Analysis of rare meteorite sheds unexpected light on the origin of Mars

(ORDO NEWS) — A small piece of rock that once broke away from Mars and landed on Earth may contain clues that reveal amazing details about the formation of the red planet.

A new analysis of the Chassigny meteorite that hit Earth in 1815 shows that the way Mars got its volatile gases like carbon, oxygen, hydrogen, nitrogen and noble gases is contrary to our current understanding of planet formation.

Planets are born, according to modern models, from the remnants of stellar matter. Stars form from a nebular cloud of dust and gas when a dense clump of matter collapses under the force of gravity. As it rotates, it collects more and more matter from the surrounding cloud in order to grow.

As a result, a disk is formed that rotates around the new star. Inside this disk, dust and gas begin to stick together in a process that causes the baby planet to grow.

We’ve seen other baby planetary systems form in this way, and evidence in our own solar system suggests it formed in a similar way about 4.6 billion years ago.

But how and when were certain elements incorporated into the planets? This data is extremely difficult to put together.

According to current models, volatile gases are absorbed by the molten, forming a planet from the solar nebula.

Because the planet is very hot and soft at this stage, these volatiles are sucked into the global magma ocean, which is the forming planet, and then partly released into the atmosphere as the mantle cools.

Later, volatiles are delivered by bombarding the planet with meteorites. Substances associated with carbonaceous meteorites (called chondrites) are released when they break apart on impact with the planet.

Thus, the inner part of the planet should reflect the composition of the solar nebula, and its atmosphere should reflect mainly the “volatile” contribution of meteorites.

We can tell the difference between these two sources by looking at the isotope ratios of noble gases, especially krypton.

And, since Mars formed and solidified relatively quickly in about 4 million years, compared to 100 million years for Earth, this is a good indicator for those very early stages of the planet formation process.

Of course, only if we can access the information we need – and that is why the Chassigny meteorite was a real gift from space.

Its noble gas composition is different from that of the Martian atmosphere, suggesting that this piece of rock broke away from the mantle (and was ejected into space, eventually falling to Earth), so its composition reflects that of the planetary interior and hence the solar nebula.

However, krypton is quite difficult to measure, so the exact ratio of isotopes eludes measurement. However, Perón and her colleague, fellow geochemist Sujoy Mukhopadhyay of the University of California, Davis, applied a new method using the UC Davis Noble Gas Laboratory to perform a new, accurate measurement of the krypton in the Chassigny meteorite.

The results of the work were extremely .. strange. The ratio of krypton isotopes in the meteorite is closer to the ratio associated with chondrites, and closer significantly. “The Martian interior composition of krypton is almost entirely chondrite, but the atmosphere is solar,” Perón said. “We are sure of it.”

This suggests that meteorites delivered volatiles to Mars much earlier than scientists thought, before the solar nebula was scattered by solar radiation.

Thus the order of events is: Mars acquired an atmosphere from the solar nebula after its global magma ocean cooled; otherwise, the chondrite and nebula gases would be far more mixed than the team observed.

However, this conceals another mystery. When solar radiation eventually burned up the remnants of the nebula, it must have burned the hazy atmosphere of Mars as well.

This means that the atmospheric krypton present later must have been preserved somewhere. The team hypothesized that this “vault” was the planet’s polar ice caps.


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