Billions of years ago, the surface of Earth was more similar to a hellish landscape instead of what we know today. Surface temperatures would have killed almost everything, the air was filled with dangerous gasses, and a large amount of solar radiation went through the atmosphere without issues.
An unexpected layer of protection came from the Moon, which kept the brunt of the solar wind away from the surface, allowing the young planet to improve its atmosphere in the meantime.
The genesis of the Moon
More than 4,5 billion years ago, a massive object called Theia crashed into an Earth that was less than 100 million years old. Some of the debris that was released by the impact formed the Moon while others were absorbed by the surface of the planet. As the Moon formed, Earth started to spin at a slower speed.
The Moon’s influence over the oceans leads to an energy release, pushing the object away from Earth by 1.5 inches every year. This may not seem like much at first sight, but the Moon used to be three times closer in the past.
A shared magnetic shield
Recent studies have showed that the Moon used to have a magnetosphere, a theory which was reinforced by samples that were tested with the help of modern scientific tools. A computer model was created to observe how the magnetic fields of the Moon and Earth may have interacted.
The magnetosphere of the Moon and Earth also seems to have been connected near the polar regions, a link that was great for Earth as it prevent solar winds from stripping the atmosphere away. Earth may have also helped the Moon to maintain a thin atmosphere for a short amount of time.
It is estimated that the share magnetic field could have lasted for up to 600 million years. More information could be uncovered in the future.