One of the most famous features of the red planet is its asymmetry. The southern hemisphere and equatorial regions of Mars are an ancient and densely cratered surface. The northern hemisphere of the planet is mainly occupied by a gigantic lowland (Great Northern Plain) 10,600 long and 8,500 kilometers wide. Its average height is six kilometers lower than the rest of the surface of Mars. Some scientists have already suggested that the Great Northern Plain is the trail of a giant collision that the planet experienced shortly after its formation. Recently, a study was published in the journal Geophysical Research Letters supporting this theory.
In 2011, a meteorite was found in the Sahara Desert, called the "Black Beauty". According to the results of isotopic analysis, the stone is of Martian origin. It was knocked out of the surface of the red planet 4430 million years ago. Chemical analysis of the "Black Beauty" showed that it contains a fairly large amount of siderophilic elements, including iridium, platinum and gold.
According to modern concepts, after the formation of planets (including the Earth) and the differentiation of their depths, gold, platinum and other similar elements descended to the core. The bulk of the heavy elements now in the crust and mantle got there along with the asteroids.
Last year, scientists at the Tokyo Institute of Technology published an article explaining the chemical composition of the Black Beauty to the effects of a collision of Mars with a very large object in the first 130 million years of its life. Now, a group of researchers from the University of Colorado at Boulder tried to answer the question of what were the dimensions of such a body. They created a series of computer simulations and concluded that the object had a diameter of about 1200 km, which is larger than Ceres. Such a collision should have left a giant crater on the surface of the red planet, comparable in size to the Great Northern Plain.
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Another consequence of such a blow would be a large amount of debris thrown into space. As you know, Phobos and Deimos do not at all fit into the usual classification of planetary satellites. Both bodies are very similar to asteroids. But if Phobos and Deimos were indeed captured by the planet's gravity, their orbits would not be circular and would not lie in the plane of the Martian equator. At the same time, the structure and size of small moons indicate that they did not form with Mars. The most likely explanation for all these oddities is that both bodies formed in orbit of the planet from debris ejected after a major collision.
Thus, the big collision theory can explain the asymmetry of Mars, the chemical composition of its meteorites and the origin of satellites. Its confirmation could be the analysis of the soil of Phobos or Deimos. If the theory is correct, they should be made up partly of Martian matter and partly of asteroid material.