The red planet, one of the most studied bodies of the Solar System, door to door in our cosmic neighborhood, may not have always been our neighbor.

A study published in the journal Earth and Planetary Science Letters  postulates that, in fact, Mars formed in the Asteroid Belt, approximately one and a half times farther from the Sun than its current position, before migrating to this location.

About four thousand five hundred million years ago, the Solar System was nothing more than a cloud of dust, and later, rocks, until the fragments were forming the different planets that today make it up. First, the gaseous ones; Today we know that Jupiter is the oldest body in the Solar System. And, later, the rocky ones, like Earth and Mars.

The composition of Mars, more similar to that of meteorites

The widespread belief was that Mars formed close to Earth from the same primitive fragments of the Solar System. But this hypothesis left unanswered questions: why are both planets so different in composition? Mars contains different silicates, lighter than Earth, more similar to those found in meteorites.

Now, this question has a possible answer. In an attempt to explain why the elements and isotopes on Mars differ widely from those on Earth, researchers from Japan, the United States and the United Kingdom conducted simulations to obtain information about the movement of the red planet within the Solar System.

The findings suggest that Mars formed much farther from the Sun than it is now and that Jupiter’s gravitational pull pushed Mars to its current position.

The Grand Tack model

The researchers used the so-called Grand Tack model, which suggests that Jupiter played an important role in the formation and final orbital architecture of the inner planets. 

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The hypothesis holds that a primitive Jupiter, due to its gravitational force, sent a large mass concentration towards the Sun, which contributed to the formation of Earth and Venus. Meanwhile, it pushed material away from Mars, and hence the small mass of the planet (it is 11% of that of Earth) and the difference between the compositions of the two planets.

One implication of the fact that Mars is forming farther from the Sun is that the planet was much colder at birth than originally thought, perhaps too cold for liquid water or to sustain life.

This theory seems to challenge the idea that Mars was much warmer and wetter than it is now. Researchers believe, however, that the activity of the planet Mars could occur later.

According to Stephen Mojzsis, professor of Geological Sciences at the University of Colorado and co-author of the study: “The formation of Mars in the asteroid belt took place very early, long before the crust stabilized and the atmosphere was established.”

In an article he co-authored last year, Mojzsis concludes that, at the end of Mars planetary formation, he was bombarded by asteroids that formed the innumerable craters of the planet. Such large impacts could “have melted the cryosphere and crust of Mars to densify the atmosphere of Mars and restart the hydrological cycle,” he says.


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