the krypton signatures did not match. And that could change the sequence of events in which Mars achieved its volatility and atmosphere.

“This is contrary to the standard model of volatile accretion,” says Péron. His findings are described in an article published in the journal Science on Thursday. “Our analysis shows that it’s a little more complicated.”

The planets in our solar system originated from the remnants of our solar birth. The clusters formed a rotating disk of gas and dust, called the solar nebula, around the new star. Some clusters, which accumulated through gravity and collisions, grew large enough to become planets and develop complex geological processes. Others remained small and inactive as primitive asteroids and comets.

[Related: Mysterious bright spots fuel debate over whether Mars holds liquid water]

Scientists believe that in the early stages of the planet’s development, volatile stars entered the new world directly from the solar nebula. Later, as the solar nebula dissipated, more volatiles emerged from the bombardment of chondritic meteorites, small fragments of rocky asteroids that remain unchanged from the early days of the solar system. These meteorites then melted in the magma oceans.

If the atmosphere were provided by space rocks, planetary scientists would expect the volatile atmosphere of a planet to match the most chondritic meteorites, not the solar nebula. Instead, Péron discovered that the krypton in the interior of Mars is almost pure chondrite, while the atmosphere is sunny.

Thus, perhaps Mars was initially bombarded by chondritic meteorites and then solidified while there was still enough solar nebula to form an atmosphere around the hardened red planet, Péron suggests. He explained that the nebula would have formed about 10 million years ago, so the accretion of Mars would have to end within an hour, perhaps in the first 4 million years.

A sample of the Chassigny meteorite that revealed the interior of the Martians contains volatile chondrites. By Sandrine Péron

“Mars seems to have created its atmosphere from the primordial gas that passed through the solar system,” said Matt Clement, a postdoctoral fellow at the Carnegie Institution for Science who did not participate in the study. “Overall, it matches our picture. We believe that Mars formed much, much faster than Earth. ”

Scientists often look to Mars to study the early solar system, which is believed to have been created very quickly. Mars, which is one-tenth the size of Earth, is much less geologically active, which means that the Red Planet probably retains many of the conditions of the first days of our planet’s neighborhood.

However, to study the chemistry of Mars, scientists need to send mechanical messengers like Curiosity Rover to the planet, or break it, launch it into space, and examine the parts of Mars that have landed on the Earth’s surface. There are only hundreds of meteorites like this.

The meteorite studied by Péron is unique. In 1815, it fell through the Earth’s atmosphere, breaking into pieces on the French Chassigny. Since then, scientists studying parts of the Chassigny meteorite have determined that it probably came from the interior of Mars, unlike all other meteorites on Mars.

This study highlights how much there is to learn about the formation of the planet, says Clement. “We still don’t quite understand where the volatiles on our planets come from and the pairs of planets that are closest to us,” he says. “The deeper we can measure the better the formation of the planets, the more complicated the process seems to be.”

Clement suggests that each new distinction between Earth and Mars is even more diverse among planets elsewhere. “It simply came to our notice then that different so close to each other, ”he says,“ what strange world can scientists find orbiting other stars?

Leave a Comment