The magnetic field has been protecting the Earth for 4.2 billion years.
Invisible but essential to life, the Earth’s magnetic field formed much earlier than we thought.
A protective shield
It is a powerful shield that protects the Earth from harmful effects of the highly energetic particles carried out by the solar winds and those which come from other stars way more distant. Without a magnetic field surrounding the planet, life would be impossible and its ocean would likely have evaporated into space. The blue planet would then probably have lost its nickname and would look like Mars.
Scientists at the University of Rochester in the USA have broken the record for the age of the Earth's Magnetic field with the discovery of its existence 4.2 billion years ago. They found traces of it by studying zircon crystals, collected in Australia, and dated from 3.2 to 4.2 billion years ago. These materials, which are among the oldest on Earth, contained magnetite’ particles, even smaller, oriented in a very precise direction, the one of the early magnetic fields which reigned on Earth during this period, shortly following the formation of the planet.
How is it generated ?
Today it is the movements of Earth’s outer core (a fluid layer) around the solid seed which occupied its center that generate and maintain the magnetic field. But four billion years ago this solid core did not exist. Another mechanism came into play to generate the magnetic field.The researchers who published their results in the PNAS, believe that it is the precipitation of cooled materials in the heart of the Earth that fed the dynamo of the planet and formed its protective shield.
