The analysis of the data produced by NASA Lander Insight identified in the depths of Mars fragments dating back to earthquakes that took place 4.5 billion years ago.
Fragments dating back to colossal impacts occurred on Mars 4.5 billion years ago were identified in the depths of the planet. To detect them was the NASA Lander Insight, now no longer operational, which collected the data before the conclusion of the mission in 2022.
According to the researchers, those ancient shocks released an energy such as to merge entire portions of the crust and the primordial cloak, creating vast oceans as continent and dragging debris and fragments of the impact in the bowels of the planet.
Slow evolution. It is not possible to establish with certainty what Mars hit: the young Solar System was populated by many rocky bodies, including protopynetes of considerable size. Today, the remains of those violent impacts survive in the form of rock masses in diameter up to 4 kilometers scattered in the Martian cloak.
A testimony that only worlds like Mars can keep: unlike the earth, without plaque tectonics, the interior of the red planet has not been shuffled by the convection process. The discovery was described on Science. “We had never observed the interior of a planet with this level of detail and clarity,” explained Constantinos Charalambous of the Imperial College of London, the first author of the study. «What we see is a cloak dotted with ancient fragments: the fact that they survived to date indicates that the evolution of the Martian cloak has been slow and gradual. On earth, however, such structures would have been canceled for some time ».
Insight’s contribution. The Lander, managed by the Jet Laboratory (Jpl) Jet of the NASA in California, placed the first seismometer never installed on the planet in 2018 in 2018. The extremely sensitive tool recorded 1,319 earthquakes until the end of the mission in 2022. Seismic waves, modifying themselves as they cross different materials, have allowed scientists to study crust, cloak and core of the planet. The analysis of the data has already made it possible to define its size, depth and composition.
The new discovery on the cloak confirms how much there is still to be discovered in the data collected. “We knew that Mars was a sort of capsule of the time of his primordial formation, but we did not expect to be able to read it so clarity thanks to Insight,” added Tom Pike, co -author of the study and colleague of Charalambous to Imperial College.
Hunt for earthquakes. Mars, unlike Earth, does not have the busty plaques. Yet here too there are earthquakes, due to two main causes: the fracture of the rocks under the effect of heat and pressure, or the impact of the meteoroids.
Precisely the latter, according to a study published on Geophysical Research Lettersproduce high frequency seismic waves capable of crossing the crust until they reach the cloak, a layer of solid rock often up to 1,550 kilometers and with temperatures that can touch 1,500 ° C.
Enigmatic signals. In the study just published on Sciencethe authors identified eight earthquakes whose high frequency waves were strongly altered after crossing the cloak. “Initially we thought the slowdowns were due to the crust,” said Pike. “Then we realized that the more deeply the waves traveled, the more the signals were slowed down.” Through planetary simulations on the computer, the team discovered that these delays occurred only in small localized areas, consisting of different composition material compared to the surrounding cloak.
But how did those lumps arrive there? Going back billions of years, the researchers concluded that they were enormous asteroids or other rocky bodies to hit Mars, generating oceans of magma and dragging fragments of crust and cloak in depth. Charalambous compares the resulting structure to the shattered glass: few large pieces and a myriad of splinters, an image consistent with the release of energy produced by impacts of that type.
A natural laboratory. On earth, plaque tectonics continually recycles crust and upper cloak: the cold and dense areas sink, the warm and less dense ones go back. On Mars, however, the absence of plates causes the interior to move much more slowly, preserving structures that would otherwise have disappeared. “The fact that we can still observe them,” said Charalambous, “shows that Mars has not undergone a vigorous remission”. The red planet could therefore also offer clues to what is hidden under the surface of other rocky worlds without plaque tectonic, such as Venus and Mercury.
