An article published in “Geophysical Research Letters” describes a study that attributes to a gigantic meteoric impact on Mars’ northern hemisphere almost 4.5 billion years ago some of the red planet’s features. According to Stephen Mojzsis of University of Colorado Boulder and Ramon Brasser of Tokyo Institute of Technology in Japan that’s the cause of the presence of rare metals, of the differences between the northern and southern hemisphere and perhaps even the existence of its two moons.
The theory of the impact of a giant asteroid or even of a dwarf planet with Mars when it was very young is not at all new since it’s about 30 years old. Various researchers performed increasingly sophisticated simulations to try to reproduce that event and they became more and more convincing. Geological Sciences Professor Stephen Mojzsis decided to study the elements that make up Mars to get more answers and to do it he worked with astronomer Ramon Brasser.
The two scientists studied samples of Martian meteorites and realized that there’s an abundance of rare metals such as platinum, osmosis and iridium in the planet’s mantle. Under normal conditions those elements get absorbed into the metal core of rocky planets but in the case of an impact with a particularly large asteroid things might go differently.
To make new computer simulations, the two scientists estimated that those elements found in Martian meteorites account for about 0.8% of Mars’ mass. At that point, they created a series of simulations with asteroids of different sizes to figure out the characteristics a meteorite should have to have that amount of metal left on Mars.
The best results came by simulating the impact of a dwarf planet with a diameter of at least 1,200 kilometers (745 miles) – larger than Ceres – which occurred about 4.43 billion years ago, followed by minor impacts. That kind of impact would also change Mars’ crust causing the differences between the two hemispheres. According to Stephen Mojzsis, the northern hemisphere’s crust appears younger and this could confirm that theory.
An impact of this kind projects materials into orbit, generating a ring around the planet. It’s possible that those materials formed Deimos and Phobos, the current Mars’ moons. This would explain the variety of elements that form them, which so far made it difficult to determine its origin and the reason why many scientists think that those are asteroids captured by the red planet.
Stephen Mojzsis and Ramon Brasser intend to keep on studying the composition of Martian meteorites to better understand the Mars’ mineralogy and new possible details of the impacts suffered by the red planet. Reconstructing events that happened nearly 4.5 billion years ago is difficult but if the consequences are so dramatic that they leave traces even after such a long time they can do it. Surely the issue is not entirely resolved and there may still be discussion and model refinement with new discoveries.