After the formation of the Solar System, Mars was not very different from Earth. With an atmosphere and a magnetic field, the Red Planet potentially sported rivers and verdant plains. However, over time, the situation has deteriorated to the point that today the Martian atmosphere, almost non-existent, undergoes continual disintegration due to solar winds. All of this partly because of its lack of a magnetic field. But how did the latter disappear?
Billions of years ago, Mars was a very different place from the arid, parched place it is today. Basically, it had a thicker, warmer atmosphere and liquid water flowing over its surface, and possibly even life. The reason is that, like Earth, Mars had a planetary magnetic field generated by its core. But when this phenomenon disappeared, things began to change drastically.
For years, scientists believed that this field disappeared more than 4 billion years ago, resulting in Mars' atmosphere being slowly stripped by the solar wind. However, according to work conducted by the University of British Columbia (UBC), researchers have placed new constraints on when this magnetic field disappeared, indicating that the magnetic field of Mars existed earlier (and lasted hundreds of millions of years longer) than previously thought.
Like Earth, Mars' global magnetic field would have been the result of a dynamo effect caused by convective motion in its core. This happens when a liquid outer core spins around a solid inner core, in the opposite direction of the planet's rotation. Unfortunately, the magnetic field disappeared, causing the planet's atmosphere to disintegrate to the point of becoming extremely thin (as it is today).
Astrophysicists attribute this to Mars' lower mass and density (compared to Earth), which caused the interior to cool faster. This made the outer core of the planet solid, thus stopping the Martian dynamo effect. Currently, its inner core is believed to be in a liquid state, as the pressure inside Mars is too low to solidify it.
In the past, scientists have relied on studying magnetized rocks on and below the surface of Mars to reconstruct the history of the planet's magnetic field — particularly volcanic rocks. This type of rock originates in the planet's mantle and is then brought to the surface by volcanic activity and resurfacing. As lava is exposed to the surface and cools, its minerals align with the global magnetic field.
After examining magnetized samples of surface rocks, the researchers discovered that a dynamo was active 4.3 to 4.2 billion years ago. However, rock samples taken from three major basins (Hellas, Argyre, and Isidis) — which formed 3.9 billion years ago — have led most scientists to conclude that the dynamo was inactive at that time. there.
But after analyzing the new data obtained by the orbiter Mars Atmosphere and Volatile EvolutioN (MAVEN) from NASA, the researchers got a different picture. New MAVEN data has detected clear evidence of a magnetic field from the Lucus Planum lava flow , which formed about 3.7 billion years ago and showed evidence of a magnetic field. This indicates that a Martian magnetic field existed much later than previous studies in other regions have suggested.
