Ever since the ‘70s when it was observed that Mars’s surface shows great differences between its northern and southern hemispheres, scientists have tried to figure out what could have caused the disparity. A series of theories that have tried to explain why the northern hemisphere has far smaller altitudes than the southern one have appeared, but the one that prevailed until recently was the one saying that massive volcanic eruptions that have happened mainly in the southern hemisphere have been responsible for the difference.

However, three new studies that were carried out by researchers at the California Institute of Technology, MIT and NASA’s Jet Propulsion Laboratories, and Santa Cruz and the University of London, seem to tilt the balance in favor of a theory regarding a giant asteroid collision.

Even though the idea is not new, it has been considered improbable until recently because it had been thought that a collision of these proportions would have caused the whole surface of the planet to melt, and that after it would have cooled down, it would have come back to its original shape, if not the original size. This is supposed to be the case of Earth, which is thought to have been hit by an asteroid the size of Mars 4 billion years ago, the impact creating the Moon.

The three new studies have used computer simulations in order to test if a collision that would have pealed the crust off the northern hemisphere would have been possible without the whole surface melting. The simulations have shown that if an object roughly the size of Pluto – which is the size the asteroid would have had – would have hit Mars’s surface at an angle between 30 and 60 degrees, the impact would have led the surface to have the shape it has now. What is more, the shock waves that would have been created would have caused magnetic disturbances in the southern hemisphere, just like the ones that are measured today.

The scientist that made the three studies have said that their work is not capable of giving a final solution to the mystery that surrounds Mars’s shape, and that a special mission to the planet’s surface is needed if more conclusive research is to be made.