A meteorite confuses the theory of Mars formation

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[EN VIDÉO] The planets of the solar system were born from cataclysms
The earth and the other planets revolving around the sun were accidentally born in turmoil by successive collisions. This is what describes this episode of the Keys to the Universe series offered by the Discovery Science channel.

Studying meteorites found on Earth makes it possible better understand the formation of our planet and its sisters Mercury, Venus and Mars. True relics of origin solar systemMeteorites, in particular, help scientists determine their original composition rocky planets and in particular the type and the origin of volatile elements which go into the composition of rocks and took part in the formation of our the atmosphere.

Formation of rocky planets: nebulae or chondrites?

The current hypothesis on the formation of rocky planets suggests that these volatile elements entered the solar nebula early in formation from the young planets. At this point, the earth is but the others rocky planets there were only stone balls in it merger. Volatile elements such ashydrogenthe carbonI’oxygenI’nitrogen and many gas rare, were thus absorbed and dissolved in the ocean magma occupy their surface. Then through the volcanism In the intensive that followed, these gases formed an atmosphere. The young planets were then subjected to a long and intense bombardment by meteorites known as ” chondrites », who were also involved in the contribution of volatile elements. The idea is also that it’s the volatile elements of meteorites that contributed most to the formation of the atmosphere, at least the terrestrial one.

From this hypothesis it follows that the composition of the primitive solar nebula or nebula-meteorite mixture would be found mainly at the level of the innermost layers of the earth. The deep parts of the mantle are more likely to have retained this chemical signature. that the more superficial layers have undergone an intensive melting process over billions of years and degasing. However, a new study breaks this paradigm.

A meteorite testifying to the internal composition of Mars

Meteorites that fall to Earth can come from many sources, including the surface of other rocky planets around the world. solar system. Indeed, the violent impacts that hit the various planets early in their lives threw out planetary fragments that still regularly collide with neighboring planets. This is how fragments of Martian rocks were found on Earth. However, one of these meteorites has special value for scientists because it would not have come from the surface but from the interior of Mars, an extremely rare fact. it’s about the meteorite de Chassigny, discovered in France in 1815.

A team of researchers has studied the composition of this meteorite and in particular the origin of its volatile elements. Analysis of krypton’s isotopic ratios usually makes it possible to distinguish the solar or chondritic origin of the volatile elements. And the results of the study of the Chassigny meteorite are surprising, to say the least.

In fact, isotopic analysis shows that the volatile elements it contains do not derive from an assimilation of components of the solar nebula, as we thought, but from an integration of chondritic material. This implies that the chondrites participated in the contribution of volatile material much earlier than we thought, namely at the time of the planet’s formation from the solar nebula.

It could even be that the situation is completely reversed, associating the planet’s internal composition with the chondrites and that of the atmosphere with the solar nebula.

The atmosphere of Mars would have formed very quickly

The article that just appeared in the review Scienceindicates in any case that the atmosphere of Mars could not have formed solely through the degassing of Mars a coat, which should then have had a chondritic composition. It is possible that the planet obtained its atmosphere very early, integrating the elements of the solar nebula, before the magma ocean cooled. It should be noted that Mars solidified very quickly, in just 4 million years, even if this duration is discussedunlike Earth, which took between 50 and 100 million years to cool down.

These new results suggest that Mars’ growth would have ended before the solar nebula dissipated under the action of the young’s radiation Sun.

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