The existence of a diverse atmosphere on our planet is crucial for life. On top of being in the Goldilocks zone, our Earth has another life-supporting feature that is much less discussed in the popular science media: a sufficiently-strong geomagnetic field. Without it, the Earth's upper atmosphere, including the Ozone layer, can be wiped away by solar wind, and DNA-damaging cosmic rays can strike the surface of our planet without much resistance.
According to a recently published study, a team of U.S. researchers discovered exciting geological evidence that can help us date the earliest presence of Earth's magnetic field and measure its intensity in the primordial time of our world.
They conducted paleomagnetic analyses, mainly the orientation and intensity of trapped magnetic minerals, on zircons samples collected from the Jack Hills in Western Australia. This crust-bound, zirconium-based rock plays an indispensable role in a technique known as radiometric dating, which allows scientists determine the age and the history of rock formations.
Combined with data from electron microscopy and geochemical tests, their results placed the earliest existence of Earth's geomagnetic field at about 4.2 billion years old. What's more, they also demonstrated that the magnetic field might had reached twice its current strength around 3.2 billion years ago, and it was at its weakest point between 3.4 and 3.6 billion years ago.
Although the researchers cannot pinpoint what caused the geomagnetic field to exist in the first place, they suspect that it must be related to the lunar-forming giant impact, which happened just a few hundred million years before its origin.
Source: Anton Petrov via Youtube