In the 70s, the Viking probesent by NASA to study Mars, took some images and measurements that demonstrated a very curious fact on the red planet. They saw that this is divided into two very clear parts. The southern area is full of craters and lava flow marks, while the northern area is flat and smooth. Furthermore, the southern zone has a difference in altitude with the north of about 5 or 6 kilometerswith the southern area being the highest. This clear difference between one half and the other was named martian dichotomy and its origin has been a mystery ever since.
There were mainly two hypotheses: the endogenous and the exogenous. The balance did not seem to lean towards either. However, thanks to the module Insight, sent by NASA to Mars in 2018, enough data has finally been obtained to point in a direction.
It has been possible thanks, on the one hand, to seismograph located between the spacecraft’s instruments and, on the other, at its landing location, very close to the border that separates the two halves of the Martian dichotomy.
Two hypotheses for the Martian dichotomy
The Martian dichotomy does not consist only of what has been described so far. There is even more heterogeneous data between the two halves of Mars. For example, the bark of the southern area is thicker and its rocks have magnetism, which indicates that they belong to a time when this planet had a global magnetic field.
There are scientists who believe that this may have an external origin, due to the impact of a large object that suddenly altered the orography of the planet. That is the exogenous theory. On the contrary, other scientists consider that it may be due to the flow of heat that occurs from the hottest to the coldest areas of the planet’s interior. They are the defenders of the endogenous theory.
Insight holds the key
Insight’s challenge in analyzing earthquakes on the Red Planet is enormous. As well explained in an article for The Conversation one of the researchers who have analyzed their data, Hrvoje Tkalčić, Earth is full of seismographs spread throughout the planet, while on Mars everything is bet on the effectiveness of Insight.
The seismograph on board the lander identifies the S and P waves, associated with ground vibration, and by measuring the time difference between them, it locates the location of the earthquakes.
P waves are what are known as primary, while S waves are secondary. They receive this name because the Ps are much faster, so they reach the seismographs. Since we know the approximate speed at which each one moves and the difference between them, the time that passes between the arrival of one and the other helps to calculate the distance between the center of the earthquake and the instrument that has located it. the vibrations. This applies to Earth, Mars or any planet with earthquakes.
On the other hand, by analyzing the movement of particles in the ground, we can know the direction of the earthquake.
The winning hypothesis of the Martian dichotomy
With this information and other data from satellite cameras, it was possible to locate a earthquake group in the southern highlands that would serve to further study the Martian dichotomy. Afterwards, another interesting group of earthquakes was located in the northern lowlands.
Once this was done, the Insight mission scientists studied how the S waves lost energy as they spread through the rock in each part of the planet. It was seen that the waves were losing energy much faster in the southso it can be intuited that the underground rock in this area is much hotter. Those responsible for the research believe that the Martian dichotomy may be due to a combination between this temperature difference and a blockage of the movement of tectonic plates that took place at some point in the red planet’s past. This would leave the planet divided, like when the lid of a container gets stuck incorrectly.
In short, with this new research, the endogenous hypothesis about the Martian dichotomy wins. All thanks to a ship that flew to Mars in 2018. It has taken many years, but at least it seems that the mystery is almost solved.
